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�HIGHER INSTITUTE OF MINING AND METALLURGY OF MOA
READING SELECTIONS FOR MECHANICAL ENGINEERING
STUDENTS
ENGLISH IV
AUTHORS:
M. Sc. MIRTHA ODALIS OLIVERO HERRERA
M. Sc. GEORGINA AGUILERA SABORIT
M. Sc. ADIS FIOL CUENCA
M. Sc. ADELFA VERDECIA CRUZ
M. Sc. MARIO ANDRÉS NAVARRO CONSUEGRA
Lic. RICHEL FERNÁNDEZ MORA
Lic. YANISEL BATISTA NUÑEZ
Lic. ALIUSKA HINOJOSA CALA
�Página legal
Título de la obra: Reading selections for Mechanical Engineering students. English IV,
69 pp. Editorial Digital Universitaria de Moa, año 2018 -- ISBN: 978-959-16-4174-8
1. Autor: Mirtha Odalis Olivero Herrera
2. Institución: Instituto Superior Minero Metalúrgico «Dr. Antonio Núñez Jiménez»
Corrección: Dr. C. Tania Bess Reyes
Diseño: Wilkie Villalón Sánchez
Institución de los autores: ISMM «Dr. Antonio Núñez Jiménez»
Editorial Digital Universitaria de Moa, año 2018
La Editorial Digital Universitaria de Moa publica bajo licencia Creative Commons de
tipo Reconocimiento No Comercial Sin Obra Derivada, se permite su copia y
distribución por cualquier medio siempre que mantenga el reconocimiento de sus
autores, no haga uso comercial de las obras y no realice ninguna modificación de ellas.
La licencia completa puede consultarse en:
http://creativecommons.org/licenses/by-nc-nd/4.0/
Editorial Digital Universitaria
Instituto Superior Minero Metalúrgico
Ave Calixto García Íñiguez # 75, Rpto Caribe Moa 83329, Holguín Cuba
e-mail: edum@ismm.edu.cu
Sitio Web: http://edum.ismm.edu.cu
�Preface
Este folleto presenta una selección de textos de la literatura técnica que los
estudiantes de la carrera Ingeniería Mecánica encontrarán durante su
aprendizaje en la universidad y durante el desarrollo de su profesión. Con ello,
se complementan folletos anteriores en los que se enseñan los aspectos
gramaticales y el vocabulario general y técnico requerido para comprender el
idioma inglés con fines profesionales en una forma adecuada para este nivel de
enseñanza.
Se presenta, además, un glosario en inglés de términos tomados del
vocabulario técnico de mayor uso en libros relacionados con la especialidad.
Asimismo, teniendo en cuenta que el objetivo principal de la asignatura Inglés
es leer y comprender literatura técnica en este idioma, se concibió la
ejercitación para que los estudiantes se apropien de un sistema de
conocimientos que puedan generalizar y aplicar posteriormente.
�Index
Preface
Page
!!!
Theme 1: Strength of Materials
Reading A: Strength of Materials (Problems and Methods
1
Reading B: Strength of Materials (Assumptions 1 and 2)
5
Reading C: Strength of Materials (Assumptions 3, 4, 5 and 6)
11
Reading D: Ductility and Brittleness. Hardness
17
Reading E: Beams-Shear forces
20
Theme 2: Machines
Reading A: Automatic Control of Machine Tools
24
Reading B: A car wash for cleaner air
27
Reading C: Kinematic
30
Reading D: The Centre Lathe
35
Theme 3: Thermodynamic
Reading A: Thermodynamics system
40
Reading B: Thermodynamics reversibility
45
Reading C: The subject of Hydraulics
49
Theme 4: Cavitations
Reading A: Cavitations
54
Complementary Texts
Reading A: Historical Perspective
59
Reading B: Some criteria to select the appropriate material
60
Glossary
62
�Theme 1: Strength of Materials
Reading A: Strength of Materials (Problems and Methods)
I. Before you start reading
Rate your knowledge of key vocabulary on this topic. Write an (X) next to the words you
can give their Spanish equivalents. Notice the grammatical category (part of speech) in
parentheses beside each word in the list. *
___ science (n)
___ relegate (v)
___ property (n)
___ stiffness (a)
___ background (n)
___ deformable (a)
___ use (v)
___ irrelevant (a)
___ place (n)
___ design (n) (v)
___ section (n)
___ body (n)
___ machine (n)
___ treat (v)
___ reliable (a)
___ motion (a )
___ deal (v)
___ branch (n) (v)
___ ability (n)
___ strength (n)
___ cumbersome (a)
* (a) = adjective
(n) = noun
(v) = verb
II. Look up the new words in a bilingual dictionary and write them down in your notebook.
III. Fill in the blanks with the corresponding word from the previous list.
a) Stiffness and __________ are properties of materials.
b) Strength is the _________ to resist deterioration.
IV. Read the list of words provided again. Taking into account their meanings and
relationships, can you predict what the title of the text will be?
Reading A: Strength of Materials (Problems and Methods)
From «Strength of Materials»
By P. Stepin
The necessary, i.e., reliable dimensions strength of materials is the science of resistance
and stiffness of elements of engineering structures. The methods of this science are used
in design practice to determine of machine parts and various structural members.
1
�The fundamental principles of strength of materials are based on the laws and theorems
of general mechanics and in the first place on the laws of statics without the knowledge
of which the study of strength of materials is inconceivable.
In contrast to theoretical mechanics, strength of materials deals with problems in which
emphasis is placed on the properties of deformable bodies while the laws of motion of a
body as a whole are not only relegated to the background but in some cases are
altogether irrelevant. At the same time, due to the generality of its fundamental principles
strength of materials may be regarded as a section of mechanics which is called
mechanics of deformable solids.
Mechanics of deformable solids includes also other branches, such as the mathematical
theory of elasticity which treats essentially the same problems as strength of materials.
The difference between strength of materials and the mathematical theory of elasticity
lies primarily in the approach to the solution of problems.
In the mathematical theory of elasticity which also studies the behaviour of deformable
solids the problems are stated more rigorously. Hence the solution of problems in many
cases calls for a complex mathematical apparatus and frequently involves cumbersome
computational operations. In consequence the possibilities for practical application of the
methods of the theory of elasticity are limited. On the other hand, a more comprehensive
analysis of the various phenomena is attained.
Exercises
I. Begin reading
I. Synonyms: From this list, choose a synonym for the word in bold type in each
sentence. Use appropriate tenses for verbs and singular or plural forms for nouns. You
can use the dictionary.
Embarrassing
Rigidity
Apply
Quality
Equipment
Failure
1. The ability to resist deformations is called stiffness.
2. The ability to resist deterioration is called strength.
2
�3. The methods of strength of materials are used to determine of machine parts.
4. Stiffness and strength are properties of materials.
5. Hence the solution of problems in many cases calls for a complex mathematical
apparatus and frequently involves cumbersome computational operations.
II. Complete the following cooperative crossword puzzle. Work in pairs. In order to solve
this crossword puzzle, you will have to cooperate with your partner. You have only the
definitions and your partner has the puzzle. Read, and if necessary, explain the definition
when your partner asks. You may not look at the puzzle and your partner may not look at
the definitions. In other words, you may cooperate verbally but not visually!
1
2
3
4
5
6
9
10
7
8
3
�Across
1- A
Down
synonym
of
«embarrassing»,
2- A word meaning «Entre» in English.
«troublesome» (parag. 5)
(parag. 4)
5- The word that expresses «Ley» in
3-Something that is «trustworthy»,
English. (parag. 2)
«dependable» (parag. 1)
10- A verb meaning «lograr», «alcanzar»
4- The ability to resist deformation, rigidity
in English (in simple past). (parag. 5)
(parag. 1)
6- The antecedent of the word
«Application»
7- The word that means «Mientras» in
English (parag. 3)
8- Distortionable (parag. 3)
9- Figure (in plural) (parag. 3)
II. Keep on reading
I. Scan through the text to find the answers to these questions (You may be asked to
talk about this in the practice session with your classmates and your language
professor).
1. Where are the methods of Strength of materials used in?
2. What are the main principles of Strength of materials based on?
3. What are the branches of mechanics of deformable solids?
4. What is the difference between Strength of materials and The Theory of Elasticity?
5. What does The Theory of Elasticity study?
II. Scan through the text and write a summary in English.
4
�Reading B: Strength of Materials (Assumptions 1 and 2)
I. Before you start reading
I. Fill in the blanks to complete these definitions using words from the list.
a) What is a rod?
A rod is a _________ with one dimension _________ than the other _________.
List: two, bigger, body
b) What is a block?
A block is a body with three ____________ in the _________order.
List: same, dimensions
STRENGTH OF MATERIALS (Assumptions 1, 2)
From «Strength of Materials»
By P. Stepin
Most of the structures an engineer has to deal with are very complicated in form, but their
individual elements can be reduced to the following simplest types.
A rod is a body, two dimensions of which are small as compared with the third (fig. 1a).
In a particular case a rod may have a constant cross- sectional area and a straight-line
axis. The axis of a rod is a line passing through the centroids of its cross sections. A rod
with straight- line axis is often called a bar.
a)
c)
5
�b)
Fig. 1
d)
A plate is a body bounded by two flat surfaces, the distance between which is small
as compared with the other dimensions. (fig. 1b)
A shell is a body bounded by two curvilinear surfaces, the distance between which is
small as compared with the other dimensions. (fig. 1c)
A block is a body, where three dimensions are in the same order. (fig. 1d)
Engineers are primarily concerned with bodies having the form of rods of constant rod
sections, and the simplest systems composed of such rod. They deal with rods having a
considerable degree of stiffness, i.e., rods which do not become noticeably deformed
under load.
In very slender bars, such large deformation occurs, that they cannot be disregarded,
even in determining the reaction of support.
Methods of analysis of slender bars, plates, shells and blocks, are treated in a subject
called theory of elasticity, free of the simplifying hypothesis which is introduced in a study
of strength of materials. The methods of the theory of elasticity provide exact solutions of
problems treated in a course on strength of materials, as well as solutions of more
complicated problems, where it is not possible to state applicable simplifying hypothesis.
Methods of designing bar systems are studied in the theory of structures also known as
structural mechanics.
Assumptions in Strength of materials
In view of the complexity of structural analysis certain simplifying assumptions are made
concerning-properties of materials, loads and the nature of the interaction of a part and
loads. Experimental verifications of design relations, obtained on the basis of the
6
�assumptions, given below, show that the resultant error is so insignificant that for
practical purposes it can be neglected.
Assumption 1
The material of a body has a solid (continuous) structure.
