An Introduction to Mechanical Engineering By Jonathan Wickert Kemper Lewis

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An Introduction to Mechanical Engineering By Jonathan Wickert Kemper Lewis

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Contents

Student’s Preface xi
Instructor’s Preface xiii
About the Authors xxi
CHAPTER 1 THE MECHANICAL ENGINEERING PROFESSION 1
1.1 Overview 1
The Elements of Mechanical Engineering 1
1.2 What Is Engineering? 4
1.3 Who Are Mechanical Engineers? 10
Mechanical Engineering’s Top Ten Achievements 12
1.4 Career Paths 22
1.5 Typical Program of Study 24
Summary 28
Self-Study and Review 28
Problems 29
References 31
CHAPTER 2 MECHANICAL DESIGN 33
2.1 Overview 33
2.2 The Design Process 37
Requirements Development 41
Conceptual Design 42
Detailed Design 43
Production 47
2.3 Manufacturing Processes 50
2.4 Case Study in Conceptual Design:
Mousetrap-Powered Vehicles 57
First Concept: String and Lever Arm 58
Second Concept: Compound Geartrain 59
Third Concept: Sector-Shaped Gear 61
2.5 Case Study in Urban Power Infrastructures 62
Requirements Development 62
Conceptual Design 63
Detailed Design 65
2.6 Case Study: Computer-Aided Design:
Noninvasive Medical Imaging 66
Summary 70
Self-Study and Review 71
Problems 72
References 76
CHAPTER 3 TECHNICAL PROBLEM-SOLVING AND COMMUNICATION
SKILLS 77
3.1 Overview 77
3.2 General Technical Problem-Solving Approach 82
3.3 Unit Systems and Conversions 84
Base and Derived Units 84
International System of Units 84
United States Customary System of Units 88
Converting Between the SI and USCS 91
3.4 Signifi cant Digits 96
3.5 Dimensional Consistency 98
3.6 Estimation in Engineering 107
3.7 Communication Skills in Engineering 112
Written Communication 113
Graphical Communication 115
Technical Presentations 116
Summary 120
Self-Study and Review 120
Problems 121
References 128
CHAPTER 4 FORCES IN STRUCTURES AND MACHINES 129
4.1 Overview 129
4.2 Forces in Rectangular and Polar Forms 131
Rectangular Components 132
Polar Components 133
4.3 Resultant of Several Forces 134
Vector Algebra Method 135
Vector Polygon Method 136
4.4 Moment of a Force 140
Perpendicular Lever Arm Method 140
Moment Components Method 142
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Contents vii
4.5 Equilibrium of Forces and Moments 148
Particles and Rigid Bodies 148
Free Body Diagrams 150
4.6 Design Application: Rolling-Element Bearings 158
Summary 166
Self-Study and Review 167
Problems 168
References 182
CHAPTER 5 MATERIALS AND STRESSES 183
5.1 Overview 183
5.2 Tension and Compression 185
5.3 Material Response 193
5.4 Shear 205
5.5 Engineering Materials 210
Metals and Their Alloys 211
Ceramics 212
Polymers 213
Composite Materials 214
5.6 Factor of Safety 218
Summary 222
Self-Study and Review 224
Problems 225
References 237
CHAPTER 6 FLUIDS ENGINEERING 238
6.1 Overview 238
6.2 Properties of Fluids 240
6.3 Pressure and Buoyancy Force 248
6.4 Laminar and Turbulent Fluid Flows 255
6.5 Fluid Flow in Pipes 259
6.6 Drag Force 266
6.7 Lift Force 275
Summary 281
Self-Study and Review 282
Problems 283
References 290
CHAPTER 7 THERMAL AND ENERGY SYSTEMS 291
7.1 Overview 291
7.2 Mechanical Energy, Work, and Power 293
Gravitational Potential Energy 293
Elastic Potential Energy 294
Kinetic Energy 294
Work of a Force 295
Power 295
7.3 Heat as Energy in Transit 300
Heating Value 300
Specifi c Heat 302
Transfer of Heat 304
7.4 Energy Conservation and Conversion 313
7.5 Heat Engines and Effi ciency 318
7.6 Case Study 1: Internal-Combustion Engines 323
Four-Stroke Engine Cycle 325
Two-Stroke Engine Cycle 328
7.7 Case Study 2: Electrical Power Generation 330
7.8 Case Study 3: Jet Engines 339
Summary 342
Self-Study and Review 343
Problems 344
References 350
