Tai ngay!!! Ban co the xoa dong chu nay!! This page intentionally left blank MECHANICAL DESIGN OF MACHINE ELEMENTS AND MACHINES Second Edition This page intentionally left blank MECHANICAL DESIGN OF MACHINE ELEMENTS AND MACHINES A Failure Prevention Perspective Second Edition Jack A. Staab The Ohio State University John Wiley & Sons VP & EXECUTIVE PUBLISHER Don Fowley ACQUISITIONS EDITOR Michael McDonald PRODUCTION MANAGER Dorothy Sinclair SENIOR PRODUCTION EDITOR Sandra Dumas MARKETING MANAGER Christopher Ruel SENIOR DESIGNER Kevin Murphy PRODUCTION MANAGEMENT SERVICES Thomson Digital EDITORIAL ASSISTANT Renata Marchione MEDIA EDITOR Lauren Sapira COVER PHOTO Professor Anthony Luscher This book was set in Times Roman by Thomson Digital and printed and bound by R. The cover was printed by Phoenix Color. This book is printed on acid free paper.
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Return instructions and a free of charge return shipping label are available at www.com/go/returnlabel. Outside of the United States, please contact your local representative. ISBN-13 978-0-470-41303-6 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Preface This new undergraduate book, written primarily to support a Junior-Senior level sequence of courses in Mechanical Engineering Design, takes the viewpoint that failure prevention is the cornerstone concept underlying all mechanical design activity. The text is presented in two parts, Part I—Engineering Principles, containing 7 chapters, and Part II—Design Applications, containing 13 Chapters.
Because of the way the book is organized it also may be conveniently used as the basis for continuing education courses or short-courses directed toward graduate engineers, as well as a reference book for mechanical designers engaged in professional practice. Organization Part I introduces the design viewpoint and provides analytical support for the mechani- cal engineering design task. Analysis is characterized by known material, known shape, known dimensions and known loading. The results of analyses usually include the calcu- lation of stresses, strains or existing safety factors.
Techniques are presented for failure mode assessment, material selection, and safety factor selection. A unique chapter on geometry determination provides basic principles and guidelines for creating efficient shapes and sizes. A case is made for integration of manufacturing, maintenance, and crit- ical point inspection requirements at the design stage, before the machine is built. Part II expands on the design viewpoint introduced in Part I.
Design is a task char- acterized by known specifications, and nothing more. The results of design usually include picking a material, picking a design safety factor, conceiving a shape, and determining dimensions that will safely satisfy the design specifications in the “best” possible way. Key Text Features 1. Comprehensive coverage of failure modes.
Basic tools are introduced for recognizing potential failure modes that may govern in any specific design scenario. At a mini- mum, the topics of elastic deformation, yielding brittle fracture, fatigue, buckling, and impact should be considered by the instructor. 1 Chapter 2 presents a condensed and simplified version of sections of Failure of Materials in Mechanical Design: Analysis Prediction, Prevention. Modern coverage of materials selection (Chapter 3).
The materials selection concepts presented introduce some new ideas and are a virtual necessity for any competent de- sign engineer. Failure theories and related topics (Chapter 5). Topics which play a significant role in identifying failure (multiaxial states of stress and stress concentrations) are presented as a prelude to static and fatigue failure theories as well as brittle fracture and crack growth. Guidelines for creating efficient shapes and sizes for components and machines (Chapter 6).
This important chapter, covering material rarely discussed in other design textbooks, is a “must” for any modern course covering the design of machine elements. Concurrent engineering and “Design-for-X” ideas (Chapter 7). These are important in modern manufacturing practice and should be introduced in a well-rounded course in mechanical engineering design. Conceptual introductions to machine elements (Chapters 8 through 19).
Organized and designed to be especially helpful to students who may have had little or no expo- sure to machines, structures, or industrial practice, each chapter in Part II follows a consistent introductory pattern: • “Uses and Characteristics”—What does it look like? What does it do? What varia- tions are available? • “Probable failure modes”—based on practical experience. • “Typical materials used for the application”—based on common design practice. These introductory sections are followed in each chapter by detailed discussions about analyzing, selecting, or designing the component under consideration. Inclusion of latest available revisions of applicable codes and standards for well- standardized elements such as gears, rolling-element bearings, V-belts, precision roller-chain, and others.
Selected up-to-date supporting data have been included for many commercially available components, such as rolling-element bearings, V-belts, wire rope, and flexible shafts, Many manufacturers’catalogs have been included in the reference lists. Clear sketches and detailed tables to support virtually all of the important design and selection issues discussed. Illuminating footnotes, anecdotes, experience-based observations, and contemporary- event illustrations, to demonstrate the importance of good design decision-making. Worked Examples and Homework Problems Nearly 100 worked examples have been integrated with the text.
Of these worked exam- ples, about half are presented from a design viewpoint, including about 1⁄4 of the examples given in Part I, and about 3⁄4 of the examples given in Part II. The remainder are presented from the more traditional analysis viewpoint. End-of-chapter problems have been distilled, in great measure, from real design proj- ects encountered by the author in consulting, research, and short-course interaction with engineers in industry, then filtered through more than three decades of student homework assignments and design-course examinations. It is the author's hope that students (and instructors) will find the problems interesting, realistic, instructional, challenging, and solvable.