This is fully justified form the practical point of view as most structural materials have
such fine- grained structure that they can be considered solid, continuous, without giving
rise to appreciable error. Calculations give satisfactory results in practice even for such
materials as timber, concrete and stone.
This is due to the fact that the dimensions of real parts are many times greater than
interatomic distances. This assumption makes it possible to employ a method of
analysing infinitesimal volumes for which the mathematical apparatus of continuous
functions may be used and to apply the results obtained to real specimens.
Assumption 2
The material of a part is homogeneous. i.e., it has identical properties at all points.
Metals posses a high degree of homogeneity, i.e., they have practically the same
properties throughout a part. Timber, concrete, stone and reinforced plastics are less
homogeneous.
Concrete contains an aggregate - small stones, gravel, brick – the properties of which
are different from those of cement.
In timber there are knots; in plastics, the properties of a resin differ from those of a filler.
Nevertheless, calculations based on this assumption, give satisfactory results for main
structural materials.
II. Begin reading
III. Expand your vocabulary. Scan through the text and find the equivalent to:
a) centro de gravedad____________________________________
b) eje rectilíneo_________________________________________
c) superficie llana_______________________________________
7
�d) trata con____________________________________________
e) propiedades de los materiales____________________________
f) de granulación fina_____________________________________
g) debido a _____________________________________________
h) muestra, tipo__________________________________________
i) no obstante____________________________________________
IV.
Scan through the text and complete the following chart taking into account the
similarities and the differences of these materials.
Materials
Similarities
Differences
Stone
Concrete
Timber
Reinforced
plastics
V. Scan through the text again and write out of the reading:
a) Two sentences with connectives of addition.
b) Two sentences with connectives of concession, contrast and opposition.
c) Two sentences with connectives of cause, motive and reason.
8
�d) Two sentences with connectives of purpose.
VI.
Scan through the text and try to organize these ideas in order of appearance in the
text.
a) _____A shell is a body whose surfaces are curves.
b) _____The material of a body has a continuous structure.
c) _____Calculations give satisfactory results for structural materials.
d) _____Concrete is a material made of cement and gravel.
e) _____The majority geometric forms of the structures in engineering are
complicated.
9
�V. Read the text and draw information related to:
Types to which individual structural elements
can be reduced
The advantages of the theory of elasticity
The purpose of assumptions in Strength of
materials
III. Keep on reading
I. Two Mechanical Engineering students are studying about Strength of Materials.
Complete this short dialog for you to know.
John: Jimmy, can you help me to complete this exercise? Do you know what the ability to
resist deformations is?
Jimmy: Yes, of course. It is called____________________.
John: And, what a body whose surfaces are curve is?
Jimmy: It is called________________. Now, it´s my turn to ask. What are the changes in
shape and dimensions called?
John: I think they are called__________________.
Jimmy: I think I have a difficult question for you. Can you tell me what a body with one
dimension bigger than the other two is?
John: Wow! It´s too easy. It´s called_________________.
And what is a wooden
material with knots?
Jimmy: It´s called______________________.
List: deformations, timber, concrete, stiffness, rod, shell.
II. Make a brief summary of the text in English.
10
�Reading C: Strength of materials (Assumptions 3, 4, 5 and 6)
I. Before you start reading
a) Fill the blanks with words from the following list following the sentences.
1. When
a
material
has
the
same
properties
in
all
directions
it
is
called_____________.
2. The internal forces are also called forces of __________________.
3. Non-uniform cooling can induce internal forces in ________________ parts.
4. The principle of superposition can be used with deformable bodies only
under________________ conditions.
5. The word __________________ is used to express the difference between the
initial position of a body and any later position
a) elasticity
b) steel
c) certain
d) displacement
e) prior
f) isotropic
g) level out
h) as well
Reading C: Strength of materials (Assumptions 3, 4, 5 and 6)
From «Strength of Materials»
By P. Stepin
Assumption 3. The material of a part is isotropic, i.e., it has identical properties in all
directions.
The crystals of which many materials consist have quite different properties in different
directions. Cooper crystals are more than three times as strong in one direction than in
another. However, in fine-grained materials the properties in different directions become
uniform, they «level out» due to the disorderly arrangement of a great number of
crystals, and these materials an be considered, virtually isotropic.
11
�For such materials as timber, reinforced concrete and plastics, the above assumption is
only approximate.
Such materials, whose properties are different in different directions, are called
anisotropic.
In the solution of some problems concerning for example, plastics, it is necessary to take
into account the anisotropy of the material by the application of the methods in the theory
of elasticity.
Assumption 4. There are not internal (initial) forces in a body prior to loading.
The forces of interaction between the particles of a material, the distances between
which vary, resist
changes in the shape and dimensions of the body under load.
Henceforth, speaking of internal forces (or forces of elasticity) we shall have in view just
these forces (stresses), without taking into account the molecular forces existing in
an unloaded body as well. Stress-strain
This assumption is not, strictly speaking, true of a single material.
In steel parts sometimes there exist internal stresses induced by non-uniform cooling,
and in timber by non-uniform drying; in concrete they arise during setting.
The
magnitude of these forces (stresses) is important to be known by a designer. When there
is reason to suppose that these forces (stresses) are considerable, an attempt is made
to determine them (experimentally).
Assumption 5. The principle of superposition
The effect of a system of forces acting on a body is equal to the sum of the effects of
these same forces applied to the body in succession and in any order.
The word «effect» implies deformation, internal forces produced in a body and
displacements of individual points, depending on the particular case.
It should be born in mind that the action of the separate forces of a system should be
considered in conjunction with the corresponding reactions of constraints.
The principle of superposition, extensively used in theoretical mechanics for absolutely
12
�rigid bodies, can be applied to deformable bodies only under the following conditions:
1. Displacements of the points of application of forces are small compared to the
dimensions of the body.
2. Displacements resulting from the deformation of a body depend linearly on the acting
forces.
In ordinary structures both these conditions are fulfilled and therefore the principles of
superposition are widely used in structural design.
Assumption 6. On Saint- Venant´s principle. At points of a body, which are sufficiently
distant from the places of application
depends to a very small extent
of loads,
the magnitude of
internal
forces
on the particular manner in which these loads are
applied.
This principle allows the replacement of one system of forces by another, statically
equivalent system which may simplify the analysis.
II. Begin reading
I. Expand your vocabulary.
I. a) Complete the chart with the missing word in each corresponding column. The first
one has been done for you.
Verb
load
Noun
loading
Adjective
loaded
considerable
corresponding
concerning
apply
forces
Comparison, comparative
structure
13
�I. b) Complete each sentence with one of the words from the chart. Nouns could be used
in singular or plural. Verbs in any tense.
a) There aren´t initial _____________ in a body before loading.
b) We have to keep in mind the _______________ of the methods because the
properties vary.
c) It is important to make a _______________ design for the conditions to be
accomplished.
II. Expand your vocabulary. Match the words in column A with their definitions in column
B.
A
Isotropic
Principle of superposition
Initial forces
Anisotropic
B
__ can be put into practice on distortionable bodies
taking into account certain conditions
__when the material has the same qualities in all
directions
__are also called internal
__ when the material has different qualities in
different directions
III. Try to find words related to the technical vocabulary studied in class. They can be in
14
�all directions. Then complete the sentences.
A
B
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H
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1. The change in shape and dimension is called ________________.
2. Deformable_____________are called real bodies.
3. The ability to resist failure is called ____________.
4. A _________ having a straight axis is called ___________.
5. ___________ is a wooden material with knots.
6. The material made of cement and gravel is called _____________.
7. A ___________ is a body which has no difference in its dimensions.
8. A body limited by even surfaces is called ___________.
9. A ____________ is a body whose surfaces are curve.
10. The principle of _______________can be used with deformable bodies only under
certain conditions.
11. When a material has the same properties in all directions it is called_______.
15
�IV. First unscramble the letters to make words. The clues or simple definitions will help
you.
ORTCIPOSI
REMTIB
FSTIFENSS
ETNOCREC
1. It can be put into practice on distortionable bodies taking into account certain
conditions.
2. Wooden material with knots.
3. It is a property of metals.
4. Material made of cement and gravel.
Next use the circled letters to form another word
5. It is a material used for making concrete.
16
�III. Keep on reading
I. Scan through the text to find the answers to these questions (You may be asked to talk
about this in the practice session with your classmates and your language professor).
a) What is the meaning of isotropic?
b) Why are the properties in fine-grained materials uniform in different directions?
c) What are anisotropic materials?
d) How can you solve a problem that deals with plastics?
e) What initial forces are there in a body before loading?
f) What may happen to a body under load?
g) Which are he forces of elasticity?
h) What is he meaning of effect in the assumption 5?
i) With what bodies is the principle of superposition used?
j) Which principles permit the replacement of one system of forces by another?
II. Scan through the text and write a summary in Spanish.
Reading D: Ductility, brittleness and hardness
I. Before you start reading
I. Fill the blanks with words from the following list following the sentences.
I. a) What is ductility?
It is the ___________of a material to deform appreciably under a load before
____________.
List: tensile - rupture - ability
17
�I. b) What is brittleness?
It is the ___________to fail with very little______________.
List: deformation - tendency - ability
I. c) What is hardness?
It is the ability of a material to___________ wear or _____________.
List: tendency - penetration - resist
II. Can you predict what the title of the text will be?
Reading D: Ductility, brittleness and hardness
The ability of a material to acquire large permanent deformations without fracture is
known as ductility. The property of ductility is of prime importance in such processes as
extrusion, drawing, bending, etc. The measure of ductility is the percentage elongation d
at rupture. The greater d, the more ductile is the material. Highly ductile materials include
annealed copper, aluminium, brass, low-carbon steel, etc. Duralumin and bronze are
less ductile. Slightly ductile materials include many alloy steels.
A property opposite to ductility is brittleness, i.e., the ability of a material to fracture
without any appreciable permanent deformation. Materials possessing this property are
called brittle. For such materials, the amount of elongation at rupture does not exceed 2
to 5 percent, and in some cases it is expressed by a fraction of one per cent.
Brittle materials include cast iron, high-carbon tool steel, glass, brick, stone, etc. The
tension test diagram for brittle materials has no yield point or strain hardening zone.
There are materials that are capable of sustaining larger loads in tension than in
compression. These are generally materials having fibrous structure, such as wood and
various plastics. Some metals, such as magnesium, possess this property.
18
�The division of materials into ductile and brittle is purely conventional not only because
there is no sharp dividing line between them. Many brittle materials may behave as
ductile and ductile materials as brittle, depending on the conditions of testing.
The duration of loading and temperature have a very great affect on ductility and
brittleness. Under rapid loading, brittleness is displayed more sharply; while under
prolonged loading ductility is more pronounced. For example, brittle glass is capable of
developing permanent deformations under sustained loading at normal temperature.
