Force and Pressure

Compressive Stress

Compressive stress refers to the force that leads to the deformation of the material such that there is a reduction in the material’s volume. Furthermore, it is the stress that a material experiences which leads to a smaller volume. Moreover, high compressive stress leads to the material’s failure because of tension.

Introduction to Compressive Stress

Compressive stress is the stress on materials that causes them to have a smaller volume. Furthermore, when the application of the compressive stress takes place to the materials that are brittle, these materials fracture due to the sudden release of the stored energy. Moreover, when the application of the compressive stress takes place to the materials that are ductile, they tend to compress and no failure occurs.

When stretching of a solid body takes place by applying with two equal forces normal to cross-sectional area, tensile stress is said to have taken place. When the compression of a solid body takes place, there would be the development of restoring force because of an externally applied force called compressive stress. Also, when the exposure of a solid body takes place to two equal and opposite forces parallel to the cross-sectional area, there would be the development of tangential force called the tangential or shearing stress.

compressive stress

                                                                                                                           Compressive Stress

What is Compressive Strength?

Compressive strength refers to the maximum compressive stress that material experiences before its breakdown takes place. Experts can obtain it by dividing the maximum load by the material’s cross-sectional area.

Compressive strength tends to be comparatively higher for both brittle and ductile. Furthermore, compressive strength tends to resist compression, whereas tensile strength tends to resist tension.

Measurement of compressive strength often takes place on a universal testing machine. Also, the specific test method and conditions of measurement affect the measurements of compressive strength. Usually, experts report compressive strengths in relation to a specific technical standard.

Methods of Inducing Compressive Stress

Below are the three most popular methods of inducing compressive stress

1)Shot Peening

Shot peening is a cold-working surface hardening method that leads to an increase in the surface hardness by making use of fatigue resistance and deformation through compressive stresses. Furthermore, it is one of the oldest and most popular methods for surface hardening.

In shot peening, propelling of thousands of small metal or ceramic spheres (called shots) takes place towards the substrate through a pressurized air flow. Furthermore, the shot, during the process, suffers plastic deformation. Also, the shots are used under short periods of time so as to avoid material damage.

2)Laser shock Peening

Laser shock peening (LSP) produces beneficial characteristics of near-surface compressive residual stresses and work-hardening states. Furthermore, this leads to high resistance to crack initiation along with propagation which improves the fatigue life of the material.

3)Cavitation Peening 

Cavitation Peening refers to a phenomenon that damages mechanical parts such as pumps and boat propellers. As such, some experts see it as negative. Furthermore, the use of cavitation jets takes place for cutting, cleaning, and rust removal of metal parts.

Recently, a new method of peening by cavitation has become popular and it has been under development since the 1990s. Cavitation peening works by producing cavitation bubbles due to pressure changes.

As an increase takes place in the velocity of a stream of water, the pressure would decrease in accordance with Bernoulli’s law. When the pressure reaches the water’s vapor pressure, a phase transformation of the water occurs from liquid to gas.

The formula of Compressive Stress

Pascal (Pa) or Nm-2 is the SI unit of compressive stress.

The compressive stress formula is as follows:

σ=FA

Where,

  • σ refers to the compressive stress
  • F represents the compressive force
  • A is the unit area

The dimensional formula of compressive stress is [ML-1T-2].

FAQs For Compressive Stress

Question 1: Differentiate between compressive stress and tensile stress?

Answer 1: When it comes to compressive stress vs tensile stress, there are two main differences. Firstly, tensile stress results in a solid’s elongation, while compressive stress results in a solid’s shortening. Secondly, the tensile force happens due to external stretching force application, while compressive stress happens due to external compressive force application.

Question 2: What is meant by compressive stress?

Answer 2: Compressive stress is the stress that acts on materials that causes them to have a smaller volume. Furthermore, compressive stress refers to the force that leads to a reduction in the material’s volume.

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