521
CHAPTER 9 DESIGN CASE STUDIES ____________________________________ 523
9.0
Introduction ................................................................................................. 523
9.1
Case Study 8A: Preliminary Design of a Compressor Drive Train ............. 526
9.2
Case Study 9A: Preliminary Design of a Winch Lift .................................. 528
9.3
Case Study 10A: Preliminary Design of a Cam Dynamic Test Fixture ...... 532
9.4
Summary ...................................................................................................... 537
9.5
References .................................................................................................... 537
9.6
Design Projects ............................................................................................ 538
CHAPTER 10 SHAFTS, KEYS, AND COUPLINGS _____________________________ 549
10.0 Introduction ................................................................................................. 549
10.1 Shaft Loads ................................................................................................... 549
10.2 Attachments and Stress Concentrations ....................................................... 551
10.3 Shaft Materials .............................................................................................. 553
10.4 Shaft Power .................................................................................................. 553
10.5 Shaft Loads ................................................................................................... 554
10.6 Shaft Stresses ................................................................................................ 554
10.7 Shaft Failure in Combined Loading............................................................... 555
10.8 Shaft Design ................................................................................................. 556
General Considerations
556
Design for Fully Reversed Bending and Steady Torsion
557
Design for Fluctuating Bending and Fluctuating Torsion
559
10.9 Shaft Deflection ........................................................................................... 566
Shafts as Beams
567
Shafts as Torsion Bars
567
10.10 Keys and Keyways ........................................................................................ 570
Parallel Keys
570
Tapered Keys
571
Woodruff Keys
572
Stresses in Keys
572
Key Materials
573
Key Design
573
Stress Concentrations in Keyways
574
10.11 Splines ........................................................................................................... 578
10.12 Interference Fits ............................................................................................ 580
Stresses in Interference Fits
580
Stress Concentration in Interference Fits
581
Fretting Corrosion
582
10.13 Flywheel Design ........................................................................................... 585
Energy Variation in a Rotating System
586
Determining the Flywheel Inertia
588
Stresses in Flywheels
590
Failure Criteria
591
xv
10.14 Critical Speeds of Shafts ............................................................................... 593
Lateral Vibration of Shafts and Beams—Rayleigh’s Method
596
Shaft Whirl
597
Torsional Vibration
599
Two Disks on a Common Shaft
600
Multiple Disks on a Common Shaft
601
Controlling Torsional Vibrations
602
10.15 Couplings ..................................................................................................... 604
Rigid Couplings
605
Compliant Couplings
606
10.16 Case Study .................................................................................................... 608
Case Study 8B: Preliminary Design of Shafts for a Compressor Drive Train 608
10.17 Summary ..................................................................................................... 612
10.18 References.................................................................................................... 614
10.19 Problems ...................................................................................................... 615
CHAPTER 11 BEARINGS AND LUBRICATION _______________________________ 623
11.0 Introduction ................................................................................................. 623
11.1 Lubricants .................................................................................................... 625
11.2 Viscosity ....................................................................................................... 627
11.3 Types of Lubrication ..................................................................................... 628
Full-Film Lubrication
629
Boundary Lubrication
631
11.4 Material Combinations in Sliding Bearings ................................................ 631
11.5 Hydrodynamic Lubrication Theory ............................................................... 632
Petroff’s Equation for No-Load Torque
633
Reynolds’ Equation for Eccentric Journal Bearings
634
Torque and Power Losses in Journal Bearings
639
11.6 Design of Hydrodynamic Bearings .............................................................. 640
Design Load Factor—The Ocvirk Number
640
Design Procedures
642
11.7 Nonconforming Contacts ............................................................................ 646
11.8 Rolling-element bearings ............................................................................. 653
Comparison of Rolling and Sliding Bearings
654
Types of Rolling-Element Bearings
654
11.9 Failure of Rolling-Element bearings ............................................................. 658
11.10 Selection of Rolling-Element bearings ......................................................... 659
Basic Dynamic Load Rating C
659
Modified Bearing Life Rating
660
Basic Static Load Rating C0
661
Combined Radial and Thrust Loads
662
Calculation Procedures
663
11.11 Bearing Mounting Details ............................................................................ 665
11.12 Special Bearings ........................................................................................... 666
