UNIT - III.pptx...........................

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1. UNIT - III ELASTIC CONSTANTS AND STRAIN ENERGY

2. Elastic constants Elastic constants are parameters that describe the elastic properties of a material. They describe how a material deforms under the influence of an external force and how it returns to its original shape when the force is removed. The main elastic constants are : Young’s modulus (E) Shear modulus or modulus of rigidity (C, N or G) Bulk modulus (K) Poisson’s ratio (n or 1/m)

3. Lateral strain It is the ratio of the change in lateral dimension to the original dimension. Lateral strain is induced along the direction perpendicular to the direction of application of load.

4. Poisson’s ratio The ratio of the lateral strain to the corresponding longitudinal strain within elastic limit is called Poisson’s ratio. It is represented by n (nu) or 1/m. For most of the material, Poisson’s ratio lies between 0.25 to 0.33

5. Volumetric strain When a body is subjected to an axial pull or push, it undergoes change in its dimensions and hence its volume will also change. The ratio of change in volume to the original volume is known as volumetric strain.

6. Bulk modulus When a body is subjected to three mutually perpendicular stresses of same magnitude, the ratio of the direct stress to the corresponding volumetric strain is known as bulk modulus or bulk modulus of elasticity . It represents the resistance of a body against volumetric strain. It is usually denoted by 𝐾

7. Proof resilience The maximum strain energy which can be stored in a body without permanent deformation is called its proof resilience. If fmax be the maximum stress at the elastic limit, then Proof resilience = ƒ 2 az m 2E × Volume

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