Tensile Stress

Stress is the restorative force exerted per unit area of a body. As a result, stress is defined as the magnitude of forces that cause deformation across a certain area.

Tensile stress occurs when forces draw on an object and induce elongation, as when an elastic band is stretched. Compressive stress occurs when forces cause an object to compress. Bulk stress occurs when a body is pressured from all sides equally, such as a submarine submerged underwater. The effective forces may not be tensile or compressive in some circumstances, but the deformation is still visible. When deforming forces operate tangentially to an object’s surface, the force is known as shear force, and the stress it produces is known as shear stress. 

Types of stress

In physics, there are various types of stress, however they are primarily divided into three types: normal stress, tangential or shearing stress and Bulk stress or volumetric stress. The next sections go over some of the different types of stress.

Normal stress

The restoring force acting perpendicular to the body’s surface is described as normal stress. Tensile and compressive stress are the two types of stress.

Tensile stress: 

Tensile stress occurs when two equal and opposite forces are applied to a circular rod to increase its length, with a restoring force equal to the applied force F normal to the rod’s cross-sectional area. Tensile stress is defined as the restoring or deforming force per unit area operating perpendicular to the body’s cross-section.

Formula for calculating tensile stress is:

σ=F/A

Here, is the tensile stress, F is the force acting on the body and A is the area of cross section upon which the force is acting.

Compressive stress:

Compressive stress occurs when two equal and opposite forces are applied at the ends of a rod to shorten its length. The restoring force or deforming force operating per unit area perpendicular to the body is characterised as compressive stress. In compressive stress the net force acting on an object under tensile or compressive stress is zero, but the object is distorted. Tensile stress is also known as compressive stress or longitudinal stress.

Tangential stress

When two equal and opposite forces operate along the tangents to the surfaces of two opposing faces of an object, one face is displaced with respect to the other. In this situation, the item is subjected to tangential stress, also known as shearing stress. Tangential stress, often known as shearing stress, is defined as the ratio of the tangential force to the surface area.

Bulk stress

When an object is submerged in a fluid (liquid or gas), the fluid exerts a force on the object’s surfaces, as depicted in the diagram. As a result, the object’s volume shrinks, and the object is subjected to a tension known as bulk stress or hydraulic stress.

Properties observed when tensile force is applied on a body

The various tensile properties can be computed when a tensile force is applied to the material:

1. Elastic modulus: Elastic modulus, also known as modulus of elasticity, is the stiffness of a substance. When the deformation is completely elastic, it is defined as the ratio of stress and strain. The stress-strain curve is used to calculate elastic modulus.

2. UTS (ultimate tensile stress): When a force is exerted, it is defined as the maximum stress that a material can withstand. When materials are pushed beyond their Ultimate Tensile stress, cracking occurs.

3. Modulus of Resilience: The ratio of tensile stress to two times the material’s Youngs modulus is known as the modulus of resilience.

4. Fracture stress: Fracture stress is defined as the greatest stress that a crack can withstand before it breaks down, and it is symbolised by the letter f.

Tensile strain

The deformation or elongation of a solid substance caused by the application of a tensile force or stress is known as tensile strain. In other terms, tensile strain occurs when a body lengthens due to applied pressures attempting to “stretch” it. The following formula can be used to calculate tensile strain:

ε=ΔL/L

Here, ε denotes the tensile strain,  L is the change in length and L is the initial length.

Conclusion

Stress is defined as restoring force per unit area as a result when a deforming force is applied on the body, whereas strain is defined as elongation or contraction per unit length. To characterise the elastic behaviour of objects as they respond to deforming forces operating on them, we define three elastic moduli: Young’s modulus, shear modulus, and bulk modulus. The modulus of elasticity of a material is the ratio of stress to strain. 

Tensile stress is defined as the restoring or deforming force per unit area operating perpendicular to the body’s cross-section.