Ductile materials, such as low-carbon steel, exhibit brittle properties under sudden impact
loading.
II. Begin reading
I. Read the text and draw out information related to the properties of these materials.
Follow the example.
Material
Annealed cooper
Cast iron
Duralumin
High – carbon tool steel
Glass
Bronze
Brick
Aluminium
Brass
Stone
Law - carbon steel
Property
Highly ductile
II. Scan through the text and find:
a) A connective indicating reason: ___________________________________________
b) Two sentences in passive voice: __________________________________________
c) The opposite of ductility: ________________________________________________
19
�d) A sentence expressing comparison: _______________________________________
e) Two modifiers and interpret them in Spanish: ________________________________
III. Find information to answer the following questions.
1. - What is the text about?
2.- What is ductility?
3. - What is brittleness?
4. - Explain with your own words when a material has brittleness properties.
5. - Mention some ductile materials.
III. Keep on reading
I. Pair work.
Student A: You are involved in a research project about Strength of Materials. You need
to select the materials taking into account their main characteristic.
Student B: You are going to help your partner to group the materials according to their
main characteristic.
- Act out the conversation.
II. Scan through the text again and write a summary in English.
Reading E: Beams-shear forces and bending moments
I. Before you start reading
What do you know about beams?
Organize the following chunks, so as to write:
20
�1. The definition of a beam.
2. Way in which a beam is generally categorized.
3. The tendency to the bending of a beam.
a) and it is called shear - to the bending of a beam In addition - to slip past the adjacent
section - there is a tendency of one section of a beam.
b) by bending elastically A beam - transverse loads and forces - is a member which
resists.
c) or statically indeterminate - They may be - as either statically determinate - generally
categorized.
Reading E: Beams-shear forces and bending moments
Source: Statics and Strength of Materials.
Milton G. Bassin and Stainly M. Brodsky
U.S.A. 1960
A beam is a member which resists transverse loads and forces by bending elastically.
They may be generally categorized as either statically determinate or statically
indeterminate.
When a simply supported beam is carrying a load, it produces a bending in the beam at
all points. Any sections such as AB and CD are rotated into new positions by the bending
of the beam. The length BD is shortened or compressed, and length AC is lengthened or
stretched. The resistance offered to this shortening and lengthening of the fibbers is
called internal fibber stress, or simply stress. The upper fibbers are in compression and
the lower ones in tension.
In addition to the bending of a beam, there is a tendency of one section of a beam to slip
past the adjacent section. This tendency is called shear, and shear forces must be
resisted by the fibbers of the beam. Shearing forces are parallel to the plane of the
section.
21
�It is useful to know what shear force a beam must resist at every section. The shear force
at any section of the beam is the algebraic sum of all forces acting on the beam to the left
of that section. This information is conveniently represented in a shear-force diagram
which is drawn in projection with the sketch of the beam in represents. The shear-force
diagram is a plot of the next external shearing forces which act at each beam cross
section. These forces are caused by the loading of the beam. The fibber of the beam
material must resist these forces to maintain static equilibrium.
II. Begin reading
I. Decide whether the following statements are True or False, by referring to the
information in the text. Then make the necessary changes so that false statements
become true:
1. A member which resists transverse loads and forces by bending elastically is called a
beam. ______
2. A load on a simple beam produces a bending at points. ______
3. The length BD is not shortened. ______
4. The resistance to shortening and lengthening of fibbers is known as external fibbers
stress. ______
5. The fibbers of the beam material must not resist the shearing forces to maintain static
equilibrium. ______
6. The designer must know how the bending changes at all points in the beam. _______
7. The algebraic sum of the moments at any section of a beam is called the bending
moment. __________
22
�II. Fill in the blanks with words from the reading.
1. The upper _________are in compression and the lower ones are in ___________
2. The load supported by a simple beam produces a ____________ on it at different
points.
3. The static equilibrium is maintained by the________ of the_________material which
must resist these forces.
III. Analyze and interpret in Spanish the following modifiers taken from the text
studied:
a) Transverse loads and forces
_________________________________________________________
b) Simply supported beam
_________________________________________________________
c) Internal fibber stress
________________________________________________________
d) Shear-force diagram
________________________________________________________
e) External shearing forces
________________________________________________________
III. Keep on reading
I. Pair work.
Student A: You are researching about the uses or functions of a beam because you have
a final test the day after tomorrow.
23
�Student B: You are helping your partner to study for the test and you already know the
uses or functions of a beam.
- Be ready to act out the conversation.
II. Scan through the text and then write a summary of the main ideas of the text in
English.
Theme 2: Machines
Reading A: Automatic Control of Machine Tools
I. Before you star reading
I. What do you know about automatic control?
- Organize the following chunks, so as to write:
1. The definition of automatic control.
2. The classification of the control.
3. Members of it.
a) In addition - irrespective of its purpose and action - any elementary automatic control
mechanism - includes three principal members:
1- The primary transducer
2- The intermediate transducer
3- The operative member
24
�b) to perform a specific operation - Any such mechanism designed - an elementary
automatic-control mechanism - may be called.
c) by means of command signals - into analogue and discrete signals - Automatic control
of machine tools - is accomplished - which are classified.
Reading A: Automatic Control of Machine Tools
Various control mechanisms are installed on machine tools to automate them. Any such
mechanism designed to perform a specific operation may be called an elementary
automatic-control mechanism. It may be a simple one when performing but one
operation, but a complex one when performing several operations. A simple mechanism,
for instance, may be used for engaging the feed movement, a complex mechanism- for
releasing, feeding and clamping the bar stock.
Automatic control of machine tools is accomplished by means of command signals,
which are classified into analogue and discrete signals. The discrete signal is sent
continuously, and there is a functional relation between the input and output values of
this signal. The discrete signal is sent periodically in the form of successive impulses,
their amplitude, duration and repetition rate depend on the input signal value only at
some moments of time.
Any elementary automatic control mechanism, irrespective of its purpose and action,
includes three principal members.
(Sometimes there is no second member)
4- The primary transducer
5- The intermediate transducer
6- The operative member
The above classification is general rather than comprehensive and does not cover the
various other arrangements of automatic machine tool control systems.
25
�II. Begin reading
I. Expand your vocabulary. Scan through the text and:
I. a) Find the English equivalent to:
a) llevar a cabo, realizar ____________________
b) avance__________________
c) liberando, aliviando___________________
d) pinzando _________________
e) engranaje___________________________
f) señal de entrada______________________
g) transductor__________________________
II. Scan through the text and find:
a) The opposite of few_______________
b) A sentence in passive voice_________________________________________
_________________________________________________________________
c) Two modifiers and interpret them in Spanish____________________________
_________________________________________________________________
_________________________________________________________________
26
�III. Scan through the text and fill in the blanks with the corresponding word.
1. Many control structures are located on equipment to ____________them.
2.
Classified
parts
of
automatic
control
mechanism
are
_____________and
_______________.
III. Keep on reading
I. Scan through the text and write a summary in English.
Reading B: A car wash for cleaner air
I. Before you start reading
Test your vocabulary. Match the words in Column A with their corresponding equivalent in
Column B.
Column A
Column B
1. Power source
__Vapor
2. Pump
__Bombear
3. Steam
__Alfarería
4. Crankshaft
__Fuente de energía
5. Pottery
__Cigüeñal
Reading B: A car wash for cleaner air
Nitrogen oxides, carbon monoxide, particulates, hydrocarbons, lead you name it, the
internal- combustion engine ejects it out. And yet nobody has invented, or even come close
to inventing, a mobile power source as compact, powerful and useful as the internalcombustion engine. What can be done about its dangerous exhaust?
27
�In principle, the answer is simple let the engine burn its fuel completely. It would. Then
produce carbon dioxide and steam, and nothing else. The trouble is that any flame in a
closed cylinder is inevitably quenched on the surrounding cold surfaces, gyring the
unpleasant products of incomplete combustion our engineers now have a solution.
Imagine, they say, a porous engine, with air being pumped continuously into the cylinder
through the walls. The air would sweep the flame back; it would never touch the walls, and
never be cooled on them. But how to lubricate such an engine
Oil would block the pores, and act as a quenching surface for the flame. At first, our
engineers thought of using the incoming air itself as a lubricant.
Bearing in which compressed air emerges from a group of small holes, are used in many
scientific instruments. But air is too mobile and compressible to lubricate the violently hitting
pistons and crankshaft of a car engine. So our engineers will bravely lubricate their porous
engine not with air, but with water.
Water is usually a bad lubricant it runs away too easily. But if you pump it continuously into
position through porous surfaces, then it should be useful. Even better, abandon the radiator
and let the engine run hot. The water will then boil as it emerges, pressurising itself with
expanding steam. And porous cylinder walls which save off steam will give even cleaner
combustion than air would do, the steam will «crack» any incompletely burnt fuel. It may
even give a bit more power finally, for a change, our engineers want to make though porous
parts of their engine from ceramics although concrete and pottery are porous, they seem
unpromising engineering materials. But advanced ceramics are a tough proposition these
days turbines are made of them, and an uncooled ceramics diesel engine has already been
tested for military use.
When perfected, the new «Wet Cement» engine (as dread co engineers have called it will
dean up your car dramatically. You will have to fill up with water as well as petrol at every
stop in return you will get a guaranteed clean exhaust, no dirty polluting oil, and no radiator
to boil, freeze or crack. Motoring correspondents will love it too it will give them yet another
chance to revive that old dream about «a car that runs on water».
28
�II. Begin reading
I. Scan through and find synonyms for the following words
a Energy: _________________
b Vapour: _________________
c Cooled: _________________
d Contact: ________________
e Holes: _________________
II. Scan through the text again and find:
a Two possessive adjectives: ____________________________________________
b Two personal pronouns: _______________________________________________
c Two connectives and state their functions: _________________________________
dTwo sentences in passive them: _________________________________________
III. Scan through the text again and say if these sentences are True or False.
a Ceramics have never been used in an engine before._____
b Water is always a bad lubricant in the porous engine described in the text._____
c The author of the text considers the internal-combustion engine as a positive
invention in general.______
d The only innovation of the new engine is the porous surface of its walls._______
e If air were used instead of water, the engine would be more powerful._________
f) Do Dreadco’s engineers think that motoring correspondents will like the idea? ______
29
�III. Keep on reading
I. Scan through the text to find the answers to these questions (You may be asked to talk
about this in the practice session with your classmates and your language professor).
a What are exhaust fumes composed of?
b Why can the new engine be uncomfortable for the user of the car?
c Why did they choose water, instead of air, as a lubricant?
d Why is the new engine called «Wet Cement engine»?
