Shearing Stress

Stress is basically a quantity which means how much deforming force applies per unit area of an object. The different kinds of stress where force is applied to an object in a different way is shear and tensile stress. Tensile stress is when a deforming force is applied at right angles to a surface. On the other hand, shear stress is where a deforming force is applied parallel to surface. Similarly, shearing is the process of parallel layers sliding past each other. We can push a pile of papers, a pack of cards with rectangular cross-section for getting a parallelogram cross-section. So, in this kind of cases, the angle between the sides change but all that has actually take place in some parallel sliding. Through this article, we will take a look at what shearing stress means and how to calculate it plus examples you can find in real life.

Introduction to Shearing Stress

When an external force is acting on an object, it will go through deformation. If the forceâ€™s direction is parallel to the plane of the object, the deformation is going to be along that plane. Thus, you see that the stress which the object experiences are shear or tangential stress.

It takes place when the force vector components are parallel to the materialâ€™s cross-sectional area. In the case of normal or longitudinal stress, the force vectors are perpendicular to the cross-sectional area on which it acts.

All in all, shearing stress is a kind of stress which acts coplanar with a cross-section of material. It takes place because of shear forces. They are the pair of forces which act on opposite sides of a body with the same magnitude and opposite direction.

Moreover, shear stress is a vector quantity. In other words, the direction here involves along with the magnitude. We denote it with the # Greek alphabet-Â Ï„.Â  Further, the SI unit of shear stress isÂ N/m2Â orÂ Pa.

How to Calculate Shearing Stress?

We can calculate the average shear stress by taking the ratio of force per unit area:

Ï„=Â F/A

Over here, Ï„Â refers to the shear stress whereas F is the force applied. Finally, A refers to the area of cross-section which is parallel to the force vector.

Shearing Stress in Fluids

We can observe shear stress in fluids as well. When a fluid is flowing within the boundary of solids, we can observe shear stress along with the point of contact between fluid and boundary.

Fluid consist of diverse levels, each level travel at different speeds. The layers that are at the same height from the boundary will experience the same speed. This changeable speed between the layers is basically caused due to shear stress.

Next up, in fluids,Â stress and strainÂ are connected differently. In other words, we that over here, shearing stress is relative to strain rate with viscosity as proportionality constant.

The meaning of shear is â€˜to cut offâ€™. When the force applies over the surface area of a rigid body (a force acting in a direction parallel to the surface), then this force will try to cut off one part of the body from the other.

Due to this, the body is deformed and thus it produces strain (shear strain- the angular deflection of the body from its original position). Moreover, because of the bodyâ€™s rigidity, it will defy the deformation which happens and a restoring force develops along the bodyâ€™s surface according to Newtonâ€™s 3rd law of motion.

This restoring force of the body will most likely oppose the shearing effect of the applied force. Therefore, shear stress is basically just an effect of shear strain.

Shearing Stress in Real Life

You will be amused to know that from the very moment that you wake up and get out of your bed to the one where you go back in it to sleep, you are surrounded by shearing stress. It is because almost every occurrence in our daily activities involves this stress. So, we will take a look at some examples of it in real life for a better understanding.

One example is all types of cutting (when you cut fruits, vegetables, tree, paper, cloth and more). Then, painting, brushing and applying creams or other stuff like soap, lotion, ointment and more.

When you chew feed between your teeth, it is also an example. After that, when you walk or run and your feet push ground back to move forward. Similarly, when a moving vehicle will start or stop, the seatâ€™s surface experiences shear stress.

Next, when water is flowing on river beds, they experience shear stress. Often, we can notice erosion as well due to this. One very common example in todayâ€™s date is when you are sliding on your Smartphone screens.

Another instance is also when we prepare Indian bread like Dosa, Pizza base, Roti and more. Next is when you polish the surface and write on the blackboard with chalk piece plus on sliding and more.

All in all, you see that all these instances, little and big, involve shearing stress. So, to list out all the examples is impossible as it is an unavoidable event in our daily life.

FAQ on Shearing Stress

Question 1: What is shear stress?

Answer 1: Shearing stress is a kind of stress which acts coplanar with cross-section of material. It takes place because of shear forces. They are the pair of forces which act on opposite sides of a body with the same magnitude and opposite direction.

Question 2: Give some examples of shearing stress.

Answer 2: When you chew feed between your teeth, it is an example of shear stress. After that, when you walk or run and your feet push ground back to move forward. Similarly, when a moving vehicle will start or stop, the seatâ€™s surface experiences shear stress.

Question 3: What is the difference between shear and tensile stress?

Answer 3: The different kinds of stress where force is applied to an object in a different way is shear and tensile stress. Tensile stress is when a deforming force is applied at right angles to a surface. On the other hand, shear stress is where a deforming force is applied parallel to surface.

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