Tai ngay!!! Ban co the xoa dong chu MACHINES AND MECHANISMS APPLIED KINEMATIC ANALYSIS Fourth Edition David H. Myszka University of Dayton Prentice Hall Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo Vice President & Editorial Director: Project Manager: Susan Hannahs Vernon R. Anthony Art Director: Jayne Conte Acquisitions Editor: David Ploskonka Cover Designer: Suzanne Behnke Editorial Assistant: Nancy Kesterson Cover Image: Fotolia Director of Marketing: David Gesell Full-Service Project Management: Marketing Manager: Kara Clark Hema Latha, Integra Software Senior Marketing Coordinator: Alicia Services, Pvt Ltd Wozniak Composition: Integra Software Marketing Assistant: Les Roberts Services, Pvt Ltd Senior Managing Editor: JoEllen Gohr Text Printer/Bindery: Edwards Brothers Associate Managing Editor: Alexandrina Cover Printer: Lehigh-Phoenix Color Benedicto Wolf Text Font: 10/12, Minion Production Editor: Maren L. Miller Credits and acknowledgments borrowed from other sources and reproduced, with permission, in this textbook appear on the appropriate page within the text.
Unless otherwise stated, all artwork has been provided by the author. Copyright © 2012, 2005, 2002, 1999 Pearson Education, Inc., publishing as Prentice Hall, One Lake Street, Upper Saddle River, New Jersey, 07458. All rights reserved. Manufactured in the United States of America.
This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission(s) to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, One Lake Street, Upper Saddle River, New Jersey, 07458. Many of the designations by manufacturers and seller to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed in initial caps or all caps.
Library of Congress Cataloging-in-Publication Data Myszka, David H. Machines and mechanisms : applied kinematic analysis / David H. Includes bibliographical references and index. Machinery, Kinematics of.8'11—dc22 2010032839 10 9 8 7 6 5 4 3 2 1 ISBN 10: 0-13-215780-2 ISBN 13: 978-0-13-215780-3 PREFACE The objective of this book is to provide the techniques 6.
Every chapter concludes with at least one case study. necessary to study the motion of machines. A focus is placed on Each case illustrates a mechanism that is used on the application of kinematic theories to real-world machinery. industrial equipment and challenges the student to It is intended to bridge the gap between a theoretical study of discuss the rationale behind the design and suggest kinematics and the application to practical mechanisms.
Students completing a course of study using this book should 7. Both static and dynamic mechanism force analysis be able to determine the motion characteristics of a machine. methods are introduced. The topics presented in this book are critical in machine design 8.
Every major concept is followed by an example process as such analyses should be performed on design con- problem to illustrate the application of the cepts to optimize the motion of a machine arrangement. This fourth edition incorporates much of the feedback received from instructors and students who used the first three 9. Every Example Problem begins with an introduction editions. Some enhancements include a section introducing of a real machine that relies on the mechanism being special-purpose mechanisms; expanding the descriptions of analyzed.
kinematic properties to more precisely define the property; 10. Numerous end-of-chapter problems are consistent clearly identifying vector quantities through standard boldface with the application approach of the text. Every notation; including timing charts; presenting analytical concept introduced in the chapter has at least one synthesis methods; clarifying the tables describing cam fol- associated problem. Most of these problems include lower motion; and adding a standard table used for selection of the machine that relies on the mechanism being chain pitch.
The end-of-chapter problems have been reviewed. In addition, many new problems have been included. Where applicable, end-of-chapter problems are It is expected that students using this book will have a provided that utilize the analytical methods and are good background in technical drawing, college algebra, and best suited for programmable devices (calculators, trigonometry. Concepts from elementary calculus are spreadsheets, math software, etc.
mentioned, but a background in calculus is not required. Also, knowledge of vectors, mechanics, and computer Initially, I developed this textbook after teaching mech- application software, such as spreadsheets, will be useful. anisms for several semesters and noticing that students did However, these concepts are also introduced in the book. not always see the practical applications of the material.
To The approach of applying theoretical developments to this end, I have grown quite fond of the case study problems practical problems is consistent with the philosophy of and begin each class with one. The students refer to this as engineering technology programs. This book is primarily the “mechanism of the day.” I find this to be an excellent oriented toward mechanical- and manufacturing-related opportunity to focus attention on operating machinery. engineering technology programs.