11.13 Case Study .................................................................................................... 668
Case Study 10B: Design of Hydrodynamic Bearings for a Cam Test Fixture 668
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11.14 Summary ...................................................................................................... 670
11.15 References .................................................................................................... 673
11.16 Problems ...................................................................................................... 675
CHAPTER 12 SPUR GEARS ____________________________________________ 681
12.0 Introduction ................................................................................................. 681
12.1 Gear Tooth Theory ........................................................................................ 683
The Fundamental Law of Gearing
683
The Involute Tooth Form
684
Pressure Angle
685
Gear Mesh Geometry
686
Rack and Pinion
687
Changing Center Distance
687
Backlash
689
Relative Tooth Motion
689
12.2 Gear Tooth Nomenclature ............................................................................. 689
12.3 Interference and Undercutting ...................................................................... 692
Unequal-Addendum Tooth Forms
693
12.4 Contact Ratio ................................................................................................. 694
12.5 Gear Trains ................................................................................................... 696
Simple Gear Trains
696
Compound Gear Trains
697
Reverted Compound Trains
698
Epicyclic or Planetary Gear Trains
699
12.6 Gear Manufacturing ..................................................................................... 702
Forming Gear Teeth
702
Machining
703
Roughing Processes
703
Finishing Processes
705
Gear Quality
705
12.7 Loading on Spur Gears ................................................................................. 706
12.8 Stresses in Spur Gears ................................................................................... 708
Bending Stresses
709
Surface Stresses
718
12.9 Gear Materials .............................................................................................. 722
Material Strengths
723
AGMA Bending-Fatigue Strengths for Gear Materials
724
AGMA Surface-Fatigue Strengths for Gear Materials
725
12.10 Lubrication of Gearing .................................................................................. 732
12.11 Design of Spur Gears ................................................................................... 732
12.12 Case Study .................................................................................................... 734
Case Study 8C: Design of Spur Gears for a Compressor Drive Train 734
12.13 Summary ...................................................................................................... 738
12.14 References .................................................................................................... 741
12.15 Problems ...................................................................................................... 742
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CHAPTER 13 HELICAL, BEVEL, AND WORM GEARS _________________________ 747
13.0 Introduction ................................................................................................. 747
13.1 Helical Gears ................................................................................................ 747
Helical Gear Geometry
749
Helical-Gear Forces
750
Virtual Number of Teeth
751
Contact Ratios
752
Stresses in Helical Gears
752
13.2 Bevel Gears .................................................................................................. 760
Bevel-Gear Geometry and Nomenclature
761
Bevel-Gear Mounting
762
Forces on Bevel Gears
762
Stresses in Bevel Gears
763
13.3 Wormsets .................................................................................................... 768
Materials for Wormsets
770
Lubrication in Wormsets
770
Forces in Wormsets
770
Wormset Geometry
770
Rating Methods
771
A Design Procedure for Wormsets
773
13.4 Case Study .................................................................................................... 774
Case Study 9B: Design of a Wormset Speed Reducer for a Winch Lift 774
13.5 Summary ..................................................................................................... 777
13.6 References ................................................................................................... 781
13.7 Problems ...................................................................................................... 782
CHAPTER 14 SPRING DESIGN __________________________________________ 785
14.0 Introduction ................................................................................................. 785
14.1 Spring Rate ................................................................................................... 785
14.2 Spring Configurations ................................................................................. 788
14.3 Spring Materials ........................................................................................... 790
Spring Wire
790
Flat Spring Stock
793
14.4 Helical Compression Springs ........................................................................ 795
Spring Lengths
796
End Details
796
Active Coils
797
Spring Index
797
Spring Deflection
797
Spring Rate
797
Stresses in Helical Compression Spring Coils
798
Helical Coil Springs of Nonround Wire
799
Residual Stresses
800
Buckling of Compression Springs
802
Compression–Spring Surge
802
Allowable Strengths for Compression Springs
803
The Torsional-Shear S-N Diagram for Spring Wire
804
The Modified-Goodman Diagram for Spring Wire
806
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14.5 Designing Helical Compression Springs for Static Loading ........................ 808
