All About What is Compressive Stress

Have you heard of a rubber ball? You might have tried to squeeze it at some point, right? What happened when you squeezed it? “The answer is quite simple”, you’ll say, “it will shrink in size!” 

Well, that is correct; the rubber ball, when squeezed, will hardly shrink for some time, after which it will take on its usual shape. But what happens is that the squeezing action causes stress in the rubber ball, an elastic object, which leads to a decrease in its volume.

In this example, the squeezing action is called compressive force, and the stress caused by this force is called compressive stress. 

Definition

Stress measures the quantity of external forces acting upon a body, causing it to deform. Compressive stress is a type of stress which is caused by applying a maximum pushing force to a body that leads to deformation. If maximum force is exerted on a body that leads to a decrease in its volume, it is called compressive stress. 

The maximum pushing force is called compressive force. The most famous example of compressive stress is football. When a player kicks the ball, the kicking action causes the ball to shrink in its size before going forward. 

Here, because the ball decreases in shape, we can safely say that compressive stress is acting on the ball. If the magnitude of stress is negative, it is generally considered compressive stress; however, if the magnitude is positive, it is considered a tensile force.

Formula

Compressive stress is dependent on two factors, the unit surface area of the body and the applied force. Mathematically it is defined as ‘the force applied on a unit surface area of the body.’ 

The mathematical formula to calculate compressive stress is given below,

CS = F/A

where-

CS is the compressive stress

F is the compressive force, or applied force

A is the unit surface area of the object.

The SI unit of compressive stress is called Pascal or Newton per metre squared(Nm-2)

Types of Stress

Apart from compressive stress, there are two types of stress. They are- 

Tensile Stress:

The force applied perpendicularly to a body to deform it is called tensile stress. The perfect example of tensile stress is the game of ‘Tug of War’. The rope used in the game is constantly under tensile stress caused by the pulling force at both ends. 

Shear Stress:

 The deformation of a body caused by the two forces acting opposite to it is called shearing stress. You will be surprised to know how much of an influence shearing stress has in our daily life. All our daily actions like chewing food, walking, travelling on a bus, and even applying lotion to our faces are examples of shear stress.

Comparison between Tensile and Compressive Stress

Application of Compression Stress

• Compression Testing

Compression testing is one of the major implementations of compression stress. It is a technique to see how a material reacts to compressive forces such as squashing, crushing, or hammering. Technically, it helps to find out the elastic limit of the material. The elastic limit is defined as the maximum force required to either break or permanently deform the material.

Compression testing is incorporated in industries to test if their products can withstand heavy compression. The mattresses and foams are tested to see how they react when maximum force is applied to them, thus further improving the quality of the product. Engineers must use compression-tested materials while building bridges, skyscrapers, and houses since these buildings constantly indulge themselves with compressive stress. 

• Blacksmith

Almost all products of iron and steel and other similar metals such as swords, knives, etc., are made by constantly hammering the iron to deform desired shapes perfectly. Compression stress is one of the key factors in determining the quality of any blacksmith products.

Conclusion

In this article, we learned that compression stress is a type of stress which is caused by compressive force. We also learned that a compressive force is a maximum force applied to the body that causes its size to shorten or shrink. Compression testing is an implementation of compressive stress, which industries use to improve the quality of their product. The main difference between tensile and compressive stress is that the tensile stress tends to elongate the body, whereas the latter tends to shorten the body’s shape.