Обучение чтению литературы на английском языке по специальности «Прикладная механика» (120

vibration machines rather than by building large vibrators. 4. If the measured result is wanted in the term of velocity rather than in the term of acceleration the use can be made of electronic integrators. 5. The vibrations in aircraft and space vehicles are of a random rather than of a periodic nature.

1. Vertical cracking due to stresses commences at the mid-height. 2. Note, the increase in the crashing strength of the material is due to the biaxial stress conditions. 3. Due to uncertainty of uplift distribution the Federal Energy Regulation Commission (FERC) requires licenses to use conservative uplift pressure assumption in dam stability calculations. 4. The calculation should be made in due time.

1. Since the material does not follow Hooke’s law a theoretical solution becomes very involved. 2. The numerical procedure involved the use of the proposed function in the form suitable for the analysis. 3. One of the groups involved was sponsored by the central Electricity Generating Board (CEGB) of the United Kingdom. 4. The work involving fracture of plates dealt with determination of crack tip angles using strain energy density. 5. An efficient radiator is capable of warming a large room, the process involved is called convection.6. Large deformation process involving visco-plastic materials are considered in this paper.

1. Only the dynamic analysis will yield the correct results when non-conservative forces are involved. 2. Additional calculations might yield a set of buckling equations. 3. The unit stress at the point when deformation continues without increase in stress is known as the yield point. For some materials the yielding is accompanied by a temperature decrease.

7. Translate Text 3C in written form using a dictionary.

Text 3C. Compression Tests

A simple rapid laboratory test is often required for assessing the mechanical properties of metals and for providing data which can be used for solving specific metal working problems. A single test can hardly cover all properties but it allows stress-strain curves to be obtained over as large a range of deformation as possible and provides a measure of ductility at various temperature and strain rates.

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Many conventional mechanical test procedures have been tried in the past with various degrees of success. However, the compression test has been largely neglected mainly because the barreling developed during the deformation of a cylindrical specimen induced a complex and unknown stress system in the material. Hence, the basic stressstrain curve cannot be directly obtained and the conditions leading to failure are difficult to recognize.

Many attempts have been made to understand the stress-strain behavior of materials by compression testing. A group of scientists suggests a new method of assessment of compression test to determine the extent to which it can replace methods in more general use.

According to the authors stress-strain curves can be determined both from special compression tests and by making a correction for barrel development during conventional deformation. The test can provide a general indication of the ductility of a metal. The authors claim that the strain at fracture is in some cases dependent on friction and the geometrical configuration. The authors also give a relation found between barrel development and coefficient of friction.

8. Translate Text 3D from Russian into English.

Text 3D. Ultimate Strength Problems

Если нагрузка на брус продолжает увеличиваться, то напряжение увеличивается тоже, пока не будет достигнуто максимальное напряжение, которое называется пределом прочности. Хрупкий материал разрушается при напряжении до предела прочности, а пластичные материалы продолжают растягиваться. Предел прочности, таким образом, является максимальным напряжением, которое возникает в материале, и определяется по поперечному сечению образца. Поперечное сечение бруса из пластичного материала уменьшается, по мере того как брус нагружается выше точки текучести. После того как предел прочности пластичного материала достигнут, брус начинает образовывать шейку и площадь поперечного сечения быстро уменьшается в месте шейки. Нагрузка на брус в момент разрыва называется разрушающей нагрузкой.

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UNIT 4

New Words and Word Combinations

Appear to the first power — появляться в первой степени Cross product — векторное произведение

Damping — торможение, затухание Forced vibration — вынужденное колебание

Lump continuous system — разбить на части непрерывную систему

Natural frequency — собственная частота

Original equation — исходное уравнение

Oscillate — вибрировать

Principal Mode — основной режим

Principle of superposition — применить принцип наложения

Be referred to — называться, ссылаться Realm — сфера, область

Render possible — считать возможным

1. Read and translate the text.

Text 4A. Theory of Vibration

The study of the motion of physical systems resulting from the forces acting on them is referred to as dynamics, the realm of Newton’s Laws. One type of dynamic behavior of physical systems is vibratory motion, in which the system oscillates about a certain equilibrium position. This motion is rendered possible by the ability of materials used in the construction of systems to store potential energy via their elastic properties.

Most physical systems are continuous in character and their parameters are distributed. In many cases the distributed parameters can be replaced by discrete ones by suitable lumping the continuous system. This should be carried out whenever possible, since lumped parameter systems are described by ordinary differential equations, which are far easier to solve than the partial differential equations describing continuous systems. Having accomplished this, the number of degrees

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of freedom can be established, specifying the number of independent coordinates necessary to define the system.

Oscillatory systems can be classified into two groups according to their behavior, namely linear and non-linear. For a linear system, the principle of superposition is applied, and the dependent variables in the differential equations describing the system appear to the first power only, and also without their cross products.

The number of degrees of freedom chosen dictates the number of differential equations necessary to characterize the system. As these equations are normally coupled to each other, they must be decoupled before their solution is attempted. To do this, the orthogonal properties of the Principal Modes are exploited, enabling the original differential equations to be rewritten in terms of the Principal Coordinates.

