Stress - Definition, Unit, Types, FAQs

What is Stress?

Stress definition is, the force that acts on a body of per unit area. The effect of stress causes strain in the material. Stress is the process which helps to deform the material. Stress in physics, helps us to understand the force that a material or object experiences.

What is the unit of stress?

Stress meaning, the force that acts on a material in a unit area.

So, The SI unit of stress is $\mathrm{N} / \mathrm{m}^2$ (pascal، Pa ).

The CGS unit of stress is dyne/ $\mathrm{cm}^2$.

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This Story also Contains

1. What is Stress?
2. What is the unit of stress?
3. Types of Stress

Types of Stress

A. Tensile Stress or Normal Stress

The tensile stress definition is given below-

The external force per unit area of material resulting in a stretch of material is known as tensile stress. We say that the object is in tension. The subscript is a reminder that force acts perpendicular to the cross-section.

We define tensile stress at cross-section as ratio of force F to cross-sectional area A:

Normal stress=FA----(1)

This is a scalar quantity. The SI unit of stress is pascal. Equation (1) shows that 1 pascal equals 1 newton per square meter (N/m²) :

$1 \mathrm{~Pa}=1 \mathrm{~N} / \mathrm{m}^2$

The unit of stress is the same as that of pressure. Air pressure in automobile tires is typically around 300 kPa.

B. Shear stress or tangential stress

The figure shows a body being deformed by shear stress. A force acting in a generally horizontal direction especially or force that produces mountain folding and over thrusting.

C. Bulk stress or Volumetric stress

Thus, bulk stress or volume stress is also can be called as pressure.

Bulk stress or Volume stress=p=FA.

Hooke’s Law

Hooke’s Law is defined as the ratio of stress to strain.

StressStrain=Hooke's Law (Elastic Modulus)

The relation between stress and modulus of elasticity:

1. Young's Modulus Y=Tensile stress or Normal stressTensile strain or normal strain
2. Shear Modulus G=Shear stress or tangential stress shear strain or tangential strain
3. Bulk Modulus B=Normal stressVolume strain

Thermal stress

The stress which is developed due to the rise or fall in temperature is known as thermal stress.

Let us consider that a rod of length $L$ is fixed between two rigid walls and is heated to raise the temperature by $\Delta \theta$. Hence, due to the rise in temperature, there develops a strain which is represented by $\Delta L L$.

From Young's Modulus $Y=$ Stress/Strain
We get, Stress $=Y \times$ Strain $=Y \Delta L / L$.

Relation between Stress and Elastic Potential Energy

Elastic Potential energy is defined as total work that is done against the restoring force that stretches a material by any length.

The relation with stress is,

Elastic Potential Energy

$U=\frac{1}{2}$ Stress $\times$ Strain

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