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Load. Stress. Strain. Tensile Stress and Strain. Compressive Stress and Strain. Young's Modulus or Modulus of Elasticity. Shear Stress and Strain Shear Modulus or Modulus of Rigidity. Bearing Stress. Stress-Strain Diagram. Working Stress. Factor of Safety. Selection of Factor of Safety. Stresses in Composite Bars. Stresses due to Change in Temperature—Thermal Stresses. Linear and Lateral Strain. Poisson's Ratio. Volumetric Strain. Bulk Modulus. Relation between Bulk Modul u s a n d Yo u n g ' s Modulus. Relation between Young's Modulus and Modulus of Rigidity. Impact Stress. Resilience. 4 Introduction 4.1 Introduction In engineering practice, the machine parts are subjected to. | CONTENTS C H A P T E R 4 Simple Stresses in Machine Parts 1. Introduction. 2. Load. 3. Stress. 4. Strain. 5. Tensile Stress and Strain. 6. Compressive Stress and Strain. 7. Young s Modulus or Modulus of Elasticity. 8. Shear Stress and Strain 9. Shear Modulus or Modulus of Rigidity. 10. Bearing Stress. 11. Stress-Strain Diagram. 12. Working Stress. 13. Factor of Safety. 14. Selection of Factor of Safety. 15. Stresses in Composite Bars. 16. Stresses due to Change in Temperature Thermal Stresses. 17. Linear and Lateral Strain. 18. Poisson s Ratio. 19. Volumetric Strain. 20. Bulk Modulus. 21. Relation between Bulk Modulus and Young s Modulus. 22. Relation between Young s Modulus and Modulus of Rigidity. 23. Impact Stress. 24. Resilience. 4.1 Introduction In engineering practice the machine parts are subjected to various forces which may be due to either one or more of the following 1. Energy transmitted 2. Weight of machine 3. Frictional resistances 4. Inertia of reciprocating parts 5. Change of temperature and 6. Lack of balance of moving parts. The different forces acting on a machine part produces various types of stresses which will be discussed in this chapter. 4.2 Load It is defined as any external force acting upon a machine part. The following four types of the load are important from the subject point of view 87 CONTENTS 88 A Textbook of Machine Design 1. Dead or steady load. A load is said to be a dead or steady load when it does not change in magnitude or direction. 2. Live or variable load. A load is said to be a live or variable load when it changes continually. 3. Suddenly applied or shock loads. A load is said to be a suddenly applied or shock load when it is suddenly applied or removed. 4. Impact load. A load is said to be an impact load when it is applied with some initial velocity. Note A machine part resists a dead load more easily than a live load and a live load more easily than a shock load. 4.3 Stress When some external system of forces or loads