It can be used in either Additionally, it promotes dialogue and creates a learning associate or baccalaureate degree programs. community in the classroom. Following are some distinctive features of this book: Finally, the purpose of any textbook is to guide the students through a learning experience in an effective 1. Pictures and sketches of machinery that contain manner.
I sincerely hope that this book will fulfill this inten- mechanisms are incorporated throughout the text. I welcome all suggestions and comments and can be 2. The focus is on the application of kinematic theories to reached at dmyszka@udayton. common and practical mechanisms.
Both graphical techniques and analytical methods are ACKNOWLEDGMENTS used in the analysis of mechanisms. I thank the reviewers of this text for their comments and 4. An examination copy of Working Model®, a commer- suggestions: Dave Brock, Kalamazoo Valley Community cially available dynamic software package (see Section 2.3 College; Laura Calswell, University of Cincinnati; Charles on page 32 for ordering information), is extensively used Drake, Ferris State University; Lubambala Kabengela, in this book. Tutorials and problems that utilize this University of North Carolina at Charlotte; Sung Kim, software are integrated into the book.
Piedmont Technical College; Michael J. Suggestions for implementing the graphical techniques Northern University; and Gerald Weisman, University of on computer-aided design (CAD) systems are included Vermont. and illustrated throughout the book. Dave Myszka iii CONTENTS 1 Introduction to Mechanisms and 2 Building Computer Models of Kinematics 1 Mechanisms Using Working Model® Objectives 1 Software 31 1.2 Machines and Mechanisms 1 2.2 Computer Simulation of Mechanisms 31 1.3 Obtaining Working Model Software 32 1.4 Using Working Model to Model a Four-Bar 1.6 Kinematic Inversion 8 Mechanism 32 1.5 Using Working Model to Model a Slider- Crank Mechanism 37 1.1 Gruebler’s Equation 8 Problems 41 1.2 Actuators and Drivers 12 1.8 Commonly Used Links and Joints 14 Case Studies 42 1.2 Pin-in-a-Slot Joint 14 3 Vectors 43 1.3 Screw Joint 15 Objectives 43 1.9 Special Cases of the Mobility Equation 16 3.2 Scalars and Vectors 43 1.2 Exceptions to the Gruebler’s 3.3 Graphical Vector Analysis 43 Equation 18 3.4 Drafting Techniques Required in Graphical 1.3 Idle Degrees of Freedom 18 Vector Analysis 44 1.10 The Four-Bar Mechanism 19 3.5 CAD Knowledge Required in Graphical Vector 1.1 Grashof ’s Criterion 19 Analysis 44 1.6 Trigonometry Required in Analytical Vector 1.3 Crank-Rocker 20 Analysis 44 1.5 Change Point Mechanism 20 3.11 Slider-Crank Mechanism 22 3.8 Graphical Vector Addition (+ 7) 48 1.12 Special Purpose Mechanisms 22 3.9 Analytical Vector Addition (+ 7): Triangle 1.1 Straight-Line Mechanisms 22 Method 50 1.10 Components of a Vector 52 1.3 Quick-Return Mechanisms 23 3.11 Analytical Vector Addition (+ 7): Component 1.4 Scotch Yoke Mechanism 23 Method 53 1.13 Techniques of Mechanism Analysis 23 3.1 Traditional Drafting Techniques 24 3.13 Graphical Vector Subtraction (- 7) 55 1.14 Analytical Vector Subtraction (- 7): Triangle 1.3 Analytical Techniques 24 Method 57 1.15 Analytical Vector Subtraction (- 7): Problems 25 Component Method 59 Case Studies 29 3.16 Vector Equations 60 iv Contents v 3.17 Application of Vector Equations 62 5.18 Graphical Determination of Vector 5.3 Timing Charts 110 Magnitudes 63 5.4 Design of Slider-Crank Mechanisms 113 3.19 Analytical Determination of Vector 5.1 In-Line Slider-Crank Mechanism 113 Magnitudes 66 5.2 Offset Slider-Crank Mechanism 114 Problems 67 5.5 Design of Crank-Rocker Mechanisms 115 Case Studies 71 5.6 Design of Crank-Shaper Mechanisms 117 5.7 Mechanism to Move a Link Between Two 4 Position and