[Physics Class Notes] on Tensile Stress Pdf for Exam

When two people pull a rope from both sides oppositely, the rope stretches as far as it can, and at a point, it starts tearing up. When you pull the rope, the force is acting along the axis. This externally induced force that is acting per unit area of the material and stretching is called tensile stress and a material’s capacity to bear that stress till it is broken is called the tensile strength of the material. When there is an increase in the length of the material in the direction of the force applied, this kind of stress setup is called Tensile stress. 

 

Let’s discuss the types of stress: 

When a contorting force acts normally or perpendicularly over an area of a body, then the force established over a unit area of that body is called the Normal stress.

Tensile stress is one of the categories of normal stress.

Tensile stress is caused by an applied force or load that leans to elongate the material in the direction or axis of the force applied.

Let’s say molecule 1 and molecule 2 are fixed at their lattice points ‘p’ and ‘q’ respectively, packed together closely such that they remain in an equilibrium stage.

Now as the force ‘F’  is applied and the object loses its Elastic limit and elongates in the axis of the force ‘F’ applied because the molecules which were fixed with a distance ‘k = 0’ (with no void in between them) are set apart by some distance ‘k = d’. The elongation or we can say a permanent deformation by the tensile strain occurs in this way.

 

 

This is an image showing the elongation from Lo to Length L, but there will be a decrease in the diameter of the rod, hence the decrease in the area as well.

 

This decrease in the cross-sectional area due to tensile deformation provides the basis for the new name Neck.

 

Tensile Stress Formula

If the force is acting perpendicular to the surface is given by F, and the surface area is H, then tensile stress (T) is given by:

 

T = [frac {F} {H}]

 

S.I. unit of T = Pascal (Pa) or Newton per meter square or N x m^{– 2}

 

Dimensional formula for tensile stress =

M⁻¹L⁻¹T⁻² 

 

Tensile Strength

Any object has always got the endurance to withstand the stress or an external force acting upon it, but as we continue to apply the force the object reaches the breaking or a fracture point.

 

 

Tensile strength is the maximum stress without fracture a material can withstand before breaking. For example, when two persons pull a piece of cloth from both sides, to an extent the cloth stretches and starts tearing up after a certain extent. So, the point at which the cloth can stretch and start tearing up later is called the tensile strength of the cloth. Solids are more tensile and withstand more tensile strength than gases as the gases are free particles and solids are more compacted, the solids have more capacity to stretch. 

 

It measures the force required to stretch or pull something such as rope, wire, or any structural rod or a beam to the point where it fractures or breaks. 

 

For an axial load material, the breaking strength (Ts) is given by:

 

U = Force that causes the fracture or a breaking

 

V = Cross-sectional area of the material

 

Ts =  [frac {U} {V}]

 

S.I. unit = Pascal or Newton per meter square or N x m^{– 2}

 

Difference Between the Tensile Stress and Tensile Strength

Tensile Stress: It is defined as the stress which occurs along the sides of the object in the direction of force which would increase the length of the material in the tensile direction but the volume will remain constant. It acts along the axis and puts some stress on the material. The result of this force is stretching up of the material. 

Tensile Strength: It is the resistance of a material to breaking under tension. So if any object or a body has high tensile strength, which means that body can resist a lot of tension before it breaks. 

 

It indirectly tells us the ability of a material to withstand tensile stress. The result of the tensile strength is, when the force exceeds the tensile strength, it starts breaking up or tearing down. 

Tensile stress Vs Tensile Strain Vs Tensile Strength:

Tensile stress acts along the axis of the object and stretches the object. When the object stretches, the damage done by the tensile stress to it is known as the tensile strain and the extent to which the object can withstand before breaking up completely is known as its tensile strength of it. If the tensile stress is applied parallel to the object rather than perpendicular to it, the stress is known as the shear force or shear stress. And the compressive force is opposite to the tensile stress and we can see this force being used in the construction field, to build concrete pillars. To calculate the tensile stress applied on an object, divide the area on which the force is applied with the force applied.

Applications of Tensile Stress in Daily Life:

• Tensile stress is used by the police and movers to tow the cars and other vehicles.

• When you see anyone pulling up water from the well and carrying it, it is the tensile stress that works on the rope and pulley which makes bringing up the water possible.

• When the shopkeepers and vendors on the street use a weighing scale to measure the products, fruits, vegetables, etc, it is the tensile force that helps in doing it. 

• Many gym equipments like the Lat Pull machine, waistband works on the same principle and helps us work out every day

• A crane works on the same principle of tensile stress to pull up materials and place them elsewhere. 

• We see children playing whirligig and it is based on the principle of tensile stress

• Tug of war is another activity that is done based on the same principle.

• When you try to pull a heavy object like a big rock or a block with the help of a rope, you are using the tensile stress to drag it. 
  

Summary

When there is no permanent change in the configuration of the body, the restoring force is equal to the external force applied which means that:

 

Stress = [frac{text{external deformation force}}{text{area}}]

 

The solids are more elastic and gases are less elastic because for the given stress applied the gases are more compressible than that of solids.

 

Necking, in engineering or material sciences, is a modality of tensile deformation where comparatively huge quantities of strain focalize disproportionality in a tiny region of the material. The ensuing salient decrease in the local cross-sectional area furnishes the basis for the name “neck”.

 

Multiwalled Carbon nanotubes have the highest tensile strength among all the materials.

 

A quantity (Y) Young’s modulus relates how difficult it is to stretch a given material, and is described by:

 

Tensile Stress  =  Y  x Tensile Strain

 

Therefore, [frac{text{Tensile Stress}}{text{Tensile Strain}}] = Y = a constant