A physical system generally exhibits two classes of vibration: free and forced. Free vibration takes place when a system oscillates under the action of forces inherent in the system itself, and when the external forces are absent. The system when given an initial disturbance will vibrate at one or more of its natural frequencies, which are properties of the dynamical system determined by its mass and stiffness distribution. The resulting motion will be the sum of the Principal Modes in some proportion, and will continue move infinitively in the absence of damping. Thus the mathematical study of free vibration yields information about the dynamic properties of the system, relevant for evaluating the response of the system under forced vibration.

Forced Vibration takes place when a system oscillates under the action of external forces. When the excitation force is oscillatory, the system is forced to vibrate at the excitation frequency. If the frequency of excitation coincides with one of the natural frequencies, resonance is encountered, a phenomenon in which the amplitude builds up to dangerously high levels, limited only by the degree of damping.

All physical systems are subjected to one or other type of damping, since energy is dissipated through friction and other resistances. These resistances appear in various forms, after which they are named viscous, hysteretic, Coulomb, aerodynamic etc. The properties of the damping mechanisms differ from each other, and not all of them are equally amenable to mathematical formulation. Fortunately, small amounts of damping have very little influence on the natural frequencies, which are therefore normally calculated assuming no

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damping, as are the Principal Modes of vibration associated with each of these natural frequencies.

2. Match corresponding Russian equivalents to the English word combinations with the word “frequency”.

А. Damped natural frequency, excitation frequency, natural frequency, normal frequency, oscillation frequency, pulse frequency, threshold frequency.

В. Собственная частота, переменная частота, частота импульсов, граничная (возбуждающая) частота, частота колебаний, эталонная частота, частота свободных затухающих колебаний.

3. Translate the sentences paying attention to the translation of underlined words.

1. Once the shape functions have been established the stresses and strains within the element can be determined. 2. Cases where the stress axis is randomly oriented can be analyzed once the stress field is determined. 3.The mechanism failure may occur due to a resonant condition not predicted unless vibration analyses were performed. 4. Since the model of the first true links is derived, modeling of the manipulator is easy. 5. Since the dynamic equations of the model are available they can be used to understand manipulator dynamics. 6. The discussion is included here since the formulation of the problem is very difficult. 7. This computation is the bottleneck of the control system for it involves very many additions and multiplications. 8. A Kalman filter was devised for better estimates of the velocity were to be received. 9. Although the technique is not as general as other techniques it is enough to model most manipulators today. 10. The final failure was abrupt even though (even if) a great deal of cracking might have occurred. 11. TW company has used these failures curves as they fit a wider range of test results. 12. As the tools are used in high velocity mode the welding tablet exhibits a high frequency oscillation. 13. The stress across the test section is uniform provided there is no misalignment.14. While the computational scheme is simple, nevertheless it is exact. 21. An approach to the solution of differential equations of motion has been presented, which results in elastic mechanism analysis. 22. A variation of the procedure which takes large changes into account would be necessary.

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4. Look through Text 4B and answer the following questions.

1. How is the structure dynamic behavior described by analysts and experimentalists? 2. Why is it necessary to find techniques for testing large structures? 3. Why are matrix methods widely used? 4.When did it become possible to measure FRF matrix?

Text 4B. Structure Dynamic Relations

The increasing interest in the structure dynamic behavior has resulted in a lot of literature dealing with what is termed Modal Analysis Techniques. The dynamic behavior of a structure is described by analysts in terms of differential equations as per elemental mass and stiffness, while the experimentalists describe it by its natural frequencies, Principal Modes etc. which are measurable modal parameters. Obviously the mutual collaboration between Principal Modes is a prerequisite for providing data to validate and improve analytical methods, and to verify dynamic design adequacy of the structure.

Thus, the main objective was to find techniques for testing large structures, by using multiple exciters to obtain the frequency response function matrix and to determine methods to improve the modal parameter estimates.

Matrix analysis methods were used on a simple two degree of freedom system to illustrate the concept of orthogonal properties, generalized mass and stiffness, normalization of mode shapes, Principal Coordinates. Since matrix methods expedite the transition to the analysis of multiple degree of freedom system they are used widely.

With the advent of two channel real time analyzers and fast data acquisition equipment it is now possible to measure a single column of a frequency response function (FRF) matrix, by using wide range of random transient signal excitation. By plotting these data, the rest of the FRF matrix can be synthesized, assuming linearity and modal parameters determined. The experimentally measured FRF are curve fitted using algorithms available with these techniques, which yields analytically synthesized FRF.

5. Analyze the sentences and find the subject and the predicate.

1. Table 2 of this paper lists the parameters describing the experimental four bar mechanism. 2. The discontinuities in the plots

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occur whenever the maximum principal stress shifts. 3. Attempting to maintain a constant high velocity results in a path error occurred. 4. The scheme developed partitions the manipulation into two parts. 5. It has been shown that differences in material constants between composite constituents effect stress intensity. 6. During the pressurization process there are stages the stress distribution could not be calculated. 7. Posttension stiffness occurs during the period the load is transferred from the concrete onto the steel.

