Machine Design

Brief Contents PART I: FUNDAMENTALS

Introduction to Design

1.1 Design

Machine Design


1.2 A Design Process
1.3 Problem Formulation and Calculation

Definition Stage
Preliminary Design Stage
Detailed Design Stage
Documentation Stage


1.4 The Engineering Model

Estimation and First-Order Analysis
The Engineering Sketch


1.5 Computer-Aided Design and Engineering

Computer-Aided Design (CAD)
Computer-Aided Engineering (CAE)
Computational Accuracy


1.6 The Engineering Report
1.7 Factors of Safety and Design Codes

Factor of Safety
Choosing a Safety Factor
Design and Safety Codes


1.8 Statistical Considerations
1.9 Units
1.10 Summary
1.11 References
1.12 Web References
1.13 Bibliography
1.14 Problems


Materials and Processes

2.0 Introduction
2.1 Material-Property Definitions

The Tensile Test
Ductility and Brittleness
The Compression Test
The Bending Test
The Torsion Test
Fatigue Strength and Endurance Limit
Impact Resistance
Fracture Toughness
Creep and Temperature Effects


2.2 The Statistical Nature of Material Properties
2.3 Homogeneity and Isotropy
2.4 Hardness

Heat Treatment
Surface (Case) Hardening
Heat Treating Nonferrous Materials
Mechanical Forming and Hardening


2.5 Coatings and Surface Treatments

Galvanic Action
Electroplating
Electroless Plating
Anodizing
Plasma-Sprayed Coatings
Chemical Coatings


2.6 General Properties of Metals

Cast Iron
Cast Steels
Wrought Steels
Steel Numbering Systems
Aluminum
Titanium
Magnesium
Copper Alloys


2.7 General Properties of Nonmetals

Polymers
Ceramics
Composites


2.8 Selecting Materials
2.9 Summary
2.10 References
2.11 Web References
2.12 Bibliography
2.13 Problems


Kinematics and Load Determination

3.0 Introduction
3.1 Degree of Freedom
3.2 Mechanisms
3.3 Calculating Degree of Freedom (Mobility)
3.4 Common 1-DOF Mechanisms

Fourbar Linkage and the Grashof Condition
Sixbar Linkage
Cam and Follower


3.5 Analyzing Linkage Motion

Types of Motion
Complex Numbers as Vectors
The Vector Loop Equation


3.6 Analyzing the Fourbar Linkage

Solving for Position in the Fourbar Linkage
Solving for Velocity in the Fourbar Linkage
Angular Velocity Ratio and Mechanical Advantage
Solving for Acceleration in the Fourbar Linkage


3.7 Analyzing the Fourbar Crank-Slider

Solving for Position in the Fourbar Crank-Slider
Solving for Velocity in the Fourbar Crank-Slider
Solving for Acceleration in the Fourbar Crank-Slider
Other Linkages


3.8 Cam Design and Analysis

The Timing Diagram
The svaj Diagram
Polynomials for the Double-Dwell Case
Polynomials for the Single-Dwell Case
Pressure Angle
Radius of Curvature


3.9 Loading Classes For Force Analysis
3.10 Free-body Diagrams
3.11 Load Analysis

Three-Dimensional Analysis
Two-Dimensional Analysis
Static Load Analysis


3.12 Two-Dimensional, Static Loading Case Studies
3.13 Three-Dimensional, Static Loading Case Study
3.14 Dynamic Loading Case Study
3.15 Vibration Loading

Natural Frequency
Dynamic Forces


3.16 Impact Loading

Energy Method


3.17 Beam Loading

Shear and Moment
Singularity Functions
Superposition


3.18 Summary
3.19 References
3.20 Web References
3.21 Bibliography
3.22 Problems


Stress, Strain, and Deflection

4.0 Introduction
4.1 Stress
4.2 Strain
4.3 Principal Stresses
4.4 Plane Stress and Plane Strain

Plane Stress
Plane Strain


4.5 Mohr’s Circles
4.6 Applied Versus Principal Stresses
4.7 Axial Tension
4.8 Direct Shear Stress, Bearing Stress, and Tearout

Direct Shear
Direct Bearing
Tearout Failure


4.9 Beams and Bending Stresses

Beams in Pure Bending
Shear Due to Transverse Loading


4.10 Deflection in Beams

Deflection by Singularity Functions
Statically Indeterminate Beams


4.11 Castigliano’s Method

Deflection by Castigliano’s Method
Finding Redundant Reactions with Castigliano’s Method


4.12 Torsion
4.13 Combined Stresses
4.14 Spring Rates
4.15 Stress Concentration Stress Concentration Under Static Loading

Stress Concentration Under Dynamic Loading
Determining Geometric Stress-Concentration Factors
Designing to Avoid Stress Concentrations