14.6 Designing Helical Compression Springs for Fatigue Loading .................... 812
14.7 Helical Extension Springs .............................................................................. 820
Active Coils in Extension Springs
821
Spring Rate of Extension Springs
821
Spring Index of Extension Springs
821
Coil Preload in Extension Springs
821
Deflection of Extension Springs
822
Coil Stresses in Extension Springs
822
End Stresses in Extension Springs
822
Surging in Extension Springs
823
Material Strengths for Extension Springs
823
Design of Helical Extension Springs
824
14.8 Helical Torsion Springs .................................................................................. 831
Terminology for Torsion Springs
832
Number of Coils in Torsion Springs
832
Deflection of Torsion Springs
832
Spring Rate of Torsion Springs
833
Coil Closure
833
Coil Stresses in Torsion Springs
833
Material Parameters for Torsion Springs
834
Safety Factors for Torsion Springs
835
Designing Helical Torsion Springs
836
14.9 Belleville Spring Washers ............................................................................. 838
Load-Deflection Function for Belleville Washers
840
Stresses in Belleville Washers
841
Static Loading of Belleville Washers
842
Dynamic Loading
842
Stacking Springs
842
Designing Belleville Springs
843
14.10 Case Studies ................................................................................................. 845
Case Study 10C: Design of a Return Spring for a Cam-Follower Arm 846
14.11 Summary ...................................................................................................... 850
14.12 References .................................................................................................... 853
14.13 Problems ...................................................................................................... 854
CHAPTER 15 SCREWS AND FASTENERS __________________________________ 859
15.0 Introduction ................................................................................................. 859
15.1 Standard Thread Forms ................................................................................. 862
Tensile Stress Area
863
Standard Thread Dimensions
864
15.2 Power Screws ............................................................................................... 865
Square, Acme, and Buttress Threads
865
Power Screw Application
866
Power Screw Force and Torque Analysis
868
Friction Coefficients
869
Self-Locking and Back-Driving of Power Screws
870
Screw Efficiency
871
Ball Screws
872
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15.3 Stresses in Threads ....................................................................................... 874
Axial Stress
875
Shear Stress
875
Torsional Stress
876
15.4 Types of Screw Fasteners .............................................................................. 876
Classification by Intended Use
877
Classification by Thread Type
877
Classification by Head Style
877
Nuts and Washers
879
15.5 Manufacturing Fasteners ............................................................................ 880
15.6 Strengths of Standard Bolts and Machine Screws ...................................... 881
15.7 Preloaded Fasteners in Tension .................................................................... 882
Preloaded Bolts Under Static Loading
885
Preloaded Bolts Under Dynamic Loading
890
15.8 Determining the Joint Stiffness Factor ....................................................... 895
Joints With Two Plates of the Same Material
897
Joints With Two Plates of Different Materials
898
Gasketed Joints
899
15.9 Controlling Preload ..................................................................................... 904
The Turn-of-the-Nut Method
905
Torque-Limited Fasteners
905
Load-Indicating Washers
905
Torsional Stress Due to Torquing of Bolts
906
15.10 Fasteners in Shear ......................................................................................... 907
Dowel Pins
908
Centroids of Fastener Groups
909
Determining Shear Loads on Fasteners
910
15.11 Case Study .................................................................................................... 912
Designing Headbolts for an Air Compressor
912
Case Study 8D: Design of the Headbolts for an Air Compressor
912
15.12 Summary ..................................................................................................... 917
15.13 References.................................................................................................... 920
15.14 Bibliography ................................................................................................. 921
15.15 Problems ...................................................................................................... 921
CHAPTER 16 WELDMENTS ____________________________________________ 927
16.0 Introduction ................................................................................................. 927
16.1 Welding Processes....................................................................................... 929
Types of Welding in Common Use
930
Why Should a Designer Be Concerned with the Welding Process?
931
16.2 Weld Joints and Weld Types ....................................................................... 931
Joint Preparation
933
Weld Specification
933
16.3 Principles of Weldment Design .................................................................... 934
16.4 Static Loading of Welds ............................................................................... 936
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16.5 Static Strength of Welds ............................................................................... 936
Residual Stresses in Welds
937
Direction of Loading
937
Allowable Shear Stress for Statically Loaded Fillet and PJP Welds 937
16.6 Dynamic Loading of Welds ......................................................................... 940
Effect of Mean Stress on Weldment Fatigue Strength
940
Are Correction Factors Needed For Weldment Fatigue Strength?