Reading C: Kinematics
I. Before you start reading
I. Fill in the blanks to complete these definitions using words from the list.
1.a) What is dynamics?
Dynamics is the __________ of the interaction of masses, ___________, and the
corresponding _______________.
a) motions
b) study
c) forces
1.b) What is the object of this study?
The object of this study is the development of the____________to write mathematical
_______________which describes these interactions, at least, to the ____________
required by the _____________ at hand.
a) accuracy
b) problem
c) capacity
d) expressions
30
�Reading C: Kinematics
From «Vector Mechanics for Engineers»
by Harry R. Nara
Dynamics is the study of interaction of masses, forces, and the corresponding motions.
The development of the capacity to write mathematical expressions which describe these
interactions, at least, to the accuracy required by the problem at hand, is the object of
this study. As with all attempts to describe nature through mathematical models,
simplifying assumptions must often be made, but the results may still be useful as long
as these results are confirmed by experiment to the accuracy demanded.
A few examples will illustrate this point. In some dynamics investigations it is common to
assume that the masses involved are rigid.
This statement is sufficiently accurate for many problems in dynamics, where the motions
of the bodies as a whole are large compared with their deformation and a useful result is
obtained by neglecting the deviations from perfect rigidity.
In the study of a vibrating beam, nevertheless, this assumption cannot be employed as
we are primarily concerned with the displacements of the particles which make up
the beam. Unless otherwise stated, the objects to be discussed are considered to be
rigid, i.e., the distance between any two points and the angle between any two lines
located in the body will be considered constant.
The concept of the mass point or particle is another simplifying assumption we will use in
formulating some problems. Although the mass of an object is distributed throughout its
bulk, under some circumstances satisfactory accuracy is achieved by regarding the
mass as concentrated at a point. This approximation is likely to be adequate,
particularly if the important length parameters describing the geometry of motion are
large compared with the dimensions of the object or if the object is subject to a pure
translation without rotation. The balancing of an automobile wheel is a slightly altered
example of this idea. The wheel radius which describes the motion of the true mass is
large, relative to the width of the tire, justifying the common assumption that the wheel
and the tire is a disk of negligible thickness. Balancing is normally performed by adding
weights in the plane of the disk and no distinction is made whether the weights are added
to the outside or inside the rim or to both.
31
�Two common types of problems arise in dynamics –the determination of the motion of a
body or bodies under the influence of a given set of forces, and conversely, the
determination of the forces required to impart prescribed motions to an object or a group
of objects. The flight of a rocket is an example of the first type of problem, since it is
often necessary to predict the flight path of the vehicle while under the influence of its
thrust force, the atmospheric resistance, control actions, and the force of gravity. The
second class of dynamics problems is met most often in the analysis of machinery
mechanisms, that is, the moving parts of a given machine. The geometric configuration of
a mechanism determines the motion of its elements while the forces which act on each
element are to be found so that they might be proportioned adequately to carry the
required loads.
In both situations, a precise means of defining motion is essential.
Therefore, the characteristics of motion and its specification, which is the study of
kinematics, will be considered prior to discussing the underlying principles of dynamics.
II. Begin reading
I. Scan through the text and find the synonyms of these words.
a) If, provided that: _________________
b) Girder, ray: _____________________
c) Supposition, principle: _____________
d) Exposed: _______________________
e) Emerge, rise: ____________________
II. Complete the following cooperative crossword puzzle. Work in pairs. In order to solve
this crossword puzzle, you will have to cooperate with your partner. You have only the
definitions and your partner has the puzzle. Read, and if necessary, explain the
definition when your partner asks. You may not look at the puzzle and your partner may
not look at the definitions. In other words, you may cooperate verbally but not visually!
32
�1
2
3
4
5
6
7
8
9
10
11
12
Across
3. Vice versa, with the alteration or order
changed. (paragraph 5)
5. Girder, a horizontal heavy strong member
that supports vertical loads; member on
which the weight of a floor is carried.
(paragraph 3)
6. Removals from the usual or proper place.
(paragraph 3)
7. To push or drive with force. (parag. 5)
11. That can be neglected. (paragraph 4)
Down
1. Unsuccessful efforts. (paragraph 1)
2. A synonym of however, but. (parag. 3)
4. Suppose. (paragraph 2)
8. Mass volume, an aggregate that forms a body
or unit, with reference to size or amount.
(paragraph 4)
9. The outer part of a wheel, border. (paragraph
4)
10. Principally, originally, at first. (parag. 3)
12. Included, implicated, implied. (parag. 2)
III. Scan through the text and fill in the blanks according to the reading selection:
1. Dynamics deal with the ______________ between masses, forces and motions.
2. _______________are usually necessary when an attempt to describe nature through
models is made.
3. In many cases it must be assumed that the masses are____________________.
4. A mass is assumed to be rigid when the deviations from the perfect rigidity
are_________________.
5. The mass of an object is distributed ________________its bulk and yet we must
sometimes regard it as concentrated at a __________________.
6. We add ________________ in the plane of the disk to perform balance.
33
�7. The flight of a rocket exemplifies the motion of a body under________________.
8. Atmospheric resistance interferes with ________________ of a vehicle.
9. To ______________machinery mechanisms is a common problem in dynamics.
10. The characteristics of _________________ is the main concern of kinematics.
IV. Cross out the word that does not belong to the group.
1. particle – fraction – fragment – point
2. rigid – static – mobile – intelligent
3. employ – use – utilize – state
4. between – through – and – among
5. therefore – thus – hence – nevertheless
6. angle – mass – bulk – body
7. length – gravity – width – thickness
8. accuracy – approximation – development – deviation
9. rotation – balancing motion – distance
10. consequently – on the contrary – vice versa – conversely
III. Keep on the reading
I. Scan through the text to find the answers to these questions (You may be asked to talk
about this in the practice session with your classmates and your language professor).
1. How can the result of simplifying assumptions be confirmed?
2. In which field is it usually assumed that the masses involved are rigid?
3. Why can we not assume that the masses involved in the study of a vibrating beam are
rigid?
4. In what way is the mass of an object actually distributed?
34
�5. Why is the concept of the mass point or particle used in formulating some problems?
6. How is the geometry of motion described?
7. How is the motion of the true mass described in the example of the automobile wheel?
8. Give and example of the determination of he forces required to impart prescribed
motions o a group of objects?
9. What determines the motions of a mechanism?
10. What does Kinematics study?
Reading D: The centre lathe
I. Before you start reading
I. Test your vocabulary. Match the words in Column A with their corresponding equivalent
in Column B.
Column A
Column B
1. Bed
____ Husillo
2. Headstock
____ Cabezal móvil
3. Spindle
____ Caja de velocidades
4. Tailstock
____ Bancada
5. Gearbox
____ Cabezal fijo
Reading D: The centre lathe
Source: Lathes. Houghton, Stephen Philip.
Vol. 1. London. 1963.
The centre lathe was the first and still is probably the most important machine tool in any
engineering establishment for it will develop a true cylinder. Broadly speaking the operations
performed upon the lathe may be classified under the following headings:
35
�(a) Turning, that is removing the material from the outside, or periphery of a component,
thus giving a circular cross-section.
(b) Facing, that is removing from the face of an article.
(c) Boring, the cutting away of surplus material from the interior of a work piece, and
producing a bore with a circular cross-section.
(d) The cutting of threads, both single and multi-start.
In addition there are several other machining operations which, with the necessary
equipment, extend the usefulness of a centre lathe, and in some instance make it a
special type. A few of these operations are: form turning or boring, drilling and tapping,
the form-relieving of milling cutters, tabs, and hobs, oval turning and boring, also
milling, grinding and tapping.
The main dimensions of a centre lathe are generally listed in the following manner:
a) The height of the centres measuring off the lathe bed.
b) The swing which is twice the height of the centres.
c) The maximum length that can be accommodated between the lathe centres.
Different types of lathes are:
1) The small bench lathe, having, say, 4 in centres.
2) The standard centres lathe of around 6 to 12 in centres, mounted upon legs and
having a tailstock.
3) The turning and facing lathe, the design of which omits the tailstock.
4) The gap lathe, which is often similar to 2 but has a gap so that large diameter work
can be handled.
36
�5) The relieving lathe as used in the production of milling cutters, taps and hobs.
6) Roll turning lathes, which in effect, are very large centre lathes, designed to machine
the large rolls as used in the steel and other mills.
The lathe bed is usually a cast-iron component of sufficient depth and width to ensure
strength and rigity, with freedom and distortion. The mass of metal should be arranged to
absorb all the vibrational stresses which may be created during the various machining
operations.
The headstock is the source of power. In addition to a motor, the headstock contains a
gearbox to adjust the speed of rotation.
There is a distinct cleavage between the old and the modern lathes. The old lathe had a
cone-pulley drive; where as the modern tendency is to arrange for an all-geared
headstock, having a single-pulley drive.
The spindle of the headstock, as filled to a modern-designed lathe, is usually large in
diameter in order to give rigity and of the hollow type so that bar material may be passed
through the bore. The spindle has a center for supporting one end of the work piece, the
spindle also causes the work piece to rotate. The main purpose of the spindle is holding
another centre which supports the other end of the work piece.
The choice of large diameter and well-placed bearings prevents «whipping» at high
speeds. At all times, speed changing should be done with care, and the maker’s
recommendations strictly followed. A safe practice is always to stop the machine for any
speed changing and it is essential that all tools are with drawn for the work piece prior to
stopping the machine.
37
�II. Begin reading
I. Scan through the text and fill in blanks with the corresponding word.
1. A lathe has two centers, one which usually moves while the other is stationary; they
are used to _____________the work piece.
2. There is a difference __________ between the old and the modern lathes.
3. A synonym of hold is ____________________.
4. A _______________is a machine used for performing operations on a part.
5. In a lathe the supporting surface or structure is called the _______________.
II. Scan through the text and try to organize these ideas in order of appearance in the
text.
a) ______ A lathe has three main dimensions.
b) ______ A lathe can perform different types of operations such as turning, facing,
boring and cutting of threads.
c) ______The bed is one of the principal parts of the lathe.
38
�d) ______There are many other machining operations that can be performed by a lathe.
e) The headstock constitutes the source of power and it contains a gearbox to adjust the
speed of rotation.
f) There are different types of lathes according to their functions.
g) For any speed changing it is advisable to stop the machine.
III. First unscramble the letters to make words. The clues or simple definitions will help
you.