4.16 Axial Compression - Columns

Slenderness Ratio
Short Columns
Long Columns
End Conditions
Intermediate Columns


4.17 Stresses in Cylinders

Thick-Walled Cylinders
Thin-Walled Cylinders


4.18 Case Studies in Static Stress and Deflection Analysis
4.19 Summary
4.20 References
4.21 Bibliography
4.22 Problems


Static Failure Theories

5.0 Introduction
5.1 Failure of Ductile Materials Under Static Loading

The von Mises-Hencky or Distortion-Energy Theory
The Maximum Shear-Stress Theory
The Maximum Normal-Stress Theory
Comparison of Experimental Data with Failure Theories


5.2 Failure of Brittle Materials Under Static Loading

Even and Uneven Materials
The Coulomb-Mohr Theory
The Modified-Mohr Theory


5.3 Fracture Mechanics

Fracture-Mechanics Theory
Fracture Toughness Kc


5.4 Using The Static Loading Failure Theories
5.5 Case Studies in Static Failure Analysis
5.6 Summary
5.7 References
5.8 Bibliography
5.9 Problems


Fatigue Failure Theories

6.0 Introduction

History of Fatigue Failure


6.1 Mechanism of Fatigue Failure

Crack Initiation Stage
Crack Propagation Stage
Fracture


6.2 Fatigue-Failure Models

Fatigue Regimes
The Stress-Life Approach 3
The Strain-Life Approach
The LEFM Approach


6.3 Machine-Design Considerations
6.4 Fatigue Loads

Rotating Machinery Loading
Service Equipment Loading


6.5 Measuring Fatigue Failure Criteria

Fully Reversed Stresses
Combined Mean and Alternating Stress
Fracture-Mechanics Criteria
Testing Actual Assemblies


6.6 Estimating Fatigue Failure Criteria

Estimating the Theoretical Fatigue Strength Sf ’ or Endurance Limit Se’
Correction Factors—Theoretical Fatigue Strength or Endurance Limit
Corrected Fatigue Strength Sf or Corrected Endurance Limit Se
Creating Estimated S-N Diagrams


6.7 Notches and Stress Concentrations

Notch Sensitivity


6.8 Residual Stresses
6.9 Designing for High-Cycle Fatigue
6.10 Designing for Fully Reversed Uniaxial Stresses

Design Steps for Fully Reversed Stresses with Uniaxial Loading


6.11 Designing for Fluctuating Uniaxial Stresses

Creating the Modified-Goodman Diagram
Applying Stress-Concentration Effects with Fluctuating Stresses
Determining the Safety Factor with Fluctuating Stresses
Design Steps for Fluctuating Stresses


6.12 Designing for Multiaxial Stresses in Fatigue

Frequency and Phase Relationships
Fully Reversed Simple Multiaxial Stresses
Fluctuating Simple Multiaxial Stresses
Complex Multiaxial Stresses


6.13 A General Approach to High-Cycle Fatigue Design
6.14 A Case Study in Fatigue Design
6.15 Summary
6.16 References
6.17 Bibliography
6.18 Problems


Surface Failure

7.0 Introduction
7.1 Surface Geometry
7.2 Mating Surfaces
7.3 Friction

Effect of Roughness on Friction
Effect of Velocity on Friction
Rolling Friction
Effect of Lubricant on Friction


7.4 Adhesive Wear

The Adhesive-Wear Coefficient


7.5 Abrasive Wear

Abrasive Materials
Abrasion-Resistant Materials


7.6 Corrosion Wear

Corrosion Fatigue
Fretting Corrosion


7.7 Surface Fatigue
7.8 Spherical Contact

Contact Pressure and Contact Patch in Spherical Contact
Static Stress Distributions in Spherical Contact


7.9 Cylindrical Contact

Contact Pressure and Contact Patch in Parallel Cylindrical Contact
Static Stress Distributions in Parallel Cylindrical Contact


7.10 General Contact

Contact Pressure and Contact Patch in General Contact
Stress Distributions in General Contact


7.11 Dynamic Contact Stresses

Effect of a Sliding Component on Contact Stresses


7.12 Surface Fatigue Failure Models—Dynamic Contact
7.13 Surface Fatigue Strength
7.14 Summary
7.15 References
7.16 Problems


Finite Element Analysis

8.0 Introduction

Stress and Strain Computation


8.1 Finite Element Method
8.2 Element Types

Element Dimension and Degree of Freedom (DOF)
Element Order
H-Elements Versus P-Elements
Element Aspect Ratio


8.3 Meshing

Mesh Density
Mesh Refinement
Convergence


8.4 Boundary Conditions
8.5 Applying Loads
8.6 Testing the Model (Verification)
8.7 Modal Analysis
8.8 Case Studies
8.9 Summary
8.10 References
8.11 Bibliography
8.12 Web Resources
8.13 Problems



