 # Compressive Stress

Compressive stress is the restoring strain developed because of pressure or force applied on a material to deform it, thereby causing reduction of its volume. This capability of materials to withstand such compression is known as compressive strength. Here, we will discuss these two essential terminologies in detail.

What Is Compressive Stress?

It is the measure of the restoring stress developed in a body as a result of force applied on a material for the intention of deforming it. The maximum force at which materials deform and its volume is reduced, is known as compressive stress. The value of stress may differ from one element to another. Let us understand this by taking two scenarios –

1. In case this force is applied on brittle materials, the material breakdowns into smaller particles because of the sudden release of energy.

2. In case the material is ductile, they can be compressed easily.

What is Compressive Strength?

It is the measure of the capacity of a material to withstand the external force applied on it with an intention to deform it. Once the compressive strength limit of a substance is attained, they may fracture or deform.

Therefore, as per compressive strength meaning, brittle materials are more likely to have higher compressive strength than ductile ones.

Kinds of Stress

One can deform a solid by applying external force. However, it is possible by only three ways as mentioned below.

1. Tensile Stress – It is the equal forces applied on a body perpendicular to its cross-sectional area to deform it.

2. Compressive Stress Definition – The solid is compressed by applying an external force. In response, the restoring force is produced in the body, which is known for compressive stress.

3. Shearing Stress – A tangential force developed in the solid body because of the application of two equal & opposite external forces parallel to its cross-sectional area is known as the shearing stress.

Formula

The compressive stress formula can be written as

σ = F/A

Where,

• σ is compressive stress.

• A is the unit area of a solid body.

• F is a compressive force.

This can also be used as the compressive strength formula as it is the limit at which the solid material deforms.

Units and Dimensions

SI unit for compressive stress or compressive strength unit can be expressed as Nm-2 or Pascal (Pa).

The dimensional formula for the same will be [M L-1 T-2].

## Tensile Stress vs Compressive Stress

 SI. No. Tensile Stress Compressive Stress 1 As a result of tensile stress, the solid material is elongated. Here, the solid material is compressed, or its volume reduces. 2 It is developed because of the application of the external stretching force. It is developed because of the application of the external compressive force. 3 Examples – Ropes, nails, thread, cables of crane, etc. Examples – Concrete pillars.

1. A material pulled with tension force experiences a reduction in the compressive strength.

1. True

2. False

Ans: a

1. Choose the material which has higher compressive strength than tensile strength.

1. Fibreglass

2. Silica

3. Cast iron

4. Alumina

Ans: a

1. Calculate compressive of a cylindrical body with a 2cm diameter and applied force of 10 N.

1. 450 kN/m2

2. 678kN/m2

3. 875 kN/m2

4. 796 kN/m2

Ans: d

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