Page 7 - Tribology in Machine Design

vi Contents

2.12 Relation between fracture mechanics and wear 45
2.12.1. Estimation of stress intensity under non-uniform
applied loads 47
2.13. Film lubrication 48
2.13.1 Coefficient of viscosity 48
2.13.2. Fluid film in simple shear 49
2.13.3. Viscous flow between very close parallel surfaces 50
2.13.4. Shear stress variations within the film 51
2.13.5. Lubrication theory by Osborne Reynolds 51
2.13.6. High-speed unloaded journal 53
2.13.7. Equilibrium conditions in a loaded bearing 53
2.13.8. Loaded high-speed journal 54
2.13.9. Equilibrium equations for loaded high-speed
journal 57
2.13.10. Reaction torque acting on the bearing 59
2.13.11. The virtual coefficient of friction 59
2.13.12. The Sommerfeld diagram 60
References 63
3. Elements of contact mechanics 64
3.1. Introduction 64
3.2. Concentrated and distributed forces on plane surfaces 65
3.3. Contact between two elastic bodies in the form of spheres 67
3.4. Contact between cylinders and between bodies of general
shape 70
3.5. Failures of contacting surfaces 71
3.6. Design values and procedures 73
3.7. Thermal effects in surface contacts 74
3.7.1 Analysis of line contacts 75
3.7.2. Refinement for unequal bulk temperatures 79
3.7.3. Refinement for thermal bulging in the conjunction
zone 80
3.7.4. The effect of surface layers and lubricant films 80
3.7.5. Critical temperature for lubricated contacts 82
3.7.6. The case of circular contact 83
3.7.7. Contacts for which size is determined by load 85
3.7.8. Maximum attainable flash temperature 86
3.8. Contact between rough surfaces 87
3.8.1. Characteristics of random rough surfaces 87
3.8.2. Contact of nominally flat rough surfaces 90
3.9. Representation of machine element contacts 94
References 96
4. Friction, lubrication and wear in lower kinematic pairs 97
4.1. Introduction 97
4.2. The concept of friction angle 98
4.2.1. Friction in slideways 98
4.2.2. Friction stability 100