CHAPTER 8 MOTION AND POWER TRANSMISSION 351
8.1 Overview 351
8.2 Rotational Motion 353
Angular Velocity 353
Rotational Work and Power 355
8.3 Design Application: Gears 359
Spur Gears 360
Rack and Pinion 364
Bevel Gears 364
Helical Gears 364
Worm Gearsets 367
8.4 Speed, Torque, and Power in Gearsets 369
Speed 370
Torque 371
Power 372
8.5 Simple and Compound Geartrains 373
Simple Geartrain 373
Compound Geartrain 374
8.6 Design Application: Belt and Chain Drives 380
8.7 Planetary Geartrains 386
Summary 394
Self-Study and Review 396
Problems 396
References 407
APPENDIX A GREEK ALPHABET 409
APPENDIX B TRIGONOMETRY REVIEW 410
B.1 Degrees and Radians 410
B.2 Right Triangles 410
B.3 Identities 411
B.4 Oblique Triangles 412
INDEX 413

Student’s Preface

PURPOSE
This textbook will introduce you to the ever-emerging fi eld of mechanical
engineering and help you appreciate how engineers design the hardware that
builds and improves societies all around the world. As the title implies, this
textbook is neither an encyclopedia nor a comprehensive treatment of the
discipline. Such a task is impossible for a single textbook, and, regardless, our
perspective is that the traditional four-year engineering curriculum is just one
of many steps taken during a lifelong education. By reading this textbook,
you will discover the “forest” of mechanical engineering by examining a few
of its “trees,” and along the way you will be exposed to some interesting and
practical elements of the profession called mechanical engineering.
APPROACH AND CONTENT
This textbook is intended for students who are in the fi rst or second years
of a typical college or university program in mechanical engineering or a
closely related fi eld. Throughout the following chapters, we have attempted
to balance the treatments of technical problem-solving skills, design,
engineering analysis, and modern technology. The presentation begins with
a narrative description of mechanical engineers, what they do, and the impact
they can have (Chapter 1). Seven “elements” of mechanical engineering are
emphasized subsequently in Chapter 2 (Mechanical Design), Chapter 3
(Professional Practice), Chapter 4 (Forces in Structures and Machines),
Chapter 5 (Materials and Stresses), Chapter 6 (Fluids Engineering),
Chapter 7 (Thermal and Energy Systems), and Chapter 8 (Motion and Power
Transmission). Some of the applications that you will encounter along the
way include sustainable urban infrastructures, virtual and rapid prototyping,
nanomachines, internal combustion engines, robotics, sports technology,
magnetic resonance imaging, advanced materials, jet engines, micro-fl uidic
devices, automatic transmissions, and renewable energy.
What should you be able to learn from this textbook? First and
foremost, you will discover who mechanical engineers are, what they do,
and what technical, social, and environmental challenges they solve with
the technol ogies they create. Section 1.3 details a “top ten” list of the
profession’s achievements. By looking at this list, you will recognize how
the profession has contributed to your day-to-day life and society around
the world in general. Second, you will fi nd that engineering is a practical
endeavor with the objective of designing things that work, that are costeffective
to manufacture, that are safe to use, and that are responsible in terms
of their environmental impact. Third, you will learn some of the calculations,
estimates, and approximations that mechanical engineers can perform as they
solve technical problems and communicate their results. To accomplish their
jobs better and faster, mechanical engineers combine mathematics, science,
computer-aided engineering tools, experience, and hands-on skills.