KCOTSDAHE
ARGEXOB
CKOTSILTA
SDLEPIN
DEB
1. It contains the motor, gearbox and the spindle.
2. It adjusts speed of rotation.
3. It transmits rotational movement and holds center.
39
�4. It holds the head center
5. It supports all the principal parts.
Next use the circled letters to form another word
6. It is a machine used for performing operations on a part.
III. Keep on reading
I. Two students are talking about the class. If you complete this dialog you can know. Be
ready to act it out.
Eduard: I really liked the English lesson today.
Nora: Me too. Eduard, can you tell the ______________ types of _____________
a lathe can perform?
Eduard: It´s too easy. They are turning, _____________, boring and ____________
of thread.
Nora: That´s right. And what is one of the main parts of the lathe?
Eduard: Of course, it is the ____________. Nora, what is that constitute the source of
power?
Nora: The ____________, and it contains a _____________ to adjust the speed of
rotation.
II. Scan through the text and write a brief summary in English.
Theme 3: Thermodynamics
Reading A: Thermodynamics systems
I. Before you start reading
I. Fill in the blanks to complete these definitions using words from the boxes.
40
�a) What is a system?
1.a) It is the ____________ of the universe which is ____________for thermodynamic
________________.
chosen
consideration
portion
1.b) What does a system consist of?
It
____________consists
of
a
__________amount
(or
amounts)
of
a
___________substance (or substances).
specific
definite
usually
II. Can you predict what the title of the text will be?
Reading A: Thermodynamics systems
From «Thermodynamics for Chemists»
By S. Glasstone.
In order to develop the consequences of the laws of thermodynamics, it is necessary to
define the terms of reference.
The portion of the universe which is chosen for thermodynamic consideration is called a
System; it usually consists of a definite amount (or amounts) of a specific substance (or
substances).
A system may be homogeneous, that is, completely uniform throughout, such as a gas or
a mixture of gases, or a pure liquid or solid, or a liquid or solid solution. When a system is
not uniform throughout it is said to be heterogeneous; it then consists of two or more
phases which are separated from one another by definite bounding surfaces. Systems
consisting of a liquid and its vapor, or of two immiscible (or partially miscible) liquids, or
of two or more solids, which are not a homogeneous solid solution, are examples of
heterogeneous systems.
41
�A system may be separated from its surroundings, which consist of the remainder of the
universe, by a real or imaginary boundary through which energy may pass, either as
heat or as some form of work. The combination of a system and its surroundings is
sometimes referred to as an isolated system.
The thermodynamic or macroscopic state, or in brief, the state, of a system can be
defined completely by four observable properties or «variables of state» These are: the
composition, pressure, volume and temperature. If the system is homogeneous and
consists of a single substance, the composition is fixed, and hence, the state of the
system depends on the pressure, volume and temperature only. If these properties are
specified, all other physical properties, such as mass, density, viscosity, refractive index,
dielectric constant, etc., are there definitely fixed. The thermodynamic properties thus
serve to define a system completely.
In actual practice it is not necessary to state the pressure, the volume and the
temperature, for experiment has shown that these three properties of a simple
homogeneous system of a definite mass are related to one another. The value of any
one of these properties thus depends in the value of the other two. The relationship
between them is called an equation of state, but its precise form lies, «strictly
speaking», outside the province of pure thermodynamics; an equation of state must be
derived from molecular (kinetic) theory or from direct experiments on the system under
consideration.
Other equations of state, particularly those involving several empirical constants, are
determined from experimental data, although their general form may have a theoretical
basis. The derivation of such equations is not possible by means of thermodynamics, but
the results of thermodynamics may be applied to them with interesting consequences. In
general, the pressure, volume and temperature of a system are not independent
variables, and consequently the thermodynamic state of a simple homogeneous system
may be completely defined by specifying two of these properties.
The results stated above, namely, that only two of the three properties of a system, viz,
pressure, volume and temperature are independently variable, and that a homogeneous
system of definite mass and composition is completely defined by these two properties,
are based on the tacit assumption that the observable properties of the system are not
undergoing any change with time.
42
�Such a system is said to be in thermodynamic equilibrium. Actually, this term implies
three different types of equilibrium which must exist simultaneously. First, there must be
thermal equilibrium, so that the temperature is the same throughout the whole system.
Second, if the system consists of more than one substance there must be also chemical
equilibrium, so that the composition does not vary with time. Finally, the system must be
in a state of mechanical equilibrium; in other words, there must be no macroscopic
movements within the system itself, or of the system with respect to its surroundings.
Disregarding the effect of gravity, mechanical equilibrium implies a uniformity of
temperature and pressure throughout the system; if this were not the case, it would be
impossible to describe the system in terms of pressure, volume and temperature.
II. Begin reading
I. Try to find words related to the technical vocabulary studied in class. They can be in all
directions. Then complete the sentences.
S
U
R
R
O
U
N
D
I
N
G
P
T
A
H
M
S
T
D
N
S
V
C
X
H
Y
Z
I
L
M
N
X
O
W
H
O
E
P
Q
S
N
A
M
E
L
Y
O
T
R
M
A
C
B
C
D
F
A
G
S
S
E
Q
B
I
T
I
C
A
T
V
E
E
B
W
X
B
P
E
N
S
E
T
N
S
Y
D
R
L
I
E
T
N
D
S
R
A
M
F
R
E
M
A
I
D
E
R
P
H
R
E
L
A
T
I
O
N
S
H
I
P
R
Z
W
V
Y
V
W
Y
Z
M
S
T
B
A
S
S
U
M
P
T
I
O
N
D
1. Areas that is around something, vicinity.
2. Selected.
3. Homogeneous physically distinct portions of matter in system which is not
homogeneous.
43
�4. Rest.
5. Separated from the rest.
6. Hence, thus, consequently.
7. Be or stay at rest in a horizontal position; be placed.
8. Connection, interrelation.
9. Not expressed.
10. That is to say, viz, videlicet.
11. Supposition.
II. Scan through the text and find:
a) Two connectives and state their functions: ____________________________
____________________________
b) Two sentences in passive voice: _____________________________________
_________________________________________________________________
_________________________________________________________________
c) Two conditional sentences: _________________________________________
_________________________________________________________________
_________________________________________________________________
d) A sentence in present perfect: _______________________________________
_________________________________________________________________
III. Scan through the text to find the answers to these questions (You may be asked to
44
�talk about this in the practice session with your classmates and your language professor).
1. How can a system be?
2. When is a system homogeneous?
3. When can we consider a system heterogeneous?
4. What is an isolated system?
5. How can we define the thermodynamics state of a simple homogeneous system?
6. When is a system in thermodynamic equilibrium?
9. What do we mean by thermal equilibrium?
10. What does mechanical equilibrium imply?
III. Keep on reading
I. Scan through the text and write a summary in Spanish.
Reading B: Thermodynamics reversibility
I. Before you start reading
I. Rate your vocabulary. Try to write the Spanish equivalent of these words:
a) Restore: _______________
b) Evolve: ________________
c) Gradients: ______________
d) Disturb: ________________
e) Take up: _______________
f) Stage: _________________
g) Absorption: _____________
h) External: _______________
45
�II. Look up the new words in a bilingual dictionary and write them down in your notebook.
Reading B: Thermodynamics reversibility.
From «Thermodynamics for Chemists»
By S. Glasstone.
A particular type of path between two thermodynamic states is of special interest. This is
the kind of path for which it is postulated that all changes occurring in any part pf the
process has been performed and then reverse, both the system and its surroundings
must be restored exactly to their original state. A process of this kind is said to be
thermodynamically reversible. In general, in order to follow a reversible path, it is
necessary that the system should always be in a state of virtual equilibrium, and this
requires that the process be carried out infinitesimally slowly.
A simple illustration of a reversible process is provided by isothermal evaporation
carried out in the following manner. Imagine a liquid in equilibrium with its vapor in a
cylinder closed by frictionless piston, and placed in a constant temperature bath, i.e., a
large thermostat. If the external pressure on the piston is increased by a infinitesimally
small amount, the vapor will condense, but the condensation will occur so slowly that the
heat evolved, i.e., the latent heat, will be taken up by the thermostat.
The temperature of the system will not rise, and the pressure above the liquid will remain
constant. Although condensation of the vapor is taking place, the system at every instant
is in a state of virtual thermodynamic equilibrium. Similarly, if the external pressure is
made just smaller than the vapor pressure, the liquid will vaporize extremely slowly, and
again the temperature and pressure will remain constant. The system is changing, since
vaporization is taking place, but the process may be regarded as a series of
thermodynamic equilibrium states. Rapid evaporation or condensation, by the sudden
decrease or increase of the external pressure, will lead to temperature and pressure
gradients within the system, and thermodynamic equilibrium will be disturbed.
Processes of this kind are not thermodynamically reversible.
The isothermal expansion of a gas can be carried out reversibly by placing the cylinder of
gas in thermostat, as described above, and adjusting the external pressure so as to be
less than the pressure of the gas by infinitesimally small amount. As the gas expands,
46
�however, its own pressure decreases, since the temperature is maintained constant.
Hence, if the process is to be thermodynamically reversible, it must be supposed that the
external pressure is continuously adjusted so as to be always infinitesimally less than the
pressure of the gas. The expansion will then take place extremely slowly, so that the
system is always in virtual thermodynamic equilibrium. The heat required by the gas, to
balance the energy expended in the form of the work against the external pressure, is
taken up from the thermostat, but since the process is carried out extremely slowly, the
absorption of energy as heat keeps pace with the loss as a work, and the temperature of
the system remains constant. If at any instant during expansion, the external pressure is
adjusted so that it is maintaining just infinitesimally greater than the gas pressure, the
process will be reversed, and the gas will be compressed. At every stage in the
compression the system and surroundings will be, apart from infinitesimal differences, in
exactly the same thermodynamic state as they were at the corresponding point in the
expansion.
If the expansion were carried out rapidly, e.g., by sudden and large increase of the
external pressure, the processes would not be reversible. The changes would not involve
a continuous succession of equilibrium states of the system, and hence they could not be
reversible, there would be both temperature and pressure which would be different in the
expansion and compression; the conditions for a thermodynamically reversible process
would thus not be applicable.
The discussion given above has referred in particular to isothermal changes; but
reversible processes are not necessarily restricted to those taking place at constant
temperature. A reversible path may involve a change of temperature as well as of
pressure and volume.
It is necessary; however, that the process should take place in such a manner that the
system is always in virtual thermodynamics equilibrium. If the system is homogeneous
and has a constant composition, two thermodynamics variables, e.g., pressure and
volume, will completely describe its state at any point in a reversible process.
47
�II. Begin reading
I. Read the text and draw out information related to:
The
definition
of
thermodynamically
reversibility process
Kind of process isothermal evaporation
produces
What rapid evaporation or condensation
provokes
II. Match the words in Column A with their corresponding equivalent in Column B.
Column A
Column B
1. expend
4. gradients
___ being in essence or effect but
not
in fact.
