The textbook, Design of Machine Elements, was first published in 1994. Since then, number of letters have been received from readers from all over the country, suggesting additions of certain topics which are important for their syllabus. During the same period, there were changes in the Design Office and new trends have come into existence, such as Concurrent Engineering, Design for Manufacture and Assembly (DFMA) and increased emphasis on Statistical considerations like use of Reliability instead of arbitrary value of Factor of Safety in design of machine components. This second edition of the book has been designed keeping the above two factors as guidelines. Following are the key changes that have been made in the revised edition:

(1) A new Chapter 24 on Statistical Considerations in Design is added as per the latest trends. This chapter includes the ‘Probabilistic Approach to Design’ and use of ‘Reliability’ instead of conventional ‘Factor of Safety’ for design of machine components.

(2) Chapter 3 is completely devoted to Design for Manufacture and articles like ‘Design Considerations of Machined Parts’, ‘Design Considerations of Welded Assemblies’ and ‘DFMA’ are added to emphasise the latest trend of ‘Concurrent Engineering’.

(3) There are certain topics which have assumed a lot of importance, such as Fracture Mechanics, Creep, Gerber Equation, Disk Brakes, Ribbed V Belt, Herringbone Gears, Spiral Bevel Gears and Crossed Helical Gears. Although, it is not possible to go into exhaustive detail of these topics, an attempt has been made to introduce these topics in the revised edition.

(4) In order to give broad coverage to the syllabi of various Indian universities, 121 new sections have been added in different chapters.

(5) A number of readers including teachers suggested that the number of solved examples should be increased. In the revised edition 333 solved examples and 202 problems for practice (with answers) are included.

(6) In the design of Spur, Helical and Bevel Gears (Chapters 17, 18 and 19), Buckingham’s Equation of Dynamic Load is used instead of Spott's Equation which was used earlier, as per the suggestion of the teachers. According to Spott’s Equation the magnitude of dynamic load comes out to be very small and unrealistic. It is replaced by the traditional Buckingham’s Equation.

(7) A number of universities ask short answer questions in the examination. The revised edition contains 1438 such questions with answers.

(8) Objective-type questions (multiple-choice) are asked in GATE, UPSC and AMIE examinations. In order to prepare for these examinations 618 objective type questions are posted on the web site of the book, with answers (http://www.mhhe.com/bhandari/dome2e).

(9) Chapter 24 on ‘Computer Aided Design’ has been deleted because separate books are now available on CAD/CAM.

I acknowledge with a deep sense of gratitude, the encouragement and inspiration received from my student, readers and teachers. Suggestions and comments for further improvement of the book will be appreciated.

V B BHANDARI