Preface / vii To supplement the worked examples, a companion web site at www.com/ college/collins has been developed to provide more than 100 additional variations and extensions of the examples worked in the text. Many of the website variations and exten- sions require solution techniques based on standard computer codes such as MATLAB® or Mathcad ®. Additional instructor and student resources, such as errata listings, also are posted at the website. Suggestions for Course Coverage Although it is presumed that the user has had basic courses in Physics, Materials Engineering, Statics and Dynamics, and Strength of Materials, most concepts from these courses that are needed for basic mechanical engineering design activity have been sum- marized and included in Part I, primarily in Chapters 2,3, 4, and 5.
Accordingly, an in- structor has great flexibility in selecting material to be covered, depending upon the preparation of students coming in the course. For example, if students are well prepared in strength-of-materials concepts, only the last half of Chapter 4 needs to be covered.5 may readily be skipped, yet the material is available for refer- ence.10 contain important design related material not ordinarily covered in standard strength-of-materials courses. The three-part introduction to each “elements” chapter makes it possible to offer a (superficial) descriptive survey course on machine elements by covering only the first few sections of each chapter in Part II. Although such an approach would not, by itself, be especially appropriate in educating a competent designer, it would provide the potential for remarkable flexibility in tailoring a course sequence that could introduce the student to all machine elements of importance (by assigning the first few sections of each chapter of Part II), then covering in depth the chapters selected by the supervisory design-faculty- group, or the instructor, to fit into the designated curricular time frame.
With few exceptions, the machine element chapters (8 through 19) have been written as stand-alone units, independent of each other, each resting upon pertinent principles dis- cussed in Part I. This presentation philosophy affords an instructor great flexibility in for- mulating a sequence of machine-element topics, in any order, that is compatible with his or her priorities, philosophy, and experience. Supplements An instructor’s solution manual is available, providing comprehensive solutions for all end-of-chapter problems. Please contact your local Wiley representative for details.
Acknowledgments As time progresses, it is difficult, if not impossible, to distinguish one’s own original thoughts from the thoughts gathered through reading and discussing the works of others. For those who find their essence in these pages without specific reference, we wish to ex- press our appreciation. In particular, Professor Collins expresses deep appreciation to Professors Walter L. Starkey and the late Professor S.
Marco, who were his professors while he was a student. Much of their philosophy has no doubt been adopted by Professor Collins. Professor Starkey's fertile mind created many of the innovative concepts presented viii / Preface in Chapters 2, 3, 6, and 7 of this text. Professor Starkey is held in the highest esteem as an outstanding engineer, innovative designer, inspirational teacher, gentleman, and friend.
Gratitude is also expressed for colleagues at Ohio State who reviewed and contributed to various parts of the manuscript. In particular, Professor E. Parker, and Professor Brian D. Reviewers always play an important role in the development of any textbook.
We would like to express our appreciation to those who reviewed the first edition of this text and made valuable comments and suggestions for the second edition, including Richard E., Kettering University; Antoinette Maniatty, Rensselaer Polytechnic Institute; Eberhard Bamberg, University of Utah; Jonathan Blotter, Brigham Young University; Vladimir Glozman, California State Polytechnic University, Pomona; John P. Steele, Colorado School of Mines; John K. Schueller, University of Florida; and Ken Youssefi, University of California, Berkeley. Thanks are also due to Joseph P.
Hayton for seeing the benefit in pursuing a second edition, and Michael McDonald, Editor for carrying through with the project. In addition, we wish to thank the many other individuals in the John Wiley & Sons, Inc. organization who have contributed their talents and energy to the production of this book. Finally, we wish to express our thanks to our wives.
In particular, Professor Collins’wife, JoAnn, for transforming the hand-written pages into a typed manuscript for the first edition of this text. Professor Collins wishes to dedicate his contributions in this work to his wife, Jo Ann, his children Mike, (Julie), Jennifer, (Larry), Joan, Greg, (Heather), and his grandchil- dren, Michael, Christen, David, Erin, Caden, and Marrec. Staab Contents PART ONE ENGINEERING PRINCIPLES Chapter 1 Columns with Other End Constraints 38 Keystones of Design: Materials Inelastic Behavior and Initially Crooked Selection and Geometry Determination 1 Columns 39 1.1 Some Background Philosophy 1 Column Failure Prediction and Design 1.2 The Product Design Team 2 Considerations 40 1.3 Function and Form; Aesthetics and Buckling of Elements Other Than Columns 43 Ergonomics 5 2.6 Shock and Impact 46 1.4 Concepts and Definition of Mechanical Stress Wave Propagation Under Impact Loading Design 6 Conditions 46 1.5 Design Safety Factor 7 Energy Method of Approximating Stress and Deflection Under Impact Loading 1.6 Stages of Design 7 Conditions 47 1.7 Steps in the Design Process 9 2.7 Creep and Stress Rupture 52 1.8 Fail Safe and Safe Life Design Concepts 9 Predictions of Long-Term Creep Behavior 53 1.9 The Virtues of simplicity 10 Creep under Uniaxial State of Stress 55 1.