力學(xué)相關(guān)文獻(xiàn)及其翻譯(共4頁(yè))

1、精選優(yōu)質(zhì)文檔-傾情為你奉上英文原文：1. Introduction to Mechanics of Materials Mechanics of materials is a branch of applied mechanics that deals with the behavior of solid bodies subjected to various types of loading. It is a field of study that is known by a variety of names, including “strength of materials” and “m

2、echanics of deformable bodies.” The solid bodies considered in this book include axially-loaded bars, shafts, beams, and columns, as well as structures that are assemblies of these components. Usually the objective of our analysis will be the determination of the stresses, strains, and deformations

3、produced by the loads; if these quantities can be found for all values of load up to the failure load, then we will have obtained a complete picture of the mechanical behavior of the body.Theoretical analyses and experimental results have equally important roles in the study of mechanics of material

4、s. On many occasions we will make logical derivations to obtain formulas and equations for predicting mechanical behavior, but at the same time we must recognize that these formulas cannot be used in a realistic way unless certain properties of the material are known. These properties are available

5、to us only after suitable experiments have been made in the laboratory. Also, many problems of importance in engineering cannot be handled efficiently by theoretical means, and experimental measurements become a practical necessity. The historical development of mechanics of materials is a fascinati

6、ng blend of both theory and experiment, with experiments pointing the way to useful results in some instances and with theory doing so in others. Such famous men as Leonardo da Vinci(1452-1519) and Galileo Galilei(1564-1642) made experiments to determine the strength of wires, bars, and beams, altho

7、ugh they did not develop any adequate theories (by todays standards) to their test results. By contrast, the famous mathematician Leonhard Euler(1707-1783) developed the mathematical theory of columns and calculated the critical load of a column in 1744, long before any experimental evidence existed

8、 to show the significance of his results. Thus, Eulers theoretical results remained unused for many years, although today they form the basis of column theory.The importance of combining theoretical derivations with experimentally determined properties of materials will be evident as we proceed with

9、 our study of the subject. In this section we will begin by discussing some fundamental concepts, such as stress and strain, and then we will investigate the behavior of simple structural elements subjected to tension, compression, and shear. 2. StressThe concepts of stress and strain can be illustr

10、ated in an elementary way by considering the extension of prismatic bar.A prismatic bar is one that has constant cross section throughout its length and a straight axis. In this illustration the bar is assumed to be loaded at its ends by axial forces P that produce a uniform stretching, or tension,

11、of the bar. By making an artificial cut (section mm) though the bar at right angels to its axis, we can isolate part of the bar as a free body. At the right-hand end the tensile force P is applied, and at the other end there are forces representing the removed portion of the bar upon the part that r

12、emains. These forces will be continuously distributed over the cross section, analogous to the continuous distribution of hydrostatic pressure over a submerged surface. The intensity of force, that is, the per unit area, is called the stress and is commonly denoted by the Greek letter . Assuming tha

13、t the stress has a uniform distribution over the cross section, we can readily see that its resultant is equal to the intensity times the cross-sectional area A of the bar. Furthermore,from the equilibrium of the body shown in Fig, we can also that this resultant must be equal in magnitude and oppos

14、ite in direction to the force P. Hence, we obtain (1)as the equation for the uniform stress in a prismatic bar. This equation shows that stress has units of force divided by area-for example, Newtons per square millimeter (N/mm) or pounds per square inch (psi). When the bar is being stretched by the

15、 forces P, as shown in the figure, the resulting stress is a tensile stress; if the forces are reversed in direction, causing the bar to be compressed, they are called compressive stresses.A necessary condition for Eq. (1) to be valid is that the stress must be uniform over the cross section of the

16、bar. This condition will be realized if the axial force P acts through the centroid of the cross section, as can be demonstrated by statics. When the load P does not act at the centroid, bending of the bar will result, and a more complicated analysis is necessary. Throughout this book, however, it i

17、s assumed that all axial forces are applied at the centroid of the cross section unless specifically stated to the contrary. Also, unless stated otherwise, it is generally assumed that the weight of the object itself is neglected.3. Strain The total elongation of a bar carrying an axial force will b

18、e denoted the Greek letter , and the elongation per unit length, or strain, is then determined by the equation (2)where L is the total length of the bar. Note that the strain is nondimensional quantity. It can be obtained accurately from Eq. (2) as long as the strain is uniform throughout the length

19、 of the bar. If the bar is in tension, the strain is a tensile strain, representing an elongation or a stretching of the material; if the bar is in compression, the strain is a compressive strain, which means that adjacent cross sections of the bar move closer to one another.翻譯：1.材料力學(xué)的介紹 材料力學(xué)是應(yīng)用力學(xué)的一

20、個(gè)分支，用來(lái)處理固體在不同荷載作用下所產(chǎn)生的反應(yīng)。這個(gè)研究領(lǐng)域包含多種名稱(chēng)，如：“材料強(qiáng)度”，“變形固體力學(xué)”。本書(shū)中研究的固體包括受軸向載荷的桿，軸，梁，圓柱及由這些構(gòu)件組成的結(jié)構(gòu)。一般情況下，研究的目的是測(cè)定由荷載引起的應(yīng)力、應(yīng)變和變形物理量；當(dāng)所承受的荷載達(dá)到破壞載荷時(shí)，可測(cè)得這些物理量，畫(huà)出完整的固體力學(xué)性能圖。在材料力學(xué)的研究中，理論分析和實(shí)驗(yàn)研究是同等重要的。必須認(rèn)識(shí)到在很多情況下，通過(guò)邏輯推導(dǎo)的力學(xué)公式和力學(xué)方程在實(shí)際情況中不一定適用，除非材料的某些性能是確定的。而這些性能是要經(jīng)過(guò)相關(guān)實(shí)驗(yàn)的測(cè)定來(lái)得到的。同樣，當(dāng)工程中的重要的問(wèn)題用邏輯推導(dǎo)方式不能有效的解決時(shí)，實(shí)驗(yàn)測(cè)定就發(fā)揮實(shí)用

21、性作用了。材料力學(xué)的發(fā)展歷史是一個(gè)理論與實(shí)驗(yàn)極有趣的結(jié)合，在一些情況下，是實(shí)驗(yàn)的指引得出正確結(jié)果而產(chǎn)生理論，在另一些情況下卻是理論來(lái)指導(dǎo)實(shí)驗(yàn)。例如，著名的達(dá)芬奇(1452-1519)和伽利略(1564-1642)通過(guò)做實(shí)驗(yàn)測(cè)定鋼絲，桿，梁的強(qiáng)度，而當(dāng)時(shí)對(duì)于他們的測(cè)試結(jié)果并沒(méi)有充足的理論支持（以現(xiàn)代的標(biāo)準(zhǔn)）。相反的，著名的數(shù)學(xué)家歐拉(1707-1783) ，在1744年就提出了柱體的數(shù)學(xué)理論并計(jì)算其極限載荷，而過(guò)了很久才有實(shí)驗(yàn)證明其結(jié)果的正確性。 因此，歐拉的理論結(jié)果在很多年里都未被采用，而今天，它們卻是圓柱理論的奠定基礎(chǔ)。隨著研究的不斷深入，把理論推導(dǎo)和在實(shí)驗(yàn)上已確定的材料性質(zhì)結(jié)合起來(lái)研究的重要性將是顯然的。在這一節(jié)，首先。我們討論一些基本概念，如應(yīng)力和應(yīng)變，然后研究受拉伸，壓縮和剪切的簡(jiǎn)單構(gòu)件的性能。2.應(yīng)力通過(guò)對(duì)等截面桿拉伸的研究