土木工程-土木材料-外文翻译-外文文献-英文文献.doc

《土木工程-土木材料-外文翻译-外文文献-英文文献.doc》由会员分享，可在线阅读，更多相关《土木工程-土木材料-外文翻译-外文文献-英文文献.doc（4页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、Ch 1 Introduction to Mechanics of MaterialsIn all engineering construction the component parts of a structure must assigned definite physical sizes. Such parts must be properly proportioned to resist the actual or probable forces that may be imposed upon them. Thus, the walls of a pressure vessel mu

2、st be of adequate strength to withstand the internal pressure; the floors of a building must be sufficiently strong for their intended purpose; the shaft of a machine must be of adequate size to carry the required torque; a wing of an airplane must safely withstand the aerodynamic loads which may co

3、me upon it in flight or landing. Likewise, the parts of a composite structure must be rigid enough so as not to deflect or sag excessively when in operation under the imposed loads. A floor of a building may be strong enough but yet may deflect excessively, which in some instances may cause misalign

4、ment of manufacturing equipment, or in other cases result in the cracking of a plaster ceiling attached underneath. Also a member may be so thin or slender that, upon being subjected to compressive loading, it will collapse through buckling; i.e., the initial configuration of a member may become uns

5、table. Ability to determine the maximum load that a slender column can carry before buckling occurs or determination of the safe level of vacuum that can be maintained by vessel is of great practical importance.Mechanics of material is a fairly old subject, generally dated from the work of Galileo i

6、n the early part of the seventeenth century. Prior to his investigations into the behavior of solid bodies under loads, constructors followed precedents and empirical rules. Galileo was the first to attempt to explain the behavior of some of the members under load on a rational basis. He studied mem

7、bers in tension and compression, and notably beams used in the construction of hulls of ships for the Italian navy. Of course much progress has been made since that time, but it must noted in passing that much is owed in the development of this subject to the French investigators, among whom a group

8、 of outstanding men such Coulomb, Poisson, Navier, St. Venant, and Cauchy, who worked at the break of the nineteenth century , has left an indelible impression on this subject.The subject of mechanics of materials cuts broadly across all branches of the engineering profession with remarkably many ap

9、plications. Its methods are needed by civil engineers. Each of whom is interested in structures; by mechanical and chemical engineers, who rely upon the methods of this subject for the design of machinery and pressure vessels; by metallurgists, who need the fundamental concepts of this subject in or

10、der to understand how to improve existing materials further; finally, by electrical engineers, who need the methods of this subject because of the importance of the mechanical engineering phases of many portion of electrical equipment. Mechanics of materials has characteristic methods all its own. I

11、t is a definite discipline and one of the most fundamental subjects of an engineering curriculum, standing alongside such other basic subjects as fluid mechanics, thermodynamics, and basic electricity.The behavior of a member subjected to forces depends not only on the fundamental laws of Newtonian

12、mechanics that govern the equilibrium of the forces but also on the physical characteristics of the materials of which the member is fabricated. The necessary information regarding the latter comes from the laboratory where materials are subjected to the action of accurately known forces and the beh

13、avior of test specimens is observed with particular regard to such phenomena as the occurrence of breaks, deformations, etc. Determination of such phenomena is a vital part of the subject, but this branch of the subject is left to other books. Here the end results of such investigations are of inter

14、est, and this course is concerned with the analytical or mathematical part of the subject in contradistinction to experimentation. For the above reasons, it is seen that mechanics of materials is a blended science of experiment and Newtonian postulates of analytical mechanics. From the latter is bor

15、rowed the branch of the science called statics, a subject with which the reader of this book is presumed to be familiar, and on which the subject of this book primarily depends.The subject matter can be mastered best by solving numerous problems. The number of formulas necessary for the analysis and

16、 design of structural and machine members by the methods of mechanics of materials is remarkably small; however, throughout this study the student must develop an ability to visualize a problem and the nature of the quantities being computed. Complete, carefully drawn diagrammatic sketches of problems to be solved will pay large dividends in quicker and more complete mastery of this subject.