You will not be an expert in mechanical engineering after having read
this textbook, but that is not our intention, and it should not be yours. If
our objective has been met, however, you will set in place a solid foundation
of problem-solving, design, and analysis skills, and those just might form
the basis for your own future contributions to the mechanical engineering
profession.

Instructor’s Preface

APPROACH
This textbook is intended for a course that provides an introduction to
mechanical engineering during either the freshman or sophomore years.
Over the past decade, many colleges and universities have taken a fresh look
at their engineering curricula with the objective of positioning engineering
content earlier in their programs. Particularly for the freshman year, the
formats vary widely and can include seminars on “who are mechanical
engineers” and “what do they do,” innovative design experiences, problemsolving
skills, basic engineering analysis, and case studies. Courses at the
sophomore level often emphasize design projects, exposure to computeraided
engineering, principles of engineering science, and a healthy dose of
mechanical engineering hardware.
Core engineering-science courses (for example, strength of materials,
thermodynamics, fl uid mechanics, and dynamics) have evolved since the post–
World War II era into their present, relatively mature, states. On the other hand,
little if any standardization exists among introductory mechanical engineering
courses. With limited discipline-specifi c instructional materials available for
such courses, we believe that an important opportunity remains for attracting
students, exciting them with a view of what to expect later in their program of
study and in their future careers, and providing them with a foundation of sound
engineering analysis, technical problem-solving, and design skills.
OBJECTIVES
While developing the third edition of this textbook, our objective has been
to provide a resource that others can draw upon when teaching introductory
mechanical engineering to fi rst-year and second-year students. We expect
that most such courses would encompass the bulk of material presented in
Chapter 1 (The Mechanical Engineering Profession), Chapter 2 (Mechanical
Design), and Chapter 3 (Technical Problem Solving and Communication
Skills). Based on the level and contact hours of their particular courses,
instructors can select additional topics from Chapter 4 (Forces in Structures
and Machines), Chapter 5 (Materials and Stresses), Chapter 6 (Fluids
Engineering), Chapter 7 (Thermal and Energy Systems), and Chapter 8
(Motion and Power Transmission). For instance, Section 5.5 on materials
selection is largely self-contained, and it provides an introductory-level
student with an overview of the different classes of engineering materials.
Similarly, the descriptions in Sections 7.6 through 7.8 of internal-combustion
engines, electrical power plants, and jet engines are expository in nature,

and that material can be incorporated in case studies to demonstrate the
operation of some important mechanical engineering hardware. Rollingcontact
bearings, gears, and belt and chain drives are similarly discussed in
Sections 4.6, 8.3, and 8.6.
This textbook refl ects our experiences and philosophy for introducing
students to the vocabulary, skills, applications, and excitement of the mechanical
engineering profession. Our writing has been motivated in part by teaching
introductory mechanical engineering courses at our respective universities.
Collectively, these courses have included lectures, computer-aided design and
manufacturing projects, product dissection laboratories (an example of which
is discussed in Section 2.1), and team design projects (examples of which are
outlined in Sections 2.4 and 2.5 in the context of design conceptualization).
A number of vignettes and case studies are also discussed to demonstrate for
students the realism of what they are learning, including the “top ten” list of
achievements developed by the American Society of Mechanical Engineers
(Section 1.3), the fourteen “grand challenges” from the National Academy of
Engineering (NAE) (Section 2.1), design innovation and patents (Section 2.2),
urban power infrastructures (Section 2.5), integrated computer-aided
engineering (Section 2.6), the loss of the Mars Climate Orbiter spacecraft and
the refueling error on Air Canada Flight 143 (Section 3.1), the Deepwater
Horizon oil spill disaster (Section 3.6), the Challenger disaster (Section 3.7),
the Kansas City Hyatt Hotel disaster (Section 4.5), the design of Masdar City
(Section 5.2), the design of advanced materials (Section 5.5), microfl uidic
devices (Section 6.2), blood fl ow in the human body (Section 6.5), sports
technology (Sections 6.6 and 6.7), renewable energies (Section 7.5), internal
combustion engines (Section 7.6), solar power generation (Section 7.7), and
nanomachines (Section 8.3).
