力学专业英语1应力与应变

2. Stress 应力 The concepts of stress and strain can be illustrated in an elementary way by considering the extension of prismatic bar [see Fig.1.4(a)]. 通过对等 截面杆拉伸的研究初步解释应力和应变的概念 [ 如图 1.4 （ a ） ] 。 A prismatic bar is one that has constant cross section throughout its length and a straight axis. 等截面杆是一个具有恒定截面的直线轴。In this illustration the bar is assumed to be loaded at its ends by axial forces P that produce a uniform stretching, or tension, of the bar. 这里，假设在杆 的末端施加轴向力 P，产生均匀的伸展或拉伸。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 [Fig.1.4 (b)]. 假设沿垂直于轴线的方向切 割杆，我们就能把杆的一部分当作自由体隔离出来[图 1.4（b）]。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 remains. 张力 P 作用于杆的右端， 在另一端就会出现一些力来代表杆 被切除的那一部分。These forces will be continuously distributed over the cross section, analogous to the continuous distribution of hydrostatic pressure over a submerged surface. 这些力连续的分布在横截面上，类 似于作用在被淹没物体表面的连续的静水压力。 The intensity of force, that is, the per unit area, is called the stress and is commonly denoted by the Greek letter .力的密度，也就是单位面积上的力的大小称为应 力，一般用 表示。Assuming that the stress has a uniform distribution
over the cross section [see Fig.1.4(b)], we can readily see that its resultant is equal to the intensity times the cross-sectional area A of the bar. 假 设应力是均匀分布在横截面上[如图 1.4（b）]，我们很容易得出它的 大小等于密度 乘以杆的横截面积 A。Furthermore,
experimentally determined properties of materials will be evident as we proceed with 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. 随着研究的不断深入， 把理论推导和在实验上已确定的材料性质 结合起来研究的重要性将是显然的。在这一节，首先。我们讨论一些 基本概念，如应力和应变，然后研究受拉伸，压缩和剪切的简单构件 的性能。
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 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 fascinating 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, although they did not develop any adequate theories (by today’s 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 to show the significance of his results. Thus, Euler ’s theoretical results remained unused for many years, although today they form the basis of column theory. 在材料力学的研究中，理论分析和实验研究同等重要。很多情况 下，我们通过逻辑推导来获得预测力学性能的公式和方程，但同时我
应力和ቤተ መጻሕፍቲ ባይዱ变
1. Introduction to Mechanics of Materials 材料力学的介绍 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 “mechanics 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 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. 材料力学是应用力学的一个分支，涉及受不同类型载荷的固体的 性能。这是一个有多种名称的研究领域，包括： “材料强度” ， “易变 形体的力学” 。本书中研究的固体包括受轴向载荷的杆，轴，梁，圆 柱和由这些零件装配的机构。一般情况下，我们研究的目的是测定因 受载而引起的应力， 应变和变形； 如果当所有负荷量达到破坏载荷时， 能够测得这些物理量，我们就可能得到一份完整的固体力学性能图。 Theoretical analyses and experimental results have equally important roles in the study of mechanics of materials. On many