Learn about the Stress Strain Curve

A Stress-Strain Curve is a graphical representation of a material’s Stress and Strain. The Y-axis represents stress, while the X-axis represents strain.  

This Stress and Strain curve depicts the relationship between stress and strain, as well as the material’s stress behaviour as strain increases. The stress-strain curve is widely used in material science and mechanical engineering to understand the strength, deformation, and failure criteria of any material. In this article, we will go over the stress-strain curve in greater detail.

 What is Stress Strain Curve?

 The two plotted characteristics are stress on the y-axis and strain on the x-axis. The ratio of the load or force to the cross-sectional area of the material to which the load is applied is defined as stress. Stress is commonly measured in pounds per square inch or Newtons per square metre squared.

 Strain, on the other hand, is a measure of the material’s deformation as a result of the applied force. A change in the shape or form of a material is referred to as deformation. 

A person standing on the end of a diving board, for example, causes it to deform or bend as a result of the weight or force. Strain has no unit of measurement because it is a ratio of deformation to initial length. If the strain measured is 0.05, for example, this means that there is 0.05 inch of deformation for every inch of length. 

Materials are classified into two types: brittle materials and ductile materials. Brittle materials, such as glass, will break or fracture without bending if a sufficient force is applied. When a force is applied to a ductile material, such as steel or aluminium, it will bend. If the force is sufficient, the material will permanently deform and will not return to its original shape.

 Ductile Stress Strain Curve 

A point labelled yield strength, also known as yield point, can be seen on this ductile material curve. The curve’s dip at this point indicates that the material has yielded or deformed. This deformation will be permanent once the load is removed. The material is elastic up to this point. When a load is applied to an elastic material, it deforms but returns to its original shape once the load is removed.

Stress Strain Curve for Mild Steel

When a ductile material, such as mild steel, is subjected to tensile force, it goes through several stages before failing. The graphical representation of this stage is the stress strain curve. Different materials may have varying curves. Ductile materials typically follow a similar pattern, as do brittle materials. The following is an explanation of the stress strain curve for mild steel, a ductile material. 

Here is a list of the various stages that a ductile material goes through when subjected to force until it fails.

 -Limitation in proportion (point A)

-Limitation of elasticity (point B)

-Point of yield (upper yield point C and lower yield point D)

-The ultimate source of tension (point E)

-The tipping point (point F) 

Proportional limit

 Stress and strain have a relationship up to point A, as shown in the stress strain curve for mild steel. This is referred to as Hooke’s law. Stress followed strain directly up to the limit of proportionality. This means that the stress-to-strain ratio remains constant.

 Ultimate stress

 This is the maximum amount of stress that a material can withstand. The ultimate stress is the value of stress that corresponds to the peak point on the stress strain curve for mild steel. In the diagram, it is denoted by point E

 Elastic limit

 The amount of stress up to which a material behaves like it is perfectly elastic is referred to as the elastic limit. Point B in the diagram represents the elastic limit point. If the load is removed, the material can revert to its original shape if it does not cross point B.

 Breaking stress

 The breaking point is the point on the stress strain curve where the material fails. Breaking stress is the stress that corresponds to this point.

 Yield limit

 This is the maximum amount of stress that a material can withstand. The ultimate stress is the value of stress that corresponds to the peak point on the stress strain curve for mild steel. It is denoted by the letter E.

 Fracture point

 The fracture point in the curve is denoted by the letter F. The fracture point is the point at which the material’s strength breaks, and the strength at this point is referred to as the rupture strength. 

Conclusion 

A Stress-Strain Curve is a graphical depiction of the Stress and Strain of a material. This Stress and Strain curve demonstrates the connection between stress and strain, as well as the stress behaviour of the material as strain grows. Stress is defined as the ratio of the load or force to the cross-sectional area of the material to which the load is applied. Strain, on the other hand, is a measurement of the deformation of a material as a result of applied force. The stress strain curve is a graphical depiction of this stage. The ultimate stress is the stress value that corresponds to the maximum point on the stress strain curve for mild steel.