940
Effect of Weldment Configuration on Fatigue Strength
941
Is There an Endurance Limit for Weldments?
945
Fatigue Failure in Compression Loading?
945
16.7 Treating a Weld as a Line ............................................................................. 947
16.8 Eccentrically Loaded Weld Patterns ............................................................. 952
16.9 Design Considerations for Weldments in Machines .................................... 954
16.10 Summary ...................................................................................................... 955
16.11 References .................................................................................................... 956
16.12 Problems ...................................................................................................... 956
CHAPTER 17 CLUTCHES AND BRAKES ___________________________________ 959
17.0 Introduction ................................................................................................. 959
17.1 Types of Brakes and Clutches ...................................................................... 961
17.2 Clutch/Brake Selection and Specification ..................................................... 966
17.3 Clutch and Brake Materials ........................................................................... 968
17.4 Disk Clutches ............................................................................................... 968
Uniform Pressure
969
Uniform Wear
969
17.5 Disk Brakes .................................................................................................. 971
17.6 Drum Brakes ................................................................................................. 972
Short-Shoe External Drum Brakes
973
Long-Shoe External Drum Brakes
975
Long-Shoe Internal Drum Brakes
979
17.7 Summary ...................................................................................................... 979
17.8 References .................................................................................................... 982
17.9 Bibliography ................................................................................................. 982
17.10 Problems ...................................................................................................... 983
APPENDIX A MATERIAL PROPERTIES ____________________________________ 987
APPENDIX B BEAM TABLES __________________________________________ 995
APPENDIX C STRESS–CONCENTRATION FACTORS __________________________ 999
APPENDIX D ANSWERS TO SELECTED PROBLEMS
1007
INDEX
1017
Preface
Introduction
This text is intended for the Design of Machine Elements courses typically given in the junior year of most mechanical engineering curricula. The usual prerequisites are a first course in Statics and Dynamics, and one in Strength of Materials. The purpose of this book is to present the subject matter in an up-to-date manner with a strong design emphasis. The level is aimed at junior-senior mechanical engineering students. A primary goal was to write a text that is very easy to read and that students will enjoy reading despite the inherent dryness of the subject matter.
This textbook is designed to be an improvement over others currently available and to provide methods and techniques that take full advantage of computer-aided analysis. It emphasizes design and synthesis as well as analysis. Example problems, case studies, and solution techniques are spelled out in detail and are self-contained. All the illustrations are done in two colors. Short problems are provided in each chapter and, where appropriate, longer unstructured design-project assignments are given.
The book is independent of any particular computer program. Computer files for the solution of all the examples and case studies written in several different languages (Mathcad, MATLAB, Excel, and TK Solver) are provided on the CD-ROM. Several other programs written by the author are also provided as executable files. These include a Mohr’s circle generator (MOHR.exe), dynamic surface stress calculator (CONTACT.exe), matrix solver (MATRIX.exe) and several linkage and cam design programs. An index of the CD-ROM’s content is on the CD.
While this book attempts to be thorough and complete on the engineering-mechanics topics of failure theory and analysis, it also emphasizes the synthesis and design aspects of the subject to a greater degree than most other texts in print on this subject. It points out the commonality of the analytical approaches needed to design a wide variety of elements and emphasizes the use of computer-aided engineering as an approach to the design and analysis of these classes of problems. The author’s approach to this course is based on 50 years of practical experience in mechanical engineering design, both in industry and as a consultant. He has taught mechanical engineering design at the university level for 30 of those years as well.
What’s New in the Fourth Edition?
• A new chapter on the design of weldments presents the latest data and methods on this topic.
• The chapter on finite element analysis (FEA) has been moved from Chapter 16 to Chapter 8 and augmented with additional FEA solutions for case studies that are developed in earlier chapters.
• Solidworks models with FEA solutions to several of the case studies are provided on the CD-ROM.
• Solidworks models of many assigned problems’ geometry are provided on the CD-ROM to expedite FEA solutions of those problems at the instructor’s option.
• A new technique for the computation of bolted-joint stiffness is presented in Chapter 15 on Fasteners.
• Over 150 problems are added or revised with an emphasis on SI units.
