Strength & Elasticity

Stress And Strain: 

Stress And Strain Presented By Bhutka Jignasha K 1 (10-001-2009)

Strength of Materials: 

Strength of Materials Engineering discipline concerned with the ability of a material to resist mechanical forces when in use. Strength of Materials, also referred to as Mechanics of Materials, looks at the behavior of materials when forces are applied to them. These forces include different types of stresses upon and within the material in all different directions, and the strain that is experienced in the material due to those forces.

Stress: 

Stress Every material in a elastic nature Whenever some external forces (loads) acts on a body, it under goes some deformation. As the body undergoes deformation, its molecules setup some resistance to deformation This resistance per unit area to deformation, is known as stress

Three basic type of Stress: 

Three basic type of Stress Tensile Stress When a section is subjected to two equal and opposite pulls and the body tends to increase its length, the stress induced is called tensile stress Stress that acts to lengthen an object. Compressive Stress When a section is subjected to two equal and opposite pushes and the body tends to shorten its length, the stress induced is called Compressive Stress Stress that acts to shorten an object. Shear Stress Stress parallel to the plane is usually denoted " shear stress " Generally defined as shear acts to change the angles in an object.

Strain: 

Strain Whenever a single force acts on a body, it undergoes a some deformation. Strain is defined a the ratio of change in dimension to original dimension of a body when it is deformed. It is a dimensionless quantity as it is a ratio between two quantities of same dimension.

Elasticity and Elastic limit: 

Elasticity and Elastic limit Elasticity of a body is the property of the body by virtue of which the body regains its original size and shape when the deformation force is removed. Most materials are elastic in nature to a lesser or greater extend, even though perfectly elastic materials are very rare. The maximum stress up to which a material can exhibit the property of elasticity is called the elastic limit. Beyond the elastic limit, the material gets into plastic stage and in this stage the deformation does not entirely disappear, on the removal of the force. There is some residual deformation is remains after removal of the force.

Hook’s Low: 

Hook’s Low When a material is loaded, within its elastic limit, the stress is proportional to the strain. Where, E= A constant of proportionality known as or Modulus of Elasticity or Young’s Modulus

Poisson’s Ratio: 

Poisson’s Ratio Any direct stress is accompanied by a strain in its own direction and called linear strain and an opposite kind strain in every direction at right angles to it, lateral strain. This lateral strain bears a constant ratio with the linear strain. This ratio is called the Poisson’s ratio. Value of the Poisson’s ratio for most materials lies between 0.25 and 0.33