An introduction to Compressive Stress
When force is applied to an elastic band it stretches and when it does stretch it tends to undergo stress during the stretching. When the stress on the elastic band has reached its limit it tends to break and hence releasing the stress that was held by the elastic band. This stress is one of the factors that give it a shape. However, not every object is elastic in nature. Some are rigid and hence cannot be easily malleated even after providing an ample amount of stress to the material. One of the typical examples is a ping-pong ball which is quite brittle as it is made of plastic. Under stress, it tends to break and now holds a shape.
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Compressive stress is the restoring strain developed because of pressure or force applied on a material to deform it, thereby causing a 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 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 their 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 –
In case this force is applied to brittle materials, the material breakdowns into smaller particles because of the sudden release of energy.
In case the material is ductile, it can be compressed easily.
What is Compressive Strength?
It is the measure of the capacity of a material to withstand the external force applied to it with an intention to deform it. Once the compressive strength limit of a substance is attained, it 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.
Tensile Stress – It is the equal force applied on a body perpendicular to its cross-sectional area to deform it.
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.
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 units for compressive stress or compressive strength units 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
Questions to Answer
1.A material pulled with tension force experiences a reduction in the compressive strength.
True
False
Ans: a
2.Choose the material which has higher compressive strength than tensile strength.
Fibreglass
Silica
Cast iron
Alumina
Ans: a
3.Calculate compressive of a cylindrical body with a 2cm diameter and applied force of 10 N.
450 kN/m2
678kN/m2
875 kN/m2
796 kN/m2
Ans: d
While these concepts help you score high grades in academics, these can also have practical applications. Therefore, strengthen your knowledge of the basic concepts of Physics and ensure fulfilling your academic pursuits.
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Types of Test that is Used to Test Compressive Stress
The compressive stress test will allow the determination of the behaviour of a material when it is exposed to a huge amount of compressive stress. The three types of tests can be provided as follows:
Flexure test
Crushing test
Spring test
Conclusion
Compressive strength can be calculated using the ratio of the maximum force applied on a solid body to its cross-sectional area. It is the maximum compressive stress experienced by a body before deformation. Compressive Stress is extremely critical in the domain of designing structures and provides the retaining strength or capability of materials like concrete, etc.
FAQs on Compressive Stress
1.Why is it important to learn about Compressive Stress?
Vedantu provides a detailed outline on the topic of Compressive Stress - Definition, Formula, Units, Dimensions, and FAQ that will help students get to know about compressive stress and how it has been affecting various objects. Depending on this the objects can also be further classified as elastic, plastic, or non-malleable objects. This will also help in understanding the malleability of various metals and nonmetals. With the help of the Vedantu sample question paper for Physics, these concepts can be practised easily.
2.How is compressive stress different from tensile stress?
The following differences can be observed between compressive stress and tensile stress:
Compressive stress arises from squeezing the material while tensile stress is due to the stretching of the material
Compressive stress can be defined as the push provided to the body by external force application which results in a change of shape and size while tensile stress can be defined as the pulling of the body to change its shape and size.
Compressive stress is provided by using external forces while tensile stress is provided due to the elongation forces
When a bar will undergo compressive stress the strain will be negative while if the bar will undergo tensile stress then the strain will be positive.
3.What are the methods through which compressive stress can be induced?
There are three methods in which compressive stress can be induced and can be provided as follows:
1. Shot Peening:
This method is a cold working surface hardening method that leads to the increase in the surface area hardness by making use of fatigue resistance and deformation. In this method, small spheres of metal or ceramic undergo propelling through a pressurized flow.
2. Laser Shot peening:
Laser Shot peening allows the near-surface compressive residual stress and works hardening states. This also provides high resistance to crack initiation along with the propagation which improves the quality and life of the material.
3. Cavitation Peening:
In this process, there will be damage caused to the mechanical parts such as pumps or boat propellers. This process works by the production of cavitation bubbles that arise due to pressure changes.
4.How does learning about Compressive Stress help to apply the concepts in real life?
By learning about compressive stress students will be able to understand the following application in real life:
Conduction of actuation test and spring test in aerospace and automotive industry
The material involved in a concrete pillar is compressed by using compressive stress.
Various cosmetics products such as lipsticks, compact powders are fitted into the boxes with the help of compressive stress
For the packaging of cardboard and bottles along with PET bottles, compressive stress is used.
In order to make cricket balls and other balls tougher, compressive stress is applied. This allows the bouncy nature of the ball.
5.What is the compressive stress-strain curve and what does it tell about the compressive train involved?
Under the compression test, the stress-strain curve that is obtained will be a straight line until an elastic limit. Once this limit has been passed, there is a distinct bend that has been observed in the curve that represents the onset of the plasticity. The point at which this occurs will indicate the composite compressive yield stress which will be directly related to residual stress. The increase in residual stress will directly affect the compressive stress. In the compression test, the linear region is an elastic region that follows Hooke's law. Hence the region can also be represented as follows:
E = Young’s modulus
In this particular region, the material will behave elastically and will return to its original position once the stress has been removed.