What is Stress-Strain Curve: Graph and Types

When a component is manufactured, the workpiece is subjected to different forces, such as stress and strain. These two terms have their meanings in depth, which helps us determine their significance.

If you also want to understand everything about stress-strain curves, the guide below has it all. So, let's read.

What is Stress?

Stress is a type of force that is applied to the material. It also features the different types of reactions a material may possess when it is under force. There are two types of stress, as discussed below.

Tensile Stress

Tensile stress is applied to the materials when they are elongated and stretched in length. An example is stretching a rod to increase its length. During tensile stress, the material is pulled from both sides.

Compressive Stress

Compressive stress is applied to the materials when they are compressed, and due to being squeezed, their size is shrunk. The force is applied from both sides equally.

What is Strain?

Strain refers to the deformation that takes place in the workpiece when subjected to force. The change in the shape and dimensions of the materiali is caused due to the force applied in strain. There are two types of strains.

Tensile Strain

In tensile strain, the material is elongated due to the pressure applied, causing deformity.

Compressive Strain

Compressive strain is applied on the material, making it deformed in a compressive way, with a shrunk size.

What is a Stress-Strain Curve?

The stress-strain curve is a graph that shows the change in the stress when strain increases.

It is very widely used in manufacturing to understand the nature of materials. It helps determine the behavior of the material– which is ductile based on the stress.

Stress and strain curves are meant for materials that are brittle and hard but should be ductile. Below is a stress-strain curve.

Why is Stress-Strain Curve Important?

The stress-strain curve is important because it provides engineers with the essential parameters that are required for designing. This graph has various mechanical properties like yield point, toughness, elasticity, and elongation.

Explaining Stress-Strain Graph

The stress-strain graph has multiple elements, with each having its significance. Below, you will find a detailed insight into each of these elements.

Proportional Limit

The proportional limit is the end point of the linear part of the curve; it’s Young's modulus that can be pulled by calculating the slope.

Elastic Limit

It represents the point for elastic deformation.

Yield Point

The yield point is also an elastic limit, but it can be calculated.

Ultimate Stress Point

It is the maximum amount of stress on the curve, after which necking will start. It is very important to ensure that it is at the peak point of the curve, after which material can break.

Fracture or Breaking Point

The breaking point is that point on the curve on which the deformity of the material is observed, and it is either fractured or broken.

Hooke’s Law

Hooke’s law explains the concept of elasticity and how the force can either compress or extend the object. It considers elasticity by a given distance, which is proportional to the force. The higher the force, the more the distance. The formula for Hooke's Law is given below.

Hooke’s law states that in most metals, the more internal force there is, the more changes there are in length. It means that the stress and strain are directly proportional. Metalli have elasticity only to a certain extent.

How to Read the Graph?

The stress-strain curve can be read in the way suggested below.

• Select the value of stress on the y-axis.
• Create a horizontal line in front of the y-axis to intersect it with the line of the curve and mark that point.
• Draw a line vertically, then from the point of intersection to the x-axis; these lines will form a right angle.
• The value picked in the first step of stress shows that stress responds to the deformation of the material at the given point.

Types of Stress and Strain

The two types of stress and strain are explained below.

Engineering vs. True Stress and Strain

Engineering Stress and Strain

Engineering stress and strain help to get the values equal using the standard tensile test to get an idea of material behavior. This type is also called nominal stress and strain. The formula for engineering stress and strain is as follows:

True Stress and Strain

The actual stress and strain is the true stress and strain. It helps in understanding material properties, and to calculate it, you will need the applied load, gauge length, and the cross-sectional area. The following formulas can be used to calculate true stress and strain.

Stress vs. Strain Curves for Different Materials

The stress vs strain curve gives an insight into the way materials behave when force is applied to them. It highlights multiple properties of material fracture points, elasticity, and yield strength.

Metals like steel have a linear elastic region and are ductile. Polymers, on the other hand, have a nonlinear elasticity consisting of large deformation without any specific yield point.

When it comes to considering glass and ceramics, they are brittle and have steel curved with sudden fracture. Such curves are meant to help engineers select the material based on the stress they can handle.

Conclusione

The stress-strain curve plays a vital role when it comes to analyzing materials for manufacturing components. We at DEK analyze the stress-strain curve before we manufacture the components, so let us serve you with the right materials.