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Philosophy
This is often the first course that mechanical engineering students see that presents them with design challenges rather than set-piece problems. Nevertheless, the type of design addressed in this course is that of detailed design, which is only one part of the entire design-process spectrum. In detailed design, the general concept, application, and even general shape of the required device are typically known at the outset. We are not trying to invent a new device so much as define the shape, size, and material of a particular machine element such that it will not fail under the loading and environmental conditions expected in service.
The traditional approach to the teaching of the Elements course has been to emphasize the design of individual machine parts, or elements, such as gears, springs, shafts, etc. One criticism that is sometimes directed at the Elements course (or textbook) is that it can easily become a “cookbook” collection of disparate topics that does not prepare the student to solve other types of problems not found in the recipes presented. There is a risk of this happening. It is relatively easy for the instructor (or author) to allow the course (or text) to degenerate into the mode
“Well it’s Tuesday, let’s design springs—on Friday, we’ll do gears.” If this happens, it may do the student a disservice because it doesn’t necessarily develop a fundamental understanding of the practical application of the underlying theories to design problems.
However, many of the machine elements typically addressed in this course provide superb examples of the underlying theory. If viewed in that light, and if presented in a general context, they can be an excellent vehicle for the development of student understanding of complex and important engineering theories. For example, the topic of preloaded bolts is a perfect vehicle to introduce the concept of prestressing used as a foil against fatigue loading. The student may never be called upon in practice to design a preloaded bolt, but he or she may well utilize the understanding of prestressing gained from the experience. The design of helical gears to withstand time-varying loads provides an excellent vehicle to develop the student’s understanding of combined stresses, Hertzian stresses, and fatigue failure. Thus the elements approach is a valid and defensible one as long as the approach taken in the text is sufficiently global. That is, it should not be allowed to degenerate into a collection of apparently unrelated exercises, but rather provide an integrated approach.
Another area in which the author has found existing texts (and Machine Elements courses) to be deficient is the lack of connection made between the dynamics of a system and the stress analysis of that system. Typically, these texts present their machine elements with (magically) predefined forces on them. The student is then shown how to determine the stresses and deflections caused by those forces. In real machine design, the forces are not always predefined and can, in large part, be due to the accelerations of the masses of the moving parts. However, the masses cannot be accurately determined until the geometry is defined and a stress analysis done to determine the strength of the assumed part. Thus an impasse exists that is broken only by iteration, i.e., assume a part geometry and define its geometric and mass properties, calculate the dynamic loads due in part to the material and geometry of the part. Then calculate the stresses and deflections resulting from those forces, find out it fails, redesign, and repeat.
An Integrated Approach
The text is divided into two parts. The first part presents the fundamentals of stress, strain, deflection, materials properties, failure theories, fatigue phenomena, fracture mechanics, FEA, etc.
These theoretical aspects are presented in similar fashion to other texts. The second part presents treatments of specific, common design elements used as examples of applications of the theory but also attempts to avoid presenting a string of disparate topics in favor of an integrated approach that ties the various topics together via case studies.
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Most Elements texts contain many more topics and more content than can possibly be covered in a one-semester course. Before writing the first edition of this book, a questionnaire was sent to 200 U.S. university instructors of the Elements course to solicit their opinions on the relative importance and desirability of the typical set of topics in an Elements text. With each revision to second , third, and fourth editions, users were again surveyed to determine what should be changed or added. The responses were analyzed and used to influence the structure and content of this book in all editions. One of the strongest desires originally expressed by the respondents was for case studies that present realistic design problems.
We have attempted to accomplish this goal by structuring the text around a series of ten case studies. These case studies present different aspects of the same design problem in successive chapters, for example, defining the static or dynamic loads on the device in Chapter 3, calculating the stresses due to the static loads in Chapter 4, and applying the appropriate failure theory to determine its safety factor in Chapter 5. Later chapters present more complex case studies, with more design content. The case study in Chapter 6 on fatigue design is one such example a real problem taken from the author’s consulting practice. Chapter 8 presents FEA analyses of several of these case studies and compares those results to the classical solutions done in prior chapters.
