STRESS AND STRAIN

STRESS

•  The force across a small boundary per unit area.

• Derived from physical fundamental quantity like velocity,energy torque.

• Stress is a macroscopic concept.

• Its matter must be described by the tensor.

• The dimension is that of pressure.

• Stress is a material body due to multiple physical causes like internal influence etc.

• In some solid material such stress will generate a internal elastic stress.

• Stress that exceeds certain strength of the material will result in permanent deformation.

• It is the internal resistance set up by body when it deformed.

• It is measure in n/m2

TYPES

1. Tensile
2. compressive
3. shearing

TENSILE STRESS

COMPRESSIVE  STRESS

• If the bar is subjected to axial compresion rather then axial tension then the stress developed called stress compression

SHEAR STRESS

• It is also called tangential stress and denoted by q
• Q=r/a

     

STRAIN

• Strain is the measure of deformation representing the displacement particles of the body.
• It is generally a tensor quantity.
• It has a dimensionless quantity.
• It expressed in the form of decimal fraction or a percentage etc.
• Shrain can be decompose into normal and shear component

TYPES OF STRAIN

1. Longitudinal strain
2. Volumatric strain
3. Shearing strain

LONGITUDINAL STRAIN

It is defined as the change in length of the body to the original length of the body.

VOLUME STRAIN

• It is defined as the change in volume to the original volume.

SHEAR STRAIN

• It is the ratio of the displacement of the layer to its distance from fixed layer.

STRESS AND STRAIN EQUATION

• Hooke's law gives a relationship between strain and stress.According to hook's law,with in the elastic limit,strain produced in a body is directly proportional to the stress produced.