___to
put
back
into
its
original
state
___the rate of regular ascent or
descent.
___to consume by use.
5. restore
___ rate of movement.
2. pace
3. virtual
___ to remove by pulling.
___marked
by
changes
of
volume
under
conditions
of
constant
temperature.
III. Keep on reading
III. Scan through the text to find the answers to these questions (You may be asked to
48
�talk about this in the practice session with your classmates and your language professor).
1. What is necessary to follow a reversible path?
2. What happens when the internal pressure on the piston is augmented by an
infinitesimally small quantity?
3. How is the system when condensation of vapor is taking place?
4. What happens if the external pressure is made just smaller than the vapor pressure?
5. How can isothermal expansion be carried out reversibly?
6. What will make the process be reversed during the expansion?
7. When wouldn´t the process be reversible?
8. Why are reversible processes no necessarily restricted to those that place at constant
temperature?
9. What happens if the system is homogeneous and has a constant composition?
Reading C: The subject of Hydraulics
I. Before you star reading
I. Rate your knowledge of key vocabulary on this topic. Write an (X) next to the words you
can give their Spanish equivalents. Notice the grammatical category (part of speech) in
parentheses beside each word in the list. x
___covering (n)
___provides (v)
___equilibrium (n)
___globules (n)
___concern (v) (n)
___investigate (v)
___flow (n)
___mains (n)
___channels (n)
___hydromechanics (
___external (a)
___range (n)
___velocity (n)
___designing (n)
49
�II. Look up the new words in a bilingual dictionary and write them down in your notebook.
III. Fill in the blanks with the corresponding word from the previous list.
a) Hydraulics ____________ the methods of calculating and _____________ a wide
___________ of hydraulic structures.
IV. Read the list of words provided again. Taking into account their meanings and
relationships, can you predict what the title of the text will be?
Reading C: The subject of Hydraulics
From «Hydraulics» by Nekrasov
The branch of mechanisms which studies the equilibrium and motion of liquids and gases
and the force interactions between them and bodies through or around which they flow is
called hydromechanics or fluid mechanics. Hydraulics is an applied division of fluid
mechanics covering a specific range of engineering problems and methods of their
solution.
The principal concern of hydraulics is fluid flow constrained by surrounding surfaces,
i.e., flow in open and closed channels and conduits, as well as pipes, nozzles and
hydraulic machine elements.
Thus, hydraulics is chiefly with the internal flow of fluids. Likewise, it investigates what
might be called «internal» problems as distinct from «external»
problems involving the
flow of a continuous medium about submerged bodies, as in the case of solid body
moving in water or in the air. These «external» problems are treated in hydrodynamics
and aerodynamics in connection with aircraft and ship design.
It should be noted that the term «fluid», as employed in hydromechanics, has a broader
meaning than generally implied in everyday life and includes all materials capable of an
infinite change of shape under the action of the smallest external forces.
The difference between a liquid and a gas is that the former tends to gather in globules if
taken in small quantities and makes a free surface in larger volumes. An important
property of liquids is that pressure or temperature changes have practically no effect on
their volume, i.e., for all practical purposes they can be regarded as incompressible.
50
�Gases, on the other hand; contract readily under pressure and expand infinitely in the
absence of pressure, i.e., they are highly compressible.
Despite this difference, however, under certain conditions, the laws of motion of liquids
and gases are practically identical.
One such condition is low velocity of the gas flow as compared with the speed of sound
through gas.
Hydraulics concerns itself mainly with the motion of liquids.
The internal flow of gases is studied only in so far as the velocity of flow is much less
than that of sound and, consequently, their compressibility can be disregarded. Such
cases are frequently encountered in engineering, as for example, in the flow of air in
ventilation systems and in gas mains.
Investigations of the flow liquids, and even more so, of gases, is a much more difficult
task than studying the motion of rigid bodies. In rigid – body mechanics, one deals with
systems of rigidly connected particles in constant relative motion.
Fluid mechanics as a science has developed along two different paths. The first was the
purely theoretical one of precise mathematical analysis based on the laws of mechanics.
It led to the emergence of theoretical hydromechanics, which for a long time existed as
an independent science. Its methods provided an attractive and effective means of
scientific research. Nevertheless, a theoretical analysis of fluid motion encounters many
stumbling blocks, besides, it does not always answer the question in real situations.
Practice soon gave rise to a new science of fluid motion, hydraulics, in which the second
path was taken, that of extensive experimenting and accumulation of factual data for
application to engineering problem. In theoretical hydromechanics experiments are
widely used to verify the validity of its conclusions. Thus, the difference in the methods
employed is gradually disappearing.
The method of investigation today is as follows. The phenomenon is first simplified and
idealized and the laws of the theoretical mechanics are applied. The results are then
compared with experimental data, the discrepancies are established and the formulas
and solutions adjusted so as to make them suitable for practical application.
51
�Hydraulics provides the methods of calculating and designing a wide range of machinery,
such as: pumps, turbines, fluid couplings; and other widely used devices for machinetool design, foundry practice, the manufacture of plastics, etc.
II. Begin reading
I. Read the text and draw out information related to:
The definition of hydraulics as a special
subject.
The main concern of hydraulics.
Similarities between liquids and gases.
Differences between liquids and gases.
II. Organize the following ideas in order of appearance in the text:
a) «Internal» and «external» problems. ______
b) Advantages and disadvantages of a new science. _____
c) The meaning of fluid. ______
d) Problems that hydraulics solves. ______
e) Hydraulics as a special subject. _______
52
�III. Scan through the text and find:
a) Two sentences with connectives of addition:
_______________________________________________________________________
____________________________________________________________________
b) A sentence with a connective of contrast:
_______________________________________________________________________
____________________________________________________________________
c) A sentence with a connective of reason:
_______________________________________________________________________
____________________________________________________________________
d) Two sentences with connectives of consequence:
_______________________________________________________________________
____________________________________________________________________
III. Keep on reading
I. Scan through the text to find the answers to these questions (You may be asked to
talk about this in the practice session with your classmates and your language
professor).
1. What does fluid mechanics study?
2. What type of flow concerns hydraulics?
3. What type of problem does hydraulics study?
4. What do we understand by «fluids» in hydromechanics?
II. Scan through the text and write a summary in English.
53
�Theme 4: Cavitations
Reading A: Cavitations
I. Before you start reading
I. Test your vocabulary. Match the words in Column A with their corresponding equivalent
in Column B.
Column A
Column B
1. Motion
____garganta
2. Narrowing
____chorro, reacción
3. Throat
____estrechamiento
4. Pitting
____hoyo, foso
5. Jet
____movimiento
Reading A: Cavitations
Textually from «Hydraulics» by B. Nekrasov.
In some cases of fluid motion in closed conduits, there takes place a phenomenon which
is due to a change in the physical state of a liquid: vaporization and evolution of gases
dissolved in it.
When a liquid flows through a narrowing in a pipe its velocity increases and the pressure
intensity diminishes. If the absolute pressure drops to the vapor pressure of the liquid for
the given temperature, evaporation commences and gases evolve. In short, the liquid
simply begins to boil locally. When the stream diverges after the throat – like narrowing,
the velocity drops, the pressure increases and the boiling stops; the vapor then
condenses partially or completely and the gases redissolve.
This local boiling of a flowing liquid is known as cavitation.
A simple device enables the phenomenon to be observed visually.
54
�Water or some other liquid is brought under pressure to a valve, through which it flows
into a glass tube with a venturi contraction.
When the valve is opened slightly the discharge is small, the velocity of the stream is
low, the pressure drop at the throat of the tube is small, and the stream is transparent:
no cavitation takes place. The wider the valve is opened, the faster the velocity of the
stream and the lower the pressure in the narrowing.
Cavitation announces itself by characteristic noise and vibrations.
Prolonged cavitation has an erotive effect on metal walls. The reason for this is that
condensation of the bubbles of vapor takes place very rapidly and the cavities collapse
abruptly with high compressive stresses due to local water – hammer effects. The
pitting of walls occurs not at the point where the vapor pockets appear but where they
collapse.
Fig. 1 Venturi tube for demonstrating Cavitation.
Cavitation thus has an adverse effect on pipelines and hydraulic systems. When
cavitation develops the resistance of pipes increases sharply, with a corresponding
reduction in discharge.
Cavitation may develop in any local narrowing followed by expansions, such as faucets,
valves, gates orifices and jets.
55
�In some cases cavitation may also develop when a narrowing is not followed by a
diverging section and in straight pipes when the elevation head or energy losses
increase.
Cavitation may occur in hydraulic machines such as pumps or turbines, and on the
blades of rapidly revolving ship propeller screws.
In these cases the result is a sharp decline in the efficiency of a machine and a gradual
wearing of its parts.
In aircraft hydraulic systems, cavitation may occur because of a reduced barometric
pressure with height. In this case the cavitation zone extends over a considerable
portion of the low-pressure pipelines (suction pipes) and even along the whole length.
When this happens the stream in the pipe divides into a liquid and vapor phase.
(a)
(c)
(b)
(d)
Fig. 2 Vapourisation in Low- Pressure Pipes.
In the initial stage the vapor phase appears as minute bubbles spread evenly along the
flow. As vaporization continues and the amount of vapor increases, the bubbles grow
larger and drift along the upper surface of the pipe. Finally, the liquids and the vapor
phases may separate completely into two streams. In thin pipes, vapor locks may form
and the two phases move in intermittent columns.
56
�It is evident that the greater the vapor phase, the less the discharge through a pipe.
Condensation (partial or complete) of the vapor takes place in the pump of a system,
where pressure increases sharply or in the pressure pipe through which the liquid is
pumped to the consumer.
Cavitation phenomena are different in plain (simple) and component (complex) liquids. In
a plain liquid the pressure at which cavitation occurs corresponds to the saturation vapor
pressure, which depends only on temperature.
A component liquid consists of so-called light and heavy fractions.
The lighter fractions have a higher vapor pressure and they start boiling before the heavy
ones.
Condensation takes place in the reverse order.
Multicomponent liquids containin light fractions are more subject to cavitation and the
vapor phase persists longer, but the process is not so pronounced as in plain liquids.
II. Begin reading
I. Synonyms: From this list, choose a synonym for the word in bold type in each
sentence. Use appropriate tenses for verbs and singular or plural forms for nouns. You
can use the dictionary.
1. The velocity of a liquid increases and he pressure decreases when it flows through
narrowing in a tube.
2. Vaporisation of gases dissolved in water sometimes occurs in closed conduits.
3. If the absolute pressure drops o the vapor pressure of the liquid for the given
temperature, evaporisation starts and gases evolve.