The “Focus on . . . ” boxes in each chapter are used to highlight some
of these interesting topics and other emerging concepts in mechanical
engineering.
CONTENT
We certainly have not intended this textbook to be an exhaustive treatment
of Mechanical Engineering, and we trust that it will not be read in that light.
Quite the contrary: In teaching fi rst-year and second-year students, we are
ever conscious of the mantra that “less really is more.” To the extent possible,
we have resisted the urge to add just one more section on a particular subject,
and we have tried to keep the material manageable and engaging from the
reader’s perspective. Indeed, many topics that are important for mechanical
engineers to know are simply not included here; this is done intentionally (or,
admittedly, by our own oversight). We are confi dent, however, that students
will be exposed to those otherwise omitted subjects in due course throughout
the remainder of their engineering curricula.
In Chapters 2 through 8, we have selected a subset of mechanical
engineering “elements” that can be suffi ciently covered for early students
to develop useful design, technical problem-solving, and analysis skills.
Instructor’s Preface xv
The coverage has been chosen to facilitate the textbook’s use within the
constraints of courses having various formats. While there is more material
here than can be comfortably covered in a single semester, instructors should
fi nd a reasonable menu from which to choose. In particular, we have selected
content that we have found to
1. Match the background, maturity, and interests of students early in their
study of engineering
2. Expose students to the signifi cance of mechanical design principles in
the development of innovative solutions to technical challenges that
face our global societies
3. Help students think critically and learn good problem-solving skills,
particularly with respect to formulating sound assumptions, making
order-of-magnitude approximations, performing double-checks, and
bookkeeping proper units
4. Convey aspects of mechanical engineering science and empiricism that
can be applied at the freshman and sophomore levels
5. Expose students to a wide range of hardware, innovative designs,
engineering technology, and the hands-on nature of mechanical
engineering
6. Generate excitement through applications encompassing urban
infrastructure development, nanomachines, aircraft, space fl ight,
robotics, engines, consumer products, transmissions, renewable energy
generation, and more
To the extent possible at the freshman and sophomore levels, the exposition,
examples, and homework problems have been drawn from realistic
applications. You will fi nd no masses on inclined planes or block-and-tackle
systems in this textbook. Because we fi nd engineering to be a visual and
graphical activity, we have placed particular emphasis on the quality and
breadth of the nearly three hundred photographs and illustrations, many
of which were provided by our colleagues in industry, federal agencies, and
academe. Our view has been to leverage that realism and motivate students
through interesting examples that offer a glimpse of what they will be able to
study in later courses and, subsequently, practice in their own careers.
NEW IN THE THIRD EDITION
In preparing this third edition, we have made many of the types of changes
that one would expect: Sections have been rewritten and reorganized, new
material has been added, some material has been removed, new examples
problems have been created, and small mistakes have been corrected. Almost
90 new homework problems have been developed and over 60 new fi gures
have been included.
We have attempted to remain faithful to the philosophy of the fi rst
two editions by emphasizing the importance of the mechanical engineering
profession to solving global problems, including new information in
xvi Instructor’s Preface
Chapter 1 on recent professional trends, technology development,
mechanical engineering career paths, and knowledge areas. Also, in
Chapter 1, we introduce an updated fi gure illustrating the organization
of mechanical engineering topics both in this edition and in a typical
mechanical engineering curriculum. This fi gure is used in each chapter to
depict graphically how the chapter’s content fi ts into the overall study of
mechanical engineering.
A signifi cant change in this edition is the shift of the chapter on
Mechanical Design to Chapter 2, refl ecting the growing importance of sound
design principles in the development of engineered products and systems.