PART II: MACHINE DESIGN

Design Case Studies

9.0 Introduction
9.1 Case Study 8—A Portable Air Compressor
9.2 Case Study 9—A Hay-Bale Lifter
9.3 Case Study 10—A Cam-Testing Machine
9.4 Summary
9.5 References
9.6 Design Projects


Shafts, Keys, and Couplings

10.0 Introduction
10.1 Shaft Loads
10.2 Attachments and Stress Concentrations
10.3 Shaft Materials
10.4 Shaft Power
10.5 Shaft Loads
10.6 Shaft Stresses
10.7 Shaft Failure in Combined Loading
10.8 Shaft Design

General Considerations
Design for Fully Reversed Bending and Steady Torsion
Design for Fluctuating Bending and Fluctuating Torsion


10.9 Shaft Deflection

Shafts as Beams
Shafts as Torsion Bars


10.10 Keys and Keyways

Parallel Keys
Tapered Keys
Woodruff Keys
Stresses in Keys
Key Materials
Key Design
Stress Concentrations in Keyways


10.11 Splines
10.12 Interference Fits

Stresses in Interference Fits
Stress Concentration in Interference Fits
Fretting Corrosion


10.13 Flywheel Design

Energy Variation in a Rotating System
Determining the Flywheel Inertia
Stresses in Flywheels
Failure Criteria


10.14 Critical Speeds of Shafts

Lateral Vibration of Shafts and Beams—Rayleigh’s Method
Shaft Whirl
Torsional Vibration
Two Disks on a Common Shaft
Multiple Disks on a Common Shaft
Controlling Torsional Vibrations


10.15 Couplings

Rigid Couplings
Compliant Couplings


10.16 Case Study 8B

Designing Driveshafts for a Portable Air Compressor


10.17 Summary
10.18 References
10.19 Problems


Bearings and Lubrication

11.0 Introduction

A Caveat


11.1 Lubricants
11.2 Viscosity
11.3 Types of Lubrication

Full-Film Lubrication
Boundary Lubrication


11.4 Material Combinations in Sliding Bearings
11.5 Hydrodynamic Lubrication Theory

Petroff’s Equation for No-Load Torque
Reynolds’ Equation for Eccentric Journal Bearings
Torque and Power Losses in Journal Bearings


11.6 Design of Hydrodynamic Bearings

Design Load Factor—The Ocvirk Number
Design Procedures


11.7 Nonconforming Contacts
11.8 Rolling-element Bearings

Comparison of Rolling and Sliding Bearings
Types of Rolling-Element Bearings


11.9 Failure of Rolling-element bearings
11.10 S election of Rolling-element bearings

Basic Dynamic Load Rating C
Modified Bearing Life Rating
Basic Static Load Rating C0
Combined Radial and Thrust Loads
Calculation Procedures


11.11 Bearing Mounting Details
11.12 Special Bearings
11.13 Case Study 10B
11.14 Summary

Important Equations Used in This Chapter


11.15 References
11.16 Problems


Spur Gears

12.0 Introduction
12.1 Gear Tooth Theory

The Fundamental Law of Gearing
The Involute Tooth Form
Pressure Angle
Gear Mesh Geometry
Rack and Pinion
Changing Center Distance
Backlash
Relative Tooth Motion


12.2 Gear Tooth Nomenclature
12.3 Interference and Undercutting

Unequal-Addendum Tooth Forms


12.4 Contact Ratio
12.5 Gear Trains

Simple Gear Trains
Compound Gear Trains
Reverted Compound Trains
Epicyclic or Planetary Gear Trains


12.6 Gear Manufacturing

Forming Gear Teeth
Machining
Roughing Processes
Finishing Processes
Gear Quality


12.7 Loading on Spur Gears
12.8 Stresses in Spur Gears

Bending Stresses
Surface Stresses


12.9 Gear Materials

Material Strengths
Bending-Fatigue Strengths for Gear Materials
Surface-Fatigue Strengths for Gear Materials


12.10 Lubrication of Gearing
12.11 Design of Spur Gears
12.12 Case Study 8C
12.13 Summary
12.14 References
12.15 Problems


Helical, Bevel, and Worm Gears

13.0 Introduction
13.1 Helical Gears

Helical Gear Geometry
Helical-Gear Forces
Virtual Number of Teeth
Contact Ratios
Stresses in Helical Gears


13.2 Bevel Gears

Bevel-Gear Geometry and Nomenclature
Bevel-Gear Mounting
Forces on Bevel Gears
Stresses in Bevel Gears


13.3 Wormsets

Materials for Wormsets
Lubrication in Wormsets
Forces in Wormsets
Wormset Geometry
Rating Methods
A Design Procedure for Wormsets