The case studies provide a series of machine design projects throughout the book that contain various combinations of the elements normally dealt with in this type of text. The assemblies contain some collection of elements such as links subjected to combined axial and bending loads, column members, shafts in combined bending and torsion, gearsets under alternating loads, return springs, fasteners under fatigue loading, rolling element bearings, etc. This integrated approach has several advantages. It presents the student with a generic design problem in context rather than as a set of disparate, unrelated entities. The student can then see the interrelation-ships and the rationales for the design decisions that affect the individual elements. These more comprehensive case studies are in Part II of the text. The case studies in Part I are more limited in scope and directed to the engineering mechanics topics of the chapter. In addition to the case studies, each chapter has a selection of worked-out examples to reinforce particular topics.
Chapter 9, Design Case Studies, is devoted to the setup of three design case studies that are used in the following chapters to reinforce the concepts behind the design and analysis of shafts, springs, gears, fasteners, etc. Not all aspects of these design case studies are addressed as worked-out examples since another purpose is to provide material for student-project assignments. The author has used these case study topics as multi-week or term-long project assignments for groups or individual students with good success. Assigning open-ended project assignments serves to reinforce the design and analysis aspects of the course much better than set-piece homework assignments.
Problem Sets
Most of the 790 problem sets (590, or 75%) are independent within a chapter, responding to requests by users of the first edition to decouple them. The other 25% of the problem sets are still built upon in succeeding chapters. These linked problems have the same dash number in each chapter and their problem number is boldface to indicate their commonality among chapters. For example, Problem 3-4 asks for a static force analysis of a trailer hitch; Problem 4-4
requests a stress analysis of the same hitch based on the forces calculated in Problem 3-4; Problem 5-4 asks for the static safety factor for the hitch using the stresses calculated in Problem 4-4; Problem 6-4 requests a fatigue-failure analysis of the same hitch, and Problem 7-4 requires a surface stress analysis. The same trailer hitch is used as an FEA case study in Chapter 8. Thus, the complexity of the underlying design problem is unfolded as new topics are introduced. An
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instructor who wishes to use this approach can assign problems with the same dash number in succeeding chapters. If one does not want to assign an earlier problem on which a later one is based, the solution manual data from the earlier problem can be provided to the students. Instructors who do not like interlinked problems can avoid them entirely and select from the 590 problems with nonbold problem numbers that are independent within their chapters.
Text Arrangement
Chapter 1 provides an introduction to the design process, problem formulation, safety factors, and units. Material properties are reviewed in Chapter 2 since even the student who has had a first course in material science or metallurgy typically has but a superficial understanding of the wide spectrum of engineering material properties needed for machine design. Chapter 3 presents a review of static and dynamic loading analysis, including beam, vibration, and impact loading, and sets up a series of case studies that are used in later chapters to illustrate the stress and deflection analysis topics with some continuity.
The Design of Machine Elements course, at its core, is really an intermediate-level, applied stress-analysis course. Accordingly, a review of the fundamentals of stress and deflection analysis is presented in Chapter 4. Static failure theories are presented in detail in Chapter 5 since the students have typically not yet fully digested these concepts from their first stress-analysis course.
Fracture-mechanics analysis for static loads is also introduced.
The Elements course is typically the student’s first exposure to fatigue analysis since most introductory stress-analysis courses deal only with statically loaded problems. Accordingly, fatigue-failure theory is presented at length in Chapter 6 with the emphasis on stress-life approaches to high-cycle fatigue design, which is commonly used in the design of rotating machinery. Fracture-mechanics theory is further discussed with regard to crack propagation under cyclic loading. Strain-based methods for low-cycle fatigue analysis are not presented but their application and purpose are introduced to the reader and bibliographic references are provided for further study. Residual stresses are also addressed. Chapter 7 presents a thorough discussion of the phenomena of wear mechanisms, surface contact stresses, and surface fatigue.
Chapter 8 provides an introduction to Finite Element Analysis (FEA). Many instructors are using the machine elements course to introduce students to FEA as well as to instruct them in the techniques of machine design. The material presented in Chapter 8 is not intended as a substitute for education in FEA theory. That material is available in many other textbooks devoted to that subject and the student is urged to become familiar with FEA theory through coursework or self-study. Instead Chapter 8 presents proper techniques for the application of FEA to practical machine design problems. Issues of element selection, mesh refinement, and the definition of proper boundary conditions are developed in some detail. These issues are not usually addressed in books on FEA theory. Many engineers in training today will, in their professional practice, use CAD solid modeling software and commercial finite element analysis code. It is important that they have some knowledge of the limitations and proper application of those tools.