In Chapter 2, new material is included on design innovation, the National
Academy of Engineering Grand Challenges, design processes, customized
production, and a case study on designing urban power infrastructures. The
following new material has been integrated into the remaining chapters:
technical problem solving, written and graphical communication, and
signifi cant fi gures (Chapter 3); Newton’s laws of motion (Chapter 4); sports
technology (Chapter 6); updated notation and a solar power design example
(Chapter 7).
Each chapter example has been placed in an improved pedagogical format
comprising the problem’s statement, approach, solution, and discussion. In
particular, the discussion portion is intended to highlight why the numerical
answer is interesting or why it makes intuitive sense. Symbolic equations are
written alongside the numerical calculations. Throughout the textbook, the
dimensions appearing in these calculations are explicitly manipulated and
canceled in order to reinforce good technical problem-solving skills.
The “Focus on . . . ” boxes contain topical material, either conceptual
or applied, that broadens the textbook’s coverage without detracting from
its fl ow. New topics in the “Focus on . . . ” boxes include the dynamic fi eld
of mechanical engineering; product archaeology; engineering estimations
using the Deepwater Horizon disaster; ineffective communication practices;
the design of sustainable cities; advanced material technology; microfl uidic
devices; fluid flow across large surfaces; global energy consumption;
renewable energy; design, policy, and innovation; nanomachines; and clean
energy vehicles.
As was the intent with the fi rst two editions, we have attempted to
make the third edition’s content readily accessible to any student having
a conventional secondary school background in mathematics and physics.
We have not relied on any mathematics beyond algebra, geometry, and
trigonometry (which is reviewed in Appendix B), and in particular, we have
not used any cross-products, integrals, derivatives, or differential equations.
Consistent with that view, we have intentionally not included a chapter
that addresses the subjects of dynamics, dynamic systems, and mechanical
vibration. We remain focused on the earliest engineering students, many
of whom will be studying calculus concurrently. Keeping those students in
mind, we feel that the added mathematical complexity would detract from
this textbook’s overall mission.
SUPPLEMENTS
Supplements for instructors are available on the Instructor Companion Web
site at www.cengagebrain.com.
• Instructor Solutions Manual (Completely revised)
• PowerPoint Presentations (Completely revised; all the photos, fi gures,
and tables from the textbook)
• LectureBuilder PowerPoint Presentations (New: all the equations and
examples from the textbook)
COURSEMATE
CourseMate from Cengage Learning offers student book-specifi c interactive
learning tools at an incredible value. Each CourseMate Web site includes an
e-book and interactive learning tools. To access additional course materials
(including CourseMate) please visit www.cengagebrain.com
At the cengagebrain.com home page, search for the ISBN of your title
(from the back cover of your book) using the search box at the top of the page.
This will take you to the product page where these resources can be found.
ACKNOWLEDGMENTS
It would have been impossible to develop the three editions of this textbook
without the contributions of many people and organizations, and at the
outset, we would like to express our appreciation to them. Generous support
was provided by the Marsha and Philip Dowd Faculty Fellowship, which
encourages educational initiatives in engineering, and by the National Science
Foundation for the product archaeology initiatives in Chapter 2. Adriana
Moscatelli, Jared Schneider, Katie Minardo, and Stacy Mitchell, helped to
get this project off the ground by drafting many of the illustrations. The
expert assistance provided by Ms. Jean Stiles in proofreading the textbook and
preparing the fi rst version Instructor’s Solutions Manual was indispensable. We
very much appreciate the many contributions she made.