13.4 Case Study 9B
13.5 Summary
13.6 References
13.7 Problems


Spring Design

14.0 Introduction
14.1 Spring Rate
14.2 Spring Configurations
14.3 Spring Materials

Spring Wire
Flat Spring Stock


14.4 Helical Compression Springs

Spring Lengths
End Details
Active Coils
Spring Index
Spring Deflection
Spring Rate
Stresses in Helical Compression Spring Coils
Helical Coil Springs of Nonround Wire
Residual Stresses
Buckling of Compression Springs
Compression-Spring Surge
Allowable Strengths for Compression Springs
The Torsional-Shear S-N Diagram for Spring Wire
The Modified-Goodman Diagram for Spring Wire


14.5 Designing Helical Compression Springs for Static Loading
14.6 Designing Helical Compression Springs for Fatigue Loading
14.7 Helical Extension Springs

Active Coils in Extension Springs
Spring Rate of Extension Springs
Spring Index of Extension Springs
Coil Preload in Extension Springs
Deflection of Extension Springs
Coil Stresses in Extension Springs
End Stresses in Extension Springs
Surging in Extension Springs
Material Strengths for Extension Springs
Design of Helical Extension Springs


14.8 Helical Torsion Springs

Terminology for Torsion Springs
Number of Coils in Torsion Springs
Deflection of Torsion Springs
Spring Rate of Torsion Springs
Coil Closure
Coil Stresses in Torsion Springs
Material Parameters for Torsion Springs
Safety Factors for Torsion Springs
Designing Helical Torsion Springs


14.9 Belleville Spring Washers

Load-Deflection Function for Belleville Washers
Stresses in Belleville Washers
Static Loading of Belleville Washers
Dynamic Loading
Stacking Springs
Designing Belleville Springs


14.10 Case Study 10C
14.11 Summary
14.12 References
14.13 Problems


Screws and Fasteners

15.0 Introduction
15.1 Standard Thread Forms

Tensile Stress Area
Standard Thread Dimensions


15.2 Power Screws

Square, Acme, and Buttress Threads
Power Screw Application
Power Screw Force and Torque Analysis
Friction Coefficients
Self-Locking and Back-Driving of Power Screws
Screw Efficiency
Ball Screws


15.3 Stresses in Threads

Axial Stress
Shear Stress
Torsional Stress


15.4 Types of Screw Fasteners

Classification by Intended Use
Classification by Thread Type
Classification by Head Style
Nuts and Washers


15.5 Manufacturing Fasteners
15.6 Strengths of Standard Bolts and Machine Screws
15.7 Preloaded Fasteners in Tension

Preloaded Bolts Under Static Loading
Preloaded Bolts Under Dynamic Loading


15.8 Determining the Joint Stiffness Factor

Joints With Two Plates of the Same Material
Joints With Two Plates of Different Materials
Gasketed Joints


15.9 Controlling Preload

The Turn-of-the-Nut Method
Torque-Limited Fasteners
Load-Indicating Washers
Torsional Stress Due to Torquing of Bolts


15.10 Fasteners in Shear

Dowel Pins
Centroids of Fastener Groups
Determining Shear Loads on Fasteners


15.11 Case Study 8D
15.12 Summary
15.13 References
15.14 Bibliography
15.15 Problems


Weldments

16.0 Introduction
16.1 Welding Processes

Types of Welding in Common Use
Why Should a Designer Be Concerned with the Welding Process?


16.2 Weld Joints and Weld Types

Joint Preparation
Weld Specification


16.3 Principles of Weldment Design
16.4 Static Loading of Welds
16.5 Static Strength of Welds

Residual Stresses in Welds
Direction of Loading
Allowable Shear Stress for Statically Loaded Fillet and PJP Welds


16.6 Dynamic Loading of Welds

Effect of Mean Stress on Weldment Fatigue Strength
Are Correction Factors Needed For Weldment Fatigue Strength?
Effect of Weldment Configuration on Fatigue Strength
Is There an Endurance Limit for Weldments?
Fatigue Failure in Compression Loading?


16.7 Treating a Weld as a Line
16.8 Eccentrically Loaded Weld Patterns
16.9 Design Considerations for Weldments in Machines
16.10 Summary
16.11 References
16.12 Problems


Clutches and Brakes

17.0 Introduction
17.1 Types of Brakes and Clutches
17.2 Clutch/Brake Selection and Specification
17.3 Clutch and Brake Material
17.4 Disk Clutches

Uniform Pressure
Uniform Wear


17.5 Disk Brakes
17.6 Drum Brakes

Short-Shoe External Drum Brakes
Long-Shoe External Drum Brakes
Long-Shoe Internal Drum Brakes


17.7 Summary
17.8 References
17.9 Bibliography
17.10 Problems



Appendices

Material Properties
Beam Tables
Stress-Concentration Factors
Answers to Selected Problems