This chapter can be taken up earlier in the course if desired, especially if the students are expected to use FEA to solve assigned tasks. It is relatively independent of the other chapters. Many of various chapters’ problem assignments have Solidworks models of their geometry provided on the CD-ROM.
These eight chapters comprise Part I of the text and lay the analytical foundation needed for design of machine elements. They are arranged to be taken up in the order presented and build upon each other with the exception of Chapter 8 on FEA.
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Part II of the text presents the design of machine elements in context as parts of a whole machine. The chapters in Part II are essentially independent of one another and can be taken (or skipped) in any order that the instructor desires (except that Chapter 12 on spur gears should be studied before Chapter 13 on helical, bevel, and worm gears). It is unlikely that all topics in the book can be covered in a one-term or one semester course. Uncovered chapters will still serve as a reference for engineers in their professional practice.
Chapter 9 presents a set of design case studies to be used as assignments and as example case studies in the following chapters and also provides a set of suggested design project assignments in addition to the detailed case studies as described above. Chapter 10 investigates shaft design using the fatigue-analysis techniques developed in Chapter 6. Chapter 11 discusses fluid-film and rolling-element bearing theory and application using the theory developed in Chapter 7. Chapter 12 gives a thorough introduction to the kinematics, design and stress analysis of spur gears using the latest AGMA recommended procedures. Chapter 13 extends gear design to helical, bevel, and worm gearing. Chapter 14 covers spring design including helical compression, extension and torsion springs, as well as a thorough treatment of Belleville springs. Chapter 15
deals with screws and fasteners including power screws and preloaded fasteners. Chapter 16
presents an up-to-date treatment of the design of weldments for both static and dynamic loading. Chapter 17 presents an introduction to the design and specification of disk and drum clutches and brakes. The appendices contain material-strength data, beam tables, and stress-concentration factors, as well as answers to selected problems.
Supplements
A Solutions Manual is available to instructors from the publisher and PowerPoint slides of all figures and tables in the text are available on the publisher’s website (password protected) at:
http://www.pearsonhighered.com/
To download these resources, choose the Instructor Support tab to register as an instructor and follow instructions on the site to obtain the resources provided. Mathcad files for all the problem solutions are available with the solutions manual. This computerized approach to problem solutions has significant advantages to the instructor who can easily change any assigned problem’s data and instantly solve it. Thus an essentially infinite supply of problem sets is available, going far beyond those defined in the text. The instructor also can easily prepare and solve exam problems by changing data in the supplied files.
Anyone may download supplemental information about the author’s course organization and operation (syllabi, project assignments, etc.) from the author’s university web site at:
http://www.me.wpi.edu/People/Norton/design.html
As errata are discovered they will be posted on the author’s personal website at:
http://www.designofmachinery.com/MD/errata.html
Professors who adopt the book may register at the author’s personal website to obtain additional information relevant to the subject and the text and to download updated software (password protected). Go to:
http://www.designofmachinery.com/registered/professor.html
Anyone who purchases the book may register at the author’s personal website to request updated software for the current edition (password protected). Go to:
http://www.designofmachinery.com/registered/student.html
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Acknowledgments
The author expresses his sincere appreciation to all those who reviewed the first edition of the text in various stages of development including Professors J. E. Beard, Michigan Tech; J. M.
Henderson, U. California, Davis; L. R. Koval, U. Missouri, Rolla; S. N. Kramer, U. Toledo; L. D. Mitchell, Virginia Polytechnic; G. R. Pennock, Purdue; D. A. Wilson, Tennessee Tech; Mr.
John Lothrop; and Professor J. Ari-Gur, Western Michigan University, who also taught from a class-test version of the book. Robert Herrmann (WPI-ME ‘94) provided some problems and Charles Gillis (WPI-ME ‘96) solved most of the problem sets for the first edition.
Professors John R. Steffen of Valparaiso University, R. Jay Conant of Montana State, Norman E. Dowling of Virginia Polytechnic, and Francis E. Kennedy of Dartmouth made many useful suggestions for improvement and caught many errors. Special thanks go to Professor Hartley T. Grandin of WPI, who provided much encouragement and many good suggestions and ideas throughout the book’s gestation, and also taught from various class-test versions.