6. Translate the sentences paying attention to the word-order in the languages.

1. The equations of motion for such systems are presented and their dynamic characteristics dynamic characteristics are examined. 2. The design of an active controller, considering the effect of transport is discussed. 3. A simple modeling and computational scheme for manipulator dynamics has been developed. 4. A simple plane stress concrete element subjected to biaxial compression loading is considered.

7. Translate Text 4C in written form using a dictionary.

Text 4C. Ideal Modal Test

The advantages and disadvantages of the various techniques developed over the course of years will be discussed. Particular impact is placed on the limitation of the different methods to elucidate the reasons for the on-going development of more sophisticated techniques in the continuing search for an ideal modal test.

The simplest and most commonly used technique proves to be ”peak amplitude” method, in which the structure is excited by a sinusoidal force from a single shaker and the “response curve” of total amplitude, obtained at several points on the structure, are recorded as a function of frequency. The required information is then extracted from these curves. However, this method has inherent deficiencies, in that not enough is measured, and what is measured is displayed unsatisfactorily. Some scientists recognized the inadequacies of the method and use vector response plots which is widely used today for estimation of damping and the natural frequencies. The mode shapes

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obtained with this technique, using a single shaker, may not always be acceptable, they will, however, be better than those obtained with the peak amplitude method.

9. Translate Text D from Russian into English.

Text 4D. Plain Concrete Behavior Study

В Миланском технологическом университете на кафедре гражданского строительства была проведена работа по изучению механического поведения чистого бетона под воздействием много осевого напряжения. Требовалось создать математическую модель, которая была бы способна учесть все возможные повреждения: износ, скорость ползучести материала, возникновение и распространение трещин и найти возможные области разрушения в результате ползучести. В литературе не было найдено подходящей модели для описания поведения бетона при высокой температуре. Существующие упруго-пластичные модели предназначались только для однородных (homogeneous) материалов таких как металлы, глина (clay), каменная соль (rock salt). Разработанная модель предназначена для изучения статических и циклических нагрузок. Она характеризуется тензорами повреждения поверхностей, вызванных деформацией растяжения-сжатия. Выведен закон для деформаций, вызванных износом и ползучестью. Результаты проведенного изучения подтверждают надежность данной модели.

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ЛИТЕРАТУРА

Англо-русский физический словарь по надежности и контролю качества. М.: ЭТС, 1999.

Андриевская С.И. Grammar. Приложение к лекциям по сопромату на английском языке. М.: МГТУ им. Н.Э. Баумана, 2009.

Тетради новых терминов № 51 в помощь переводчику. (Англорусские термины по механике разрушения). М.: Всесоюз. центр пер. науч.-техн. лит., 1987.

Тетради новых терминов № 110 b помощь переводчику. (Англорусские термины по методам экспериментальных исследований динамики и прочности). М.: Всесоюз. центр пер. науч.-техн. лит., 1989.

Andrievskaya S.I. Introduction into Strength of Materials in English. Moscow: BMSTU, 2007.

Cambridge English for Engineering. Cambridge University Press, 2009.

Experiments on Strain Rate History and Temperature Effects During the Plastic Deformation of Materials. J. Daffy et al. // Journal of Applied Mechanics. 1988.

Hornby A.S. et al. The advanced Learner’s Dictionary of Current English. London: Oxford University Press, 2000.

Oxford Phrasal Verbs. Oxford University Press, 2006.

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http://www/bentleyuser.org/1.htm

http://darkwing.Uoregon.edu/~struct/courseware/461/461/lectures…html

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CONTENTS
ПРЕДИСЛОВИЕ ..........................................................................................	3
UNIT 1 ..........................................................................................................	4
New Words and Word Combinations..........................................................	4
Text 1A. Unit Stress and Unit Strain...........................................................	4
Text 2B. Allowable and Working Stress .....................................................	6
Text 1C. Crack Study .................................................................................	8
Text 1D. New Mathematical Model ............................................................	9
UNIT 2 ........................................................................................................	10
New Words and Word Combinations........................................................	10
Text 2A. Ultimate Strength. Elastic Limit .................................................	10
Text 2B. Modulus of Elasticity .................................................................	13
Text 2C. Material Behavior Model ...........................................................	15
Text 2D. New Method Development.........................................................	15
UNIT 3 ........................................................................................................	16
New Words and Word Combinations........................................................	16
Text 3A. Stress Strain Diagram and Related Properties .............................	17
Text 3B. Effect of Repeated Stresses. Fatigue. ..........................................	19
Text 3C. Compression Tests.....................................................................	21
Text 3D. Ultimate Strength Problems .......................................................	22
UNIT 4 ........................................................................................................	23
New Words and Word Combinations........................................................	23
Text 4A. Theory of Vibration ...................................................................	23
Text 4B. Structure Dynamic Relations......................................................	26
Text 4C. Ideal Modal Test ........................................................................	27
Text 4D. Plain Concrete Behavior Study...................................................	28
Литература..................................................................................................	29

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