What is Stress-Strain Curve?

Relationships between stress and strain can be plotted on a graph for most of the materials. In this experiment, the force is gradually increased, and it produces the strain. The values of the stress and the strain are plotted on a graph. This graph is called the stress-strain curve. These curves vary from material to material and are very helpful in giving a fair idea of how the material performs in different load conditions. 

In the graph, it can be seen that from O to A the graph is almost a straight line. It is the only region in this curve where Hooke’s Law is obeyed. 

Proportionality Limit

As after the point A or OA region, the graph doesn’t obey the Proportionality law or Hooke’s law, thus Point A is called the proportionality limit. 

Elastic Region

The initial region of the graph which is represented by graph OA is the Elastic Region. In this region, the material undergoes deformation under the applied street but returns to its initial state as stress is removed. In this region, Hooke’s Law is obeyed.

Elastic modulus

The slope of the Stress-Strain Curve in the elastic region is called the Elastic Modulus and this modulus represents the stiffness of the material. It is also called Young’s Modulus.

Yield point

The point in the Stress-Strain curve, from where the material started to deform plastically and can’t fully regain its initial state after stress is removed. In other words, the yield point is defined as the stress at which material starts to exhibit plastic deformation by some certain amount.

Yield strength

The required amount of stress to deform the given material 0.2-0.5% plastically, is called the yield strength of the material.

Ultimate Tensile Strength (UTS)

Ultimate Tensile Strength is the maximum amount of stress a material can handle before it breaks or fractures. It is a measure of the toughness of the material and generally measure in Pounds Per Square Inches (PSI).

Plastic Region

Plastic Region is part of the Stress-Strain curve, where the material undergoes plastic deformation permanently and can’t able to attain its initial state after the stress is removed.

Strain hardening modulus

The slope of the Stress-Strain Curve in the plastic region is called Strain hardening modulus and this modulus represents the ability of the material to resist further deformation.

Fracture point

The point in the Stress-Strain Curve, where material breaks in the experiment, is called the Fracture Point, and the stress or the force at this point is called Fracture strength.

Stress-Strain Curve is a very crucial concept in the study of material science and engineering. It describes the relationship between stress and the strain applied on an object. We know that stress is the applied force on the material, and strain, is the resulting change (deformation or elongation) in the shape of the object. For example, when force (stress) is applied to the spring, its length changes under that stress. But as stress is removed, spring came to its initial position.

Stress-Strain curve provides insights into the different materials under different levels of stress. This can help engineers design more efficient and strong structures. In this article, we will learn about, stress, strain, and the relationship between them and others in detail.