Displacement Positions 118 Analysis 72 5.1 Two-Position Synthesis with a Pivoting Objectives 72 Link 118 4.2 Two-Position Synthesis of the Coupler of a Four-Bar Mechanism 118 4.8 Mechanism to Move a Link Between Three 4.1 Position of a Point 72 Positions 119 4.2 Angular Position of a Link 72 5.9 Circuit and Branch Defects 119 4.3 Position of a Mechanism 73 Problems 120 4.3 Displacement 73 Case Studies 121 4.4 Displacement Analysis 74 6 Velocity Analysis 123 4.5 Displacement: Graphical Analysis 74 Objectives 123 4.1 Displacement of a Single Driving 6.2 Displacement of the Remaining Slave 6.1 Linear Velocity of Rectilinear Links 75 Points 123 4.6 Position: Analytical Analysis 79 6.2 Linear Velocity of a General 4.1 Closed-Form Position Analysis Equations Point 124 for an In-Line Slider-Crank 81 6.3 Velocity Profile for Linear 4.2 Closed-Form Position Analysis Motion 124 Equations for an Offset Slider- 6.3 Velocity of a Link 125 Crank 84 6.4 Relationship Between Linear and Angular 4.3 Closed-Form Position Equations for a Velocities 126 Four-Bar Linkage 87 6.4 Circuits of a Four-Bar Linkage 87 6.6 Graphical Velocity Analysis: Relative Velocity 4.7 Limiting Positions: Graphical Analysis 87 Method 130 4.8 Limiting Positions: Analytical Analysis 91 6.1 Points on Links Limited to Pure 4.9 Transmission Angle 93 Rotation or Rectilinear 4.10 Complete Cycle: Graphical Position Translation 130 Analysis 94 6.2 General Points on a Floating 4.11 Complete Cycle: Analytical Position Link 132 Analysis 96 6.3 Coincident Points on Different 4.12 Displacement Diagrams 98 Links 135 6.8 Analytical Velocity Analysis: Relative Velocity Problems 101 Method 137 Case Studies 108 6.9 Algebraic Solutions for Common Mechanisms 142 5 Mechanism Design 109 6.1 Slider-Crank Mechanism 142 Objectives 109 6.2 Four-Bar Mechanism 142 5.10 Instantaneous Center of Rotation 142 vi Contents 6.11 Locating Instant Centers 142 7.2 Kennedy’s Theorem 144 Problems 206 6.3 Instant Center Diagram 144 Case Studies 213 6.12 Graphical Velocity Analysis: Instant Center Method 149 8 Computer-Aided Mechanism 6.13 Analytical Velocity Analysis: Instant Center Analysis 215 Method 152 Objectives 215 6.3 User-Written Computer Programs 221 Problems 161 8.1 Offset Slider-Crank Mechanism 221 Case Studies 168 8.2 Four-Bar Mechanism 221 Problems 222 7 Acceleration Analysis 170 Case Study 222 Objectives 170 7.1 Introduction 170 9 Cams: Design and Kinematic 7.2 Linear Acceleration 170 Analysis 223 7.1 Linear Acceleration of Rectilinear Objectives 223 Points 170 9.2 Constant Rectilinear Acceleration 171 9.2 Types of Cams 223 7.3 Acceleration and the Velocity Profile 171 9.3 Types of Followers 224 7.4 Linear Acceleration of a General 9.1 Follower Motion 224 Point 173 9.3 Acceleration of a Link 173 9.4 Prescribed Follower Motion 225 7.2 Constant Angular Acceleration 173 9.5 Follower Motion Schemes 227 7.4 Normal and Tangential Acceleration 174 9.5 Combined Motion Schemes 236 7.6 Graphical Disk Cam Profile Design 237 7.2 Components of Relative 9.1 In-Line Knife-Edge Follower 237 Acceleration 179 9.2 In-Line Roller Follower 238 7.6 Relative Acceleration Analysis: Graphical 9.3 Offset Roller Follower 239 Method 181 9.4 Translating Flat-Faced 7.7 Relative Acceleration Analysis: Analytical Follower 240 Method 188 9.5 Pivoted Roller Follower 241 7.8 Algebraic Solutions for Common 9.7 Pressure Angle 242 Mechanisms 190 9.1 Slider-Crank Mechanism 190 9.9 Analytical Disk Cam Profile 7.2 Four-Bar Mechanism 191 Design 243 7.9 Acceleration of a General Point on a Floating 9.1 Knife-Edge Follower 244 Link 191 9.2 In-Line Roller Follower 246 7.3 Offset Roller Follower 249 7.4 Translating Flat-Faced 7.12 Equivalent Linkages 201 Follower 249 7.5 Pivoted Roller Follower 250 Contents vii 9.