تويت
عندما تؤثر قوة خارجية على الجسم ، يميل الجسم إلى بعض التشوه. بسبب التماسك بين الجزيئات ، يقاوم الجسم التشوه. تُعرف هذه المقاومة التي تقاوم بها مادة الجسم التشوه باسم قوة المادة. ضمن حد معين (أي في المرحلة المرنة) تكون المقاومة التي تقدمها المادة متناسبة مع التشوه الناتج على المادة بواسطة القوة الخارجية. ضمن هذا الحد أيضًا ، تكون المقاومة مساوية للقوة الخارجية (أو الحمل المطبق). ولكن بعد المرحلة المرنة ، تكون المقاومة التي تقدمها المادة أقل من الحمل المطبق. في مثل هذه الحالة ، يستمر التشوه حتى يحدث الفشل. ضمن المرحلة المرنة ، فإن القوة المقاومة تساوي الحمل المطبق. تسمى هذه القوة المقاومة لكل وحدة مساحة الإجهاد أو شدة الإجهاد.
The popularity of the fifth edition and reprints of the bookA Textbook of Strength of Materials amongst the students and the teachers of the various Indian universities, has prompted the bringing out of the sixth edition of the book so soon. The sixth edition has been thoroughly revised and brought up-to-date. A large number of problems from different B.E. degree examinations of Indian universities and other examining bodies, such as Institution of Engineers, U.P.S.C. (Engineering Services) and GATE have been selected and have been solved at proper places in this edition in S.I. Units.
Four advanced topics of Strength of Materials such as stresses due to rotation in thin and thick cylinders, bending of curved bars, theories of failure of the material and unsymmetrical bending and shear centre have been added. These chapters have been written in such a simple and easy-to-follow language that even an average student can understand easily by self-study.
In the chapter of ‘Columns and Struts’, the advanced articles such as columns with eccentric load, with initial curvature and beam columns have been included. Also in the chapter of ‘Principal Stresses and Strains’, strain on an oblique plane and Mohr’s strain circle have been added.
The notations in this edition have been used up-to-date by the use of sigma and tau for stresses.
The objective type multiple-choice questions are often asked in the various competitive examinations. Hence a large number of objective type questions with answers have been added at the end of the book.
Also a large number of objective type questions which have been asked in most of competitive examinations such as Engineering Services Examination and GATE with answers and explanation have been incorporated in this edition.
With these editions, it is hoped that the book will be quite useful for the students of different branches of Engineering at various Engineering Institutions.
I express my sincere thanks to my colleagues, friends, students and the teachers of different Indian universities for their valuable suggestions and recommending the book to their students.
Suggestions for the improvement of this book are most welcome and would be incorpo- rated in the next edition with a view to make the book more useful.
الحجم ١٢ ميغا
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