Three former and the current Prentice Hall editors deserve special mention for their efforts in developing this book: Doug Humphrey, who wouldn’t take no for an answer in persuading me to write it, Bill Stenquist, who usually said yes to my requests and expertly shepherded the book through to completion in its first edition, and Eric Svendsen who helped get the third edition into print and added value to the book. Tacy Quinn’s support has helped marshall the fourth edition into print.
Since the book’s first printing in 1995, several users have kindly pointed out errors and suggested improvements. My thanks go to Professors R. Boudreau of U. Moncton, Canada, V.
Glozman of Cal Poly Pomona, John Steele of Colorado School of Mines, Burford J. Furman of San Jose State University, and Michael Ward of California State University, Chico.
Several other faculty have been kind enough to point out errors and offer constructive criticisms and suggestions for improvement in the later editions. Notable among these are: Professors Cosme Furlong of Worcester Polytechnic Institute, Joseph Rencis of University of Arkansas, Annie Ross of Universite de Moncton, Andrew Ruina of Cornell University, Douglas Walcerz of York College, and Thomas Dresner of Mountain City, CA.
Dr. Duane Miller of Lincoln Electric Company provided invaluable help with Chapter 16
on weldments and reviewed several drafts. Professor Stephen Covey of St. Cloud State University, and engineers Gregory Aviza and Charles Gillis of P&G Gillette also provided valuable feed-back on the weldment chapter. Professor Robert Cornwell of Seattle University reviewed the discussion in Chapter 15 of his new method for the calculation of bolted joint stiffness and his method for computing stress concentration in rectangular wire springs discussed in Chapter 14.
Professors Fabio Marcelo Peña Bustos of Universidad Autónoma de Manizales, Caldas, Colombia, and Juan L. Balsevich-Prieto of Universidad Católica Nuestra Señora de la Asunción, Asunción, Paraguay, were kind enough to point out errata in the Spanish translation.
Special thanks are due to William Jolley of The Gillette Company who created the FEA models for the examples and reviewed Chapter 8, and to Edwin Ryan, retired Vice President of Engineering at Gillette, who provided invaluable support. Donald A. Jacques of the UTC Fuel Cells division of the United Technologies Company also reviewed Chapter 8 on Finite Element Analysis and made many useful suggestions. Professor Eben C. Cobb of Worcester Polytechnic Institute and his student Thomas Watson created the Solidworks models of many problem assignments and case studies and solved the FEA for the case studies that are on the CD-ROM.
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Thanks are due several people who responded to surveys for the fourth edition and made many good suggestions: Kenneth R. Halliday of Ohio State University, Mohamed B. Trabia of University of Nevada Los Vegas, H. J. Summer III of Penn State University, Rajeev Madhavan Nair of Iowas State University, Ali P. Gordon of University of Central Florida, Robert Jackson of Auburn University, Cara Coad of Colorado School of Mines, Burford J. Furman of San Jose State University, Steven J. Covey of St. Cloud State University, Nathan Crane of University of Central Florida, César Augusto Álvarez Vargas of Universidad Autonoma de Manizales, Caldas, Colombia, Naser Nawayseh of Dhofar University, Oman, Hodge E. Jenkins of Mercer University, John Lee of San Jose State University, Mahmoud Kadkhodaei of Isfahan University of Technology, Steve Searcy of Texas A&M University, Yesh P. Singh of University of Texas at San Antonio, and Osornio C. Cuitláhuac of Universidad Iberoamericana Santa Fe, Mexico.
The author is greatly indebted to Thomas A. Cook, Professor Emeritus, Mercer University, who did the Solutions Manual for this book, updated the Mathcad examples, and contributed most of the new problem sets for this edition. Thanks also to Dr. Adriana Hera of Worcester Polytechnic Institute who updated the MATLAB and Excel models of all the examples and case studies and thoroughly vetted their correctness.
Finally, Nancy Norton, my infinitely patient wife for the past fifty years, deserves renewed kudos for her unfailing support and encouragement during many summers of “book widowhood.”
I could not have done it without her.
Every effort has been made to eliminate errors from this text. Any that remain are the Robert L. Norton
author’s responsibility. He will greatly appreciate being informed of any errors that still remain Mattapoisett, Mass.
so they can be corrected in future printings. An e-mail to norton@wpi.edu will be sufficient.
August 1, 2009
P a r t
I
FUNDAMENTALS
1