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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，用来处理固体在不同荷载作用下所产生的反应。这个研究领域包含多种名称，如：“材料强度”，“变形固体力学”。本书中研究的固体包括受轴向载荷的杆，轴，梁，圆柱及由这些构件组成的结构。一般情况下，研究的目的是测定由荷载引起的应力、应变和变形物理量；当所承受的荷载达到破坏载荷时，可测得这些物理量，画出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
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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
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basis of column theory.
在材料力学的研究中，理论分析和实验研究是同等重要的。必须认识到在很多情况下，通过逻辑推导的力学公式和力学方程在实际情况中不一定适用，除非材料的某些性能是确定的。而这些性能是要经过相关实验的测定来得到的。同样，当工程中的重要的问题用逻辑推导方式不能有效的解决时，实验测定就发挥实用性作用了。材料力学的发展历史是一个理论与实验极有趣的结合，在一些情况下，是实验的指引得出正确结果而产生理论，在另一些情况下却是理论来指导实验。例如，著名的达芬奇(1452-1519)和伽利略(1564-1642)通过做实验测定钢丝，杆，梁的强度，而当时对于他们的测试结果并没有充足的理论支持（以现代的标准）。相反的，著名的数学家欧拉(1707-1783) ，在1744年就提出了柱体的数学理论并计算其极限载荷，而过了很久才有实验证明其结果的正确性。 因此，欧拉的理论结果在很多年里都未被采用，而今天，它们却是圆柱理论的奠定基础。 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，
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材料力学的介绍(专业英语)
