Elasticity
- 1. ELASTICITY
- 3. PLASTICITY
- 4. Comparison b/w elasticity & plasticity
- 5. Examples of elastic materials • 1 Natural gum • 2 Spandex or lycra • 3 Butyl Rubber (GDP) • 4 Fluoroelastomer • 5 Elastomers • 6 Ethylene-propylene rubber (EPR) • 7 Resilin • 8 Styrene-butadiene rubber (SBR) • 9 Chloroprene • 10 Elastin
- 9. EXAMPLES
- 10. Stress
- 11. Types of stress • Types of Stress 1 Tensile stress 2 Compressive stress 3 Shear stress 4 Torsional Stress
- 12. Tensile stress • When a material is subjected to two equal and opposite axial pulls, the material tends to increase in length. • The resistance offered against this increase in length is called tensile stress. • E.g.: 1 When brake is applied the brake rod is under tensile stress. • 2 During tightening of bolt or nut. • 3 Belt driving the fan. • 4 Crane rope (When rope is pulling)
- 14. Compressive stress • When a material is subjected to two equal and opposite axial pushes, the material tends to decrease in length. • The resistance offered against the decrease in length is called compressive stress. examples • 1 Compressive stress on connecting rod on the first part of power stroke • 2 Compressive stress on push rod during valve opening
- 16. Shearing stress • When a material is subjected to two equal and opposite forces acting tangentially across the resisting section, the body tends to be sheared off across the cross section. The stress included is called shear stress. • It is represented by τ • Eg. • 1 Rivets • 2.Gear box shaft • 3Axle shaft
- 18. Torsional stress • When a shaft is subjected to the action of two equal and opposite couples acting in parallel planes, then the shaft is said to in torsion. The stress set up by the torsion is known as torsional shear stress. • Eg. • 1.Crank shaft • 2.Starter motor armature shaft
- 19. STRAIN • When an external forces acting on a material, there is a change in its dimension and shape. The deformation is called strain • strain is the ratio between the change in dimension of a material to its original dimension • It has no unit. • It is represented by ε (Epsilon)
- 21. TYPES OF STRAIN • Linear or Longitudinal strain Tensile strain Compressive strain Shearing strain • Lateral Strain • Volumetric Strain
- 22. Linear strain It is the ratio between the change in length of the material to its original length.
- 23. Tensile strain
- 25. Shearing strain
- 26. Lateral strain
- 28. Poisson’s ratio