Our colleagues, graduate students, and teaching assistants at Carnegie
Mellon University, Iowa State University, and the University at Buffalo—
SUNY provided many valuable comments and suggestions as we wrote the
editions. We would specifi cally like to thank Adnan Akay, Jack Beuth, Paul
Steif, Allen Robinson, Shelley Anna, Yoed Rabin, Burak Ozdoganlar, Parker
Lin, Elizabeth Ervin, Venkataraman Kartik, Matthew Brake, John Collinger,
Annie Tangpong, Matthew Iannacci, Erich Devendorf, Phil Cormier, Aziz
Naim, David Van Horn, Brian Literman, and Vishwa Kalyanasundaram for
their comments. We are likewise indebted to the students in our courses:
Fundamentals of Mechanical Engineering (Carnegie Mellon), Introduction
to Mechanical Engineering Practice (University at Buffalo—SUNY),
and Design Process and Methods (University at Buffalo—SUNY). Their
collective interest, feedback, and enthusiasm have always provided muchneeded
forward momentum. Joe Elliot and John Wiss kindly offered the
engine dynamometer and cylinder pressure data to frame the discussion
of internal-combustion engines in Chapter 7. Solutions to many of the
homework problems were drafted by Brad Lisien and Albert Costa and we
appreciate their hard work and conscientious effort. We are also grateful to
Philip Odonkor who drafted additional homework problems and solutions,
and conducted research for the “Focus On . . . ” sections in the third edition.
In addition, the following reviewers of the fi rst, second, and third editions
were kind enough to let us benefi t from their perspectives and teaching
experience: Terry Berreen, Monash University; John R. Biddle, California
State Polytechnic University at Pomona; Terry Brown, University of
Technology (Sydney); Peter Burban, Cedarville University; David F. Chichka,
George Washington University; Scott Danielson, Arizona State University;
William Hallett, University of Ottawa; David W. Herrin, University of
Kentucky; Robert Hocken, University of North Carolina (at Charlotte);
Damir Juric, Georgia Institute of Technology; Bruce Karnopp, University of
Michigan; Kenneth A. Kline, Wayne State University; Pierre M. Larochelle,
Florida Institute of Technology; Steven Y. Liang, Georgia Institute of
Technology; Per Lundqvist, Royal Institute of Technology (Stockholm);
William E. Murphy, University of Kentucky; Petru Petrina, Cornell
University; Anthony Renshaw, Columbia University; Timothy W. Simpson,
Pennsylvania State University; K. Scott Smith, University of North Carolina
(at Charlotte); Michael M. Stanisic, University of Notre Dame; Gloria Starns,
Iowa State University; David J. Thum, California Polytechnic State University
(San Luis Obispo); and David A. Willis, Southern Methodist University. We
are grateful for their detailed comments and helpful suggestions.
On all counts, we have enjoyed interacting with the editorial staff at
Cengage Learning. Chris Shortt, the Publisher, and Randall Adams, the
Acquisitions Editor, are equally as committed to developing a high-quality
product as the original publishers of the fi rst edition. Hilda Gowans, Amy
Hill, and Kristiina Paul have all contributed to the on-going development
of the book, while Rose Kernan and her staff at RPK Editorial Services
continue to combine skill and professionalism with a keen eye for detail in
the production of the book. To all, we express our thanks for a job well done.
Colleagues at the following industrial, academic, and governmental
organizations were remarkably helpful and patient in providing us with
photographs, illustrations, and technical information: General Motors, Intel,
Fluent, General Electric, Enron Wind, Boston Gear, Mechanical Dynamics,
Caterpillar, NASA, NASA’s Glenn Research Center, W. M. Berg, FANUC
Robotics, the U.S. Bureau of Reclamation, Niagara Gear, Velocity11, Stratasys,
National Robotics Engineering Consortium, Lockheed-Martin, Algor, MTS
Systems, Westinghouse Electric, Timken, Sandia National Laboratories,
Hitachi Global Storage Technologies, Segway LLC, the U.S. Department
of Labor, and the U.S. Department of Energy. Sam Dedola and John Haury
of Medrad, Incorporated went the extra mile and developed numerous
illustrations for the discussion of computer-aided design in Section 2.6.
We’ve surely not listed everyone who has helped us with this endeavor, and
we apologize for any inadvertent omissions that we may have made.