Machine Design
Machine Design
S G Kulkarni
Department of Mechanical Engineering
Government College of Engineering
Aurangabad
Contents
Preface xiii
1 FUNDAMENTAL CONCEPTS 1
1.1 Force, Torque 1
1.2 Work, Power and Energy 2
1.3 Machine and Machine Elements 3
Worked Examples 3
Objective Questions 4
Review Questions 5
Practice Problems 5
Answers 5
2 DESIGN PROCEDURE, SIMPLE STRESSES 6
2.1 Induced Stress 6
2.2 Strength 6
2.3 LoadCapacity 6
2.4 Design of Machine Member 6
2.5 Factor of Safety 7
2.6 Design Procedure 7
2.7 Simple Stress: Different Situations 7
2.8 Manufacturing Tolerances 11
Worked Examples 12
Objective Questions 25
Review Questions 27
Practice Problems 28
Answers 31
3 COMBINED STRESSES: THEORIES OF FAILURE 32
3.1 Definition 32
3.2 Combined Bending Moment and Axial Load 32
3.3 Design Equation 32
3.4 Combined Normal and Shear Stress 33
3.5 Theories of Failure 34
3.6 Forms of Design Equations to be Used in Practice 35
3.7 Mohrs Circle Diagram 35
3.8 Practical Design Aspects 35
Worked Examples 36viii Contents
Objective Questions 41
Review Questions 42
Practice Problems 43
Answers 45
4 VARIABLE LOADING 46
4.1 Types 46
4.2 Endurance Limit 46
4.3 Design Equation for Machine Element Subjected to Variable Loading 47
4.4 Stress Concentration 49
4.5 Notch Sensitivity 49
4.6 Miners Equation 50
4.7 Loading in the Finite Life Range 50
4.8 Another form of Goodman Diagram 50
4.9 Designing for Variable Loading with Combined Stresses 50
4.10 Practical Design Aspects 51
Worked Examples 52
Objective Questions 60
Review Questions 61
Practice Problems 62
Answers 65
5 COTTER AND KNUCKLE JOINT 66
5.1 Introduction 66
5.2 Cotter Joint 66
5.3 Design Procedure 66
5.4 Knuckle Joint or Pin Joint 66
Worked Examples 66
Objective Questions 73
Review Questions 74
Practice Problems 74
Answers 75
6 DESIGN OF LEVERS 76
6.1 Introduction 76
6.2 Design Materials and Procedures 76
Worked Examples 76
Objective Questions 82
Review Questions 82
Practice Problems 82
Answers 84
7 SHAFTS AND COUPLINGS 85
7.1 Introduction 85
7.2 Design Equation 85
7.3 Weakening Effect 86
7.4 Different Types of Couplings 86Contents ix
Worked Examples 86
Objective Questions 99
Review Questions 100
Practice Problems 101
Answers 104
8 SPRINGS 105
8.1 Definition 105
8.2 Functions of Springs 105
8.3 Classification of Springs 105
8.4 Material 105
8.5 Design Equations for Close Coiled Helical Spring 105
8.6 Active Number of Turns N 107
8.7 Design of Carriage Spring 107
8.8 Spring with Extra Full Length Leaves 108
8.9 Design of Spring Subjected to Variable Load 109
8.10 Springs with Non-Circular Cross Section 110
8.11 Surging of Helical Compression Spring 110
Worked Examples 110
Objective Questions 119
Review Questions 120
Practice Problems 121
Answers 124
9 BOLT LOADING 125
9.1 Introduction 125
9.2 Design of Bolts for Easy Situation 125
9.3 Preloading of Bolts 126
9.4 Advantages of Preloading 127
9.5 Use of Spring Washers and Gaskets 127
9.6 Eccentric Loading of Bolts 127
Worked Examples 129
Objective Questions 135
Review Questions 136
Practice Problems 137
Answers 140
10 POWER SCREW 141
10.1 Introduction 141
10.2 Thread Profiles 141
10.3 Efficiency and Power Loss Due to Friction 141
10.4 Column Effect 143
10.5 Design Procedure 143
10.6 Other Varieties of Screws 144
Worked Examples 145
Objective Questions 158
Review Questions 159x Contents
Practice Problems 160
Answers 161
11 BELT, ROPE AND CHAIN DRIVE 162
11.1 Introduction 162
11.2 Types 162
11.3 Length of the Belt 163
11.4 Ratio of Tensions and Power Transmission 163
11.5 Centrifugal Tension 165
11.6 Flat and V Belt Comparison 165
11.7 Strength of Belt 166
11.8 Creep 166
11.9 Design Procedure 167
11.10 Design of Chain Drive 167
Worked Examples 168
Objective Questions 177
Review Questions 178
Practice Problems 179
Answers 182
12 BRAKES 183
12.1 Types of Brakes 183
12.2 Material 183
12.3 Design of Brakes 183
12.4 Block Brakes or Short Shoe Brake 183
12.5 Band Brake 184
12.6 Long Shoe Brakes 185
