Stress and its types

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stress

STRESS

Stress Diagram
Stress Diagram

When some external system of forces or loads act on a body, the internal forces (equal andĀ opposite) are set up at various sections of the body, which resist the external forces. This internalĀ force per unit area at any section of the body is known as unit stress or simply a stress. It is denotedĀ by a Greek letter sigma (Ļƒ). Mathematically,

Stress, Ļƒ = P/A
where,

Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā P = Force or load acting on a body, and
A = Cross-sectional area of the body.

In S.I. units, the stress is usually expressed in Pascal (Pa) such that 1 Pa = 1 N/m2. In actualĀ practice, we use bigger units of stress i.e. megapascal (MPa) and gigapascal (GPa), such that

1 MPa = 1 Ɨ 106 N/m2 = 1 N/mm2

and Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā  Ā 1 GPa = 1 Ɨ 109 N/m2 = 1 kN/mm2

 

Reference

A textbook of Machine Design by R.S.Khurmi and J.K.Gupta

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