4. The hole of walls does not happen at the place where vapour pockets appear.
5. The enlarged velocity diminishes again once the streamdiverges after the narrowing.
II. Scan through the text to find the answers to these questions (You may be asked to talk
57
�about this in the practice session with your classmates and your language professor).
1. What affects the velocity and pressure of a liquid in a closed conduit?
2. What produces cavitation?
3. When does evaporation begin?
4. When does a liquid flowing through a narrowing begin to boil, and when does it stop?
5. What does cavitation do to metals?
6. Give examples where cavitation may happen.
III. Keep on reading
I. Two students are talking about the topic of the lesson. If you complete this dialog you
can know. Be ready to act it out.
Jimmy: Johnny, I´m in doubt. Can you help with this topic?
Johnny: Of course, yes, what´s the problem?
Jimmy: What is the phenomenon of a local boiling of a liquid called?
Johnny: It is called ______________.
Jimmy: What affect the velocity and pressure of a liquid in a closed conduit?
Johnny: A narrowing in a _____________.
Jimmy: What does cavitation do to metals?
Johnny: It has an ____________effect on metal walls.
Jimmy: What favors cavitation?
Johnny: It is the easiest question of all. It may develop in any local _____________
followed by expansions, such as faucets, valves, ___________, orifices and
___________.
Jimmy: Than you brother. Now I really understand.
List:
erosive
jets
cavitation
58
�gates
narrowing
pipe
Complementary Texts
Reading A: Historical perspective of materials
Materials are probably more deep-seated in our culture than most of us realize.
Transportation, housing, clothing, communication, recreation, and food production
virtually every segment of our everyday lives is influenced to one degree or another by
materials. Historically, the development and advancement of societies have been
intimately tied to the members’ ability to produce and manipulate materials to fill their
needs. In fact, early civilizations have been designated by the level of materials
development (i.e., Stone Age, Bronze Age).
The earliest humans had access to only a very limited number of materials, those that
occur naturally: stone, wood, clay, skins, and so on. With time they discovered
techniques for producing materials that had properties superior to those of the natural
ones; these new materials included pottery and various metals. Furthermore, it was
discovered that the properties of materials could be altered by heat treatments and by the
addition of the substances. At this point, materials utilization was totally a selection
process, that is, deciding from a given, rather limited set of materials the one that was
best suited for an application by virtue of its characteristics. At was not until relatively
recent times that scientists came to understand the relationships between the structural
elements of materials and thief properties. This knowledge acquired in the past 60 years
or so, has empowered them to fashion, to a large degree, the characteristics of materials.
Thus, tens of thousands of different materials have evolved with rather specialized
characteristics that meet the needs of our modern and complex society; these include
metals, plastic, glasses, and fibbers.
The development of many technologies that make our existence so comfortable has
been intimately associated with the accessibility of suitable materials sometimes, «made
to measure». Advancement in the understanding of material type is often the forerunner
59
�to the stepwise progression of a technology. For example, automobiles, planes and
spaceships would not have been possible without the availability of inexpensive steel or
some other comparable substitute. In our contemporary era, sophisticated electronic
devices rely on components that are made from what are called semi conducting
materials. Nowadays there is an important growing of different kind of materials like
composites, biomaterials and nanomaterials.
Reading B: Some criteria to select the appropriate material
Why do we study materials? Many an applied scientist or engineer, whether mechanical,
civil, chemical or electrical, will at one time or another be exposed to a design problem
involving materials. Examples might include a transmission gear, the superstructure for a
building, an oil refinery component, or an integrated circuit chip. Of course, materials
scientist and engineers are specialists who are totally involved in the investigation and
design of materials.
Many times, a material is one of selecting the right material from the many thousands
that are available. There are several criteria on which the final decision is normally
based. First of all, the in-service conditions must be characterized, for this will dictate the
properties required of the material. On only rare occasions does a material possess the
maximum or ideal combination of properties? Thus it may be necessary to trade off one
characteristic for another. The classic example involves strength and ductility; normally, a
material having a high strength will have only a limited ductility. In such cases a
reasonable compromise between two or more properties may be necessary.
A second selection consideration is any deterioration of material properties that may
occur during service operation. For example, significant reductions in mechanical
strength may result from exposure to elevated temperatures or corrosive environments.
Finally, probably the overriding consideration is that of economics: what will the finished
product cost? A material may be found that has the ideal set of properties but is
prohibitively expensive. Here again, some compromise is inevitable.
The cost of a finished piece also includes any expense incurred during fabrication to
produce the desired shape.
60
�The more familiar an engineer or scientist is with the various characteristics and
structure- property relationships, as well as processing techniques of materials, the more
proficient and confident he or she will be to make judicious materials choices based on
these criteria.
61
�GLOSSARY:
- Accomplish: realizar, confirmar, llevar a cabo
-Alloy: alear, ligar, aleación
-Annealed copper: cobre recocido, cobre templado
-As a whole: as a unit, in general (en conjunto, como un todo)
-Assume: suponer, presuponer
-At least: at the mínimum; in any case (al menos, a lo menos, por lo menos)
-Attain: alcanzar, lograr
-Attempts: unsuccessful efforts (esfuerzo, empeño)
-Axis: eje
-Beam: girder, a horizontal heavy strong member that supports vertical loads; member on
which the weight of a floor is carried (viga, traba)
-Bed: supports all the principal parts (bancada)
-Behaviour: conducta, comportamiento, funcionamiento
-Bending: curvadura, flexión, torción
-Blade: asp; one of the parts of a propeller (hoja, cuchilla)
-Besides: also, in addition, even more so (además)
-Block: bloque
-Boil: hervor, ebullición, bullir, hervir
-Borne in mind: kept in mind; considered (mantener en mente, tener en cuenta,
memorizar)
-Bound: to form the boundary of; to limit (atado, ligado)
-Boundary: that which indicates or fixes a limit or extent (límite, frontera, término)
-Bounding surface: surface that limits or confines (superficie que limita)
-Brass: latón, cobre
-Brick: ladrillo
-Brittle: quebradizo, frágil
62
�-Bubble: a small body of air or gas within a liquid (burbuja, ampolla)
-Bulk: mass volume, an aggregate that forms a body or unit, with reference to size or
amount (bulto, volumen, grueso)
-Burn: quemadura, quemar
-Cast iron: de hierro colado, de fundición
-Centroids: successive centers in a rod (centro de gravedad)
-Channel: passage for water, canal (canal, conducto)
-Chiefly: mainly, principally (principalmente, mayormente)
-Chosen: selected (escoger, elegir)
-Clamp: pinza, tenaza, collar
-Concern: asunto, atañer, concernir, interesar
-Conduit: channel or pipe for carrying liquids through distances (tubo aislante)
-Constrained: confined, forced (constreñir, detener, encerrar, restringir)
-Constraints: forces acting upon a body (restricciones)
-Conversely: vice versa, with the alternation or order changed (contrariamente)
-Coupling: device that serves to connect the ends of adjacent parts (acoplamiento)
-Covering: including (cubierta, envoltura)
-Crack: hendidura, grieta, crujido, estallido
-Crankshaft: cigüeñal
-Cross-sectional: corte transversal
-Cumbersome: embarazoso
-Dam: a barrier to prevent the flow of water, as a bank or wall (presa, represa)
-Despite: in spite of; notwithstanding (a pesar de, a despecho de)
-Discharge: emission (descarga, desempeño, liberación, derrame)
-Displacements: removals from the usual or proper place (desplazamientos)
-Disturb: to interrupt or alter the normal condition (disturbar, incomodar, perturbar,
molestar)
63
�-Disk or disc: thin circular object or part; also a phonograph (disco)
-Drift along: to float or drive along by water or air (deriva)
-Drops: pendientes, descenso, lanzamiento
-Ductility: ductilidad
-Due to: as a result of; owing to (debido a)
-Elevation head: (Hydraulics): pressure of water (Carga)
-Elongation: alargamiento
-Encounter: meet, find (encontrar)
-Engaging: engranaje
-Evenly: uniformly (uniformemente)
-Even: (liso, llano)
-Evolve: to exhibit or produce by evolution (desarrollar, evolucionar)
-Expend: to consume by use (gastar, consumir)
-Extent: extensión, punto
-Factual data: data based on facts (datos, información precisa)
-Faucet: the terminal ending of a pipe system that permits the outlet of water; water tap
(cegrifo)
-Feed: alimentar, avanzar
-Fine-grained: having little fine lines and markings (de granulación fina, de fibra
compacta
-Flame: llama, flamear
-Flat: smooth and level; even (plano, llano)
-Flight: act of flying or passing through the air or outer space (tramo, arranque, vuelo)
-Flume: a large, inclined channel, trough or chute for conveying water
-Foundry: a place where founding takes place (fundición)
-Freeze: helar, congelar
-Gage: (espesor)
64
�-Gate: valve or door that permits or stops the passage of flowing water or liquid
(compuerta)
-Gearbox: adjust speed of rotation (caja de velocidades)
-Give rise: subida, elevación, salida, dar origen
-Glass: vidrio, cristal
-Globule: tiny or very small drop or ball (glóbulo)
-Gradients: the rate of regular or graded ascent or descent in temperature or pressure
(pendiente, gradiente, declividad)
-Gravel: loose rounded fragments of rock (grava, cascajo)
-Hardening zone: zona de endurecimiento
-Headstock: contains the motor (cabezal fijo)
-Height: the condition of being high (altura)
-Henceforth: from this time forward; therefore (de aquí en adelante)
-High-carbon tool: herramienta de acero de alto contenido de carbono
-Hitting pistons: pistones de empuje
-Horse-power type: / tipo de caballo de fuerza
-In short: briefly; by way of summary (en breve)
-In so far as: to such extent or degree as (en cuanto)
-Input signal: señal de entrada