12.7 Pivoted Type Shoe Brake 187
12.8 Heat Dissipation in Brakes 188
Worked Examples 188
Objective Questions 199
Review Questions 200
Practice Problems 201
Answers 206
13 CLUTCHES 207
13.1 Introduction 207
13.2 Principle of Friction Clutches 207
13.3 Practical Design Aspects 209
13.4 Theory of Centrifugal Clutch 209
Worked Examples 210
Objective Questions 215
Review Questions 217
Practice Problems 218
Answers 220
14 SPUR GEAR 221
14.1 Definitions 221
14.2 Design Equations 223Contents xi
14.3 Wear Strength 224
14.4 Dynamic Tooth Load 224
14.5 Practical Design Aspects 226
Worked Examples 226
Objective Questions 240
Review Questions 241
Practice Problems 242
Answers 246
15 HELICAL GEARS 247
15.1 Introduction 247
15.2 Force Analysis 247
15.3 Equivalent Spur Gear: Formative Number of Teeth 248
15.4 Design Equations 248
15.5 Practical Design Aspects 249
Worked Examples 249
Objective Questions 258
Review Questions 260
Practice Problems 260
Answers 262
16 BEVEL GEARS 263
16.1 Introduction 263
16.2 Equivalent Relationships 264
16.3 Lewis Equation for Bevel Gear 264
16.4 Force Analysis 265
16.5 Practical Design Aspects 266
Worked Examples 266
Objective Questions 274
Review Questions 275
Practice Problems 276
Answers 277
17 WORM GEAR 278
17.1 Introduction 278
17.2 Nomenclature 278
17.3 Design Equations 278
17.4 Practical Design Aspects 279
17.5 Force Analysis 279
Worked Examples 280
Objective Questions 285
Review Questions 286
Practice Problems 287
Answers 288
18 SLIDING CONTACT BEARINGS 289
18.1 Introduction 289
18.2 Viscosity 290xii Contents
18.3 Petroffs Equation 291
18.4 Bearing Characteristic Number 291
18.5 Nomenclature 292
18.6 Heat Generated and Dissipated 293
18.7 Parameters Affecting the Bearing Performance 293
18.8 Sommerfield and Other Dimensionless Numbers 293
Worked Examples 294
Objective Questions 303
Review Questions 304
Practice Problems 305
Answers 307
19 ROLLING CONTACT BEARINGS 308
19.1 Introduction 308
19.2 Construction and Types 308
19.3 Definitions 309
19.4 Selection of Rolling Contact Bearing 311
19.5 Selection for Variable Loading 311
19.6 Preloading or Duplexing 312
19.7 Comparison between the Sliding and Rolling Contact Bearings 312
Worked Examples 313
Objective Questions 317
Review Questions 317
Practice Problems 318
Answers 320
20 MISCELLANEOUS ELEMENTS 321
20.1 Welded Joints 321
20.2 Design of Welded Joint 321
20.3 Design of Flywheel 323
Worked Examples 325
Objective Questions 331
Review Questions 332
Practice Problems 332
Answers 337
21 STATISTICAL CONSIDERATIONS AND OPTIMUM DESIGN 338
21.1 Statistical Considerations 338
21.2 Optimum Design 339
21.3 Statistical Consideration in Deciding Factor of Safety 339
Worked Examples 341
Objective Questions 345
Review Questions 345
Practice Problems 345
Answers 347
Appendix 1 348
Appendix 2 377
Index 390
Index
Acme threads 141
Active number of turns in helical springs 107
Addendum 221
Adequate solution 339
AGMA Power rating equation for worm gears 279
Allowable stress 7
Angle of obliquity 222
Angular contact ball bearings 308
Axial load 32
Back cone of bevel gear 264
Band and blockbrakes 183
Band brake 183, 184
Basic static load rating 309
Bearing pressure 8
Belleville spring 105
Belt drives 162
Bending 8
factor 265
gears 263
stress in the rim of flywheel 324
Bilateral method of tolerances 10
Bolt design 95
Box coupling 86
Boyde 293
Buckingham 224
Buckingham equation 249
Bushed pin type of flexible coupling 86
Butt joint 321
Buttress threads 141
Cage or retaining ring 308
Capacity 6
Carriage spring 107
Centrifugal
clutch 209
force 1
tension 165
Centripetal force 1
Chain drive 167
Circular pitch 221
Close coiled helical spring 105
Clutch 207
Cold working 51
Combined
bending moment and axial load 32
normal and shear stress 33
Condition of correct gearing 222
Cone clutch 207
Conjugate profiles 222
Conrod 308
Cotter joint 66
Creep 166
Cross belt 163
Dedendum 222
Deep groove type ball bearings 308
Design
equation 32
procedure 7
Direct compressive stress 8
