Pressure and Stress

Standard

The pressure and stress both have same unit N/m^2.then what is difference between them……….?

  • Pressure : Intensity of external forces acting on a body per unit area. For example :Atmospheric Pressure – Its the pressure exerted by air on surface of earth.

    Stress is Internal Resistance offered by a body to external forces per unit area. Taking an example of Rubber Material. You apply some force and it deforms. But assume it doesn’t deforms; then what happens, material is applying force equivalent to external force. That opposite force in termed as Internal Resistance and its ratio with area is called Stress.

  • Basically in simple words,
    1)pressure ‘acts’ on body whereas stresses are ‘induced’ or ‘developed’.
    2)pressure is something what we apply or gets applied on body due to external loading like torque, force; to this the internal reaction developed automatically is stress.
    3) various strain gauges are available to measure stresses.
    4) stress is not vector, its tensor; it has direction and orientation(plane in which it acts) as well.

 

  • 1. pressure represent intensity of external forces acting at a point. but stress represent intensity of internal resisting forces develop at a point.
    2. pressure is always acts normal to the surface. but but stress may also act either normal or parallel to the surface.
    3. magnitude of pressure at a point in all direction remain same. but magnitude of stress at a point in all the direction are unequal.
    4. pressure can be measure by using measuring device.like pressure gauge. but stress can’t be measure directly by using any device.
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