-In brief: in short, briefly (en breve, brevemente)
-Involve: include, implicate, and imply (envolver, comprometer)
-Isolated: separated from the rest (aislado)
-Isothermal: of, relating to, or marked by changes of volumen or pressure under
conditions of constant temperature (isotérmico)
-Jet: stream of water that spurts or comes out suddenly with force (chorro, reacción)
-Knot: a hard mass of wood formed where a branch grows out from a tree, which shows
as a roundish, cross-grained piece in a board (nudo)
65
�-Lead: avance, adelanto
-Level out: to make equal or uniform (nivelar)
-Libounding surfaces: superficie que limita o restringe
-Lie: be or stay at rest in a horizontal position; be placed (configuración, lugar, posición,
sitio, ubicación)
-Likewise: also, moreover, too (igualmente, así mismo, además)
-Loads: cargas
-Low-carbon steel: acero de bajo carbono
-Main: a large pipe of water, gas, etc. (canalización eléctrica, red de consumo, conducto)
-Miscible: that can be fixed or combined (es relativo a sustancias totalmente soluble)
-Namely: that is to say, viz, videlicet
-Motion: movimiento
-Narrowing: part or place that is narrow; opposite to broad, wide (estrechamiento)
-Negligible: that can be neglected (insignificante, imperceptible)
-Nevertheless: however, but (sin embargo, no obstante)
-Noise: ruido, divulgar
-Nozzles: a projecting tube from which water is discharged, usually used at the end of a
hose or tube (tobera, tubo de salida)
-Outside the province of: outside the field or sphere of (fuera de provincial)
-Pace: rate of movement, growth or development (paso)
-Particularly: especially (particularmente, difícilmente, exigentemente)
-Phases: fases, poner en fase, llevar a cabo a etapas uniformes
-Phenomenon (sing.): phenomena (plural): any observable fact of scientific interest
(fenómeno)
-Pitting: from pit; hole, cavity (hoyo, foso)
-Plate: body limited by even surfaces (placa, lamina)
-Pliable: flexible, ductil
66
�-Pockets: small cavity (bolsa, depósito, bolso)
-Polluting oil: aceite contaminante
-Pottery: alfarería
-Power source: fuente de energía
-Primarily: principally, originally, at first (preliminarmente, principalmente, primeramente,
originalmente)
-Prior to: before (antes de)
-Pronounced: strongly marked (pronunciar)
-Pump: bomba
-Quench: apagar, extinguir
-Range: distance between certain limits; extend. Also, rank, class
-Readily: quickly; easily (de buena gana, fácilmente)
-Relationship: connection, interrelation (relación, conexión, interrelación)
-Releasing: liberando, aliviando
-Reliable: confiable, fidedigno
-Remainder: rest (resto, residuo)
-Restore: to bring back to or put back into a former or original state (restaurar, devolver)
-Rim: the outer part of a wheel, border (llanta, aro)
-Rod: varilla, vara
-Rugged: reforzado
-Setting: the process of hardening of concrete (fraguado, engaste)
-Sharply: acutely; impetuously; strongly (agudamente, afiladamente, puntiagudamente)
-Shell: body whose surfaces are curve (cilindro)
-Shearing: (deslizamiento)
-Shorted conductor: conductor en corto circuito
-Slender: long and thin (escaso, insuficiente)
67
�-Slightly: opposite of strongly (delgado, leve, pequeño, escaso)
-Slip: (deslizarse)
-So-called: called or designated in this way; commonly named or called (tan llamado)
-Surrounding: areas that is around something, vicinity
-Specimen: one of a group or class taken to show what the others are like; kind
(espécimen, muestra, tipo, sujeto)
-Spindle: holds the dead center
-Squirrel cage: jaula de ardilla
-Stage: step; a period in a process, activity or development (fase, etapa)
-Steam: vapor, vaho, humo
-Steel: acero, acerado
-Stiffness: rigidez
-Stone: piedra
-Straight-line axis: ejes rectilíneos
-Strain: (tensión, torcedura)
-Streama course of flowing water, current (vapor)
-Strength: (fuerza, resistencia)
-Stress: force; influence (esfuerzo)
-Strictly speaking: speaking with exactness, rigorously (hablando estrictamente)
-Stumbling blocks: an impediment to belief or understanding; an obstacle (escollo,
tropezadero)
-Sweep: reja excavadora, carrera (pieza de máquina), lira (tornos), desviación vertical
de laminación.
-Tacit: not expressed (tácito)
-Tailstock: transmits rotational movement and holds center (cabezal móvil)
-Take up: pick up, to remove by lifting or pulling (subir, levantar, emprender, obrar,
pegar)
68
�-Tension test diagram: diagrama convencional del ensayo a la tracción, donde se plotean
los valores de las deformaciones obtenidas a partir de la aplicación de esfuerzos de
tracción.
-Throat: garganta
-Thrust: to push or drive with force (empuje)
-Thereby: hence, thus, consequently (así, consecuentemente)
-Timber: madera de construcción
-To collapse: to fall or break down abruptly; disintegrate (desplome, fracaso, colapso)
-To a very small extend: to a very small degree; very little
-Transducer: transductor (estos son aparatos que convierten señales eléctricas en
mecánicas y viceversa)
-Turn on: encender
-Vapor locks: Sp. trampas de vapor, tapón de vapor
-Venturi: a short tuve inserted in pipeline used for measuring the quantity of a fluid
flowing (tubo de venturi: es un dispositivo creado por el científico del mismo nombre que
consiste en un estrechamiento y un ensanchamiento gradual del cauce para estudiar los
efectos de las variaciones de velocidad y presión en los flujos por tuberías).
-Virtual: being in essence or effect but no in fact (virtual, efectivo, eficaz)
-Virtually: adverb from virtual meaning being in essence or effect, but no in fact;
practically (eficazmente, virtualmente, efectivamente)
-Water- hammer effect: Sp. efecto de golpe de agua o de ariete
-Wearing: deterioration by use (desgaste, deterioro)
-Weir: a dam in a stream to divert its flow
-Yield: producción, rendimiento, cesión, límite
69
�HIGHER INSTITUTE OF MINING AND METALLURGY OF MOA
READING SELECTIONS FOR MECHANICAL ENGINEERING STUDENTS
ENGLISH IV
AUTHORS: M. sC. MIRTHA ODALIS OLIVERO HERRERA
M. sC. GEORGINA AGUILERA SABORIT
M. sC. ADIS FIOL CUENCA
M. sC. ADELFA VERDECIA CRUZ
M. sC. MARIO ANDRÉS NAVARRO CONSUEGRA
Lic. RICHEL FERNÁNDEZ MORA
Lic. YANISEL BATISTA NUÑEZ
Lic. ALIUSKA HINOJOSA CALA
�Página legal
Título de la obra: Reading selections for Mechanical Engineering students. English IV,
69 pp. Editorial Digital Universitaria de Moa, año 2018 -- ISBN: 978-959-16-4174-8
1. Autor: Mirtha Odalis Olivero Herrera
2. Institución: Instituto Superior Minero Metalúrgico «Dr. Antonio Núñez Jiménez»
Corrección: Dr. C. Tania Bess Reyes
Diseño: Wilkie Villalón Sánchez
Institución de los autores: ISMM «Dr. Antonio Núñez Jiménez»
Editorial Digital Universitaria de Moa, año 2018
La Editorial Digital Universitaria de Moa publica bajo licencia Creative Commons de
tipo Reconocimiento No Comercial Sin Obra Derivada, se permite su copia y
distribución por cualquier medio siempre que mantenga el reconocimiento de sus
autores, no haga uso comercial de las obras y no realice ninguna modificación de ellas.
La licencia completa puede consultarse en:
http://creativecommons.org/licenses/by-nc-nd/4.0/
Editorial Digital Universitaria
Instituto Superior Minero Metalúrgico
Ave Calixto García Íñiguez # 75, Rpto Caribe Moa 83329, Holguín Cuba
e-mail: edum@ismm.edu.cu
Sitio Web: http://edum.ismm.edu.cu
�Preface
Este folleto es el complemento necesario a los anteriores en los que se enseña
a los estudiantes los elementos gramaticales y el vocabulario general y técnico
requerido para comprender el idioma Inglés con fines profesionales en una
forma adecuada a este nivel de enseñanza. Se le presenta una selección de
textos de la literatura técnica que encontrarán durante su aprendizaje en la
universidad y durante el desarrollo de su profesión. Para ello, se realizó una
investigación que consistió en revisar los libros en inglés relacionados con la
especialidad para seleccionar el vocabulario técnico de mayor uso.
La
ejercitación se concibió con el objetivo de que los estudiantes se apropiaran de
un sistema de conocimientos en este idioma para su posterior generalización y
aplicación, se tuvo en cuenta que el objetivo principal de esta asignatura es leer
y comprender literatura técnica en inglés.
Se presenta además, un glosario de términos mecánicos que tiene como fin
facilitar a los ingenieros y estudiantes de la carrera Ingeniería Mecánica un
soporte para su trabajo.
�Index
Preface
Page
!!!
Theme 1: Strength of Materials.
Reading A: Strength of Materials (Problems and Methods……………….... 1
Reading B: Strength of Materials (Assumptions 1 and 2)………………….
4
Reading C: Strength of Materials (Assumptions 3, 4, 5 and 6) ……………
9
Reading D: Ductility and Brittleness. Hardness…………………………….
14
Reading E: Beams-Shear forces……………………………………………..
17
Theme 2: Machines.
Reading A: Automatic Control of Machine Tools. …………………………
20
Reading B: A car wash for cleaner air………………………………………
22
Reading C: Kinematics………………………………………………………..
25
Reading D: The Centre Lathe…………………………………………………
29
Theme 3: Thermodynamic.
Reading A: Thermodynamics system………………………………………
34
Reading B: Thermodynamics reversibility…………………………………
38
Reading C: The subject of Hydraulics…………………………….…………
42
Theme 4: Cavitations.
Reading A: Cavitations…………………………………………………………. 46
Complementary Texts.
Reading A: Historical Perspective ……………………………………………
Reading B: Some criteria to select the appropriate material ……………..
Glossary………………………………………………………………………….
50
51
53
�
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Libros
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Reading selections for Mechanical Engineering students
Creator
An entity primarily responsible for making the resource
Mirtha Odalis Olivero Herrera
Publisher
An entity responsible for making the resource available
Tania Bess Reyes
Type
The nature or genre of the resource
Libro
Date
A point or period of time associated with an event in the lifecycle of the resource
15 de marzo de 2019
Subject
The topic of the resource
Idioma Inglés
Description
An account of the resource
Libro de apoyo a la docencia en la carrera Mecánica
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
Inglés
-
https://repoedum.ismm.edu.cu/files/original/64ebbb524cf77d73b68d06381a9a6671.pdf
71a12d058e6033659f76dac404697c0a
PDF Text
Text
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Libros
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Technical english. A course for Electrical Engineering students
Creator
An entity primarily responsible for making the resource
Adelfa Verdecia Cruz
Publisher
An entity responsible for making the resource available
Tania Bess Reyes
Type
The nature or genre of the resource
Libro
Date
A point or period of time associated with an event in the lifecycle of the resource
2018
Subject
The topic of the resource
Ingeniería Eléctrica
Description
An account of the resource
Libro básico para la asignatura de Inglés en la carrera de Ingeniería Eléctrica en el Instituto Superior Minero Metalúrgico de Moa
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
Español