Direct shear stress 8
Direct tensile stress 7
Disc spring 105
Disengagement factor 209
Double row angular contact ball bearings 309
Double shear 8
Duplexing 312Index 391
Dynamic tooth load 224
Easy situation for bolt design 125
Eccentric loading of bolts 127
Endurance
curve 47
limit 46, 49
test setup 47
Energy 2
of distortion 35
Engagement
factor 209
speed 210
Epicyclic gear train 226
Equivalent spur gear 248
Euler’s equation 142
Factor of safety 7
Fatigue life 50
Fatigue strength 47
Fillet weld 321
Filling type 308
Flange coupling 86
Flat
belt 162
spring 105
Flexible couplings 86
Flywheel 323
Force, torque 1
Forms of design equations 35
Friction clutches 207
Fulcrum 76
Gaskets 127
Gaussian distribution 338
Gerber’s parabola 48
Gib and cotter 66
Goodman’s line 48
Guest theory 34
Heat dissipation in brakes 188
Heat treatment—effect on fatigue strength 51
Helical rollers 309
Helical torsion spring 105
Herringbone gear 249
Hertz’s contact stress equation 224, 310
Hooke’s joint 86
Hoop stress 324
Hydrodynamic bearings 289
Hydrostatic bearings 289
Hydrostatic lubrication 290
Hypo cycloid 222
Hypoid gears 266
Induced stress 6, 7
Initial tightening 126
Inner race 308
Interference 222
interference fit 10
Involute 222
ISO metric threads 125
ISO trapezoidal threads 141
J.B. Johnson’s equation 142
Knuckle
joint 66
threads 141
Lanza’s approximation 330
Lap 321
Lasche’s equation 293
Leaf or carriage spring 105
Leaf spring 107
Lewis equation 223
Limit equations 339
Long shoe brakes 183, 185
Machine 2
element 3
Marine coupling 86
Mass moment of inertia 1
Maximum total strain energy theory 34
McKee’s equation 292
Mechanical brakes 183
Miner’s cumulative damage fatigue approach 311
Miner’s equation 50
Minimum number of teeth 222
Module 221
Modulus of elasticity 34
Mohr’s circle diagram 35
Multiple plate type clutch 207
Multistart threads 144
Natural tolerances 339
Newton 290
Non-filling type ball bearings 308
Notch Sensitivity 49
Oldham’s coupling 86
Open belt drive 163392 Index
Ordinary cantilever beam 108
Outer race 308
Pair of spur gears 221
Permissible elastic deformation 9
Petroff’s equation 291
Pin joint 66
Pinion 222
Pitch circle diameter 221
Pitch point 221
Pivoted type shoe brakes 183, 187
Pneumatic 183
Poise 290
Poisson’s ratio 34
Power screw 141
Prestressing—effect on fatigue strength 51
Preferred numbers 10
Preloading
of bearings 312
of bolts 126
Pressure anglef 222
Primary Design Equation (P.D.E) 339
Principal planes 33
Profiles 222
Protected type of flange coupling 86
R.C. Johnson 339
Rack 222
Raimondi and Boyde 293
Rankine theory 34
Rating life of a group of apparently identical ball 311
Reynold’s equation 293
Ribbed 162
Rigid couplings 86
Rolling contact bearings 308
Rolling elements 308
Round 162
SCF (Stress Concentration Factor) 49
Section modulus 9
Selective assembly 10
Self-aligning ball bearings 308
Self-energizing brakes 184
Self-locking 184, 187
Shaft 85
Shear energy 35
Short shoe brake 183
Single plate type 207
Sleeve and double cotter type 66
Sliding contact bearings 289
Soderberg 48
Solid muff 86
Sommerfield number 293
Spigot and socket type 66
Spiral
angle 266
spring 105
Split muff coupling 86
Spring 105
Spring washers 127
Spur gears 226
Square threads 141
St. Venant theory 34
Static equivalent load 311
Strength 6
Strength of belt 166
concentration 49
concentration factor 49
Striebeck equation 310
Subsidiary Design Equation (S.D.E) 339
Tension spring 105
Theories of failure 34
Thick film type lubrication 289
Thin film type lubrication 289
Tightening torque 126
Tommy bar 76
Toothed belt 162
Tredgold’s approximation 264
Turn buckle 157
Twisting 9
Unilateral method of tolerancing 10
Unit 290
V belt 162
Variable load 109
Variable loading 47
Viscosity 290
Von Huber Mises Hencky Theory 35
Wahl’s correction factor 106
Wear strength 224, 265
Welded joints 321
Work, power 2
Worm gear 278
Y factor for gears 223
Zerol bevel gear 266
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