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Stress – Definition, Types, Formula, Examples

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  • Last Updated : 01 Feb, 2022

The force exerted on the unit area of a substance is known as stress in physics. Strain is the name for the effect of stress on the body. Body deformities can be caused by stress. Stress units can be used to quantify how much force a substance has experienced. Depending on the direction of the deforming forces operating on the body, stress can be classified into three kinds. Furthermore, we are aware of human tension, but stress in physics is a little more difficult to comprehend. Let’s take a closer look at each of them individually.

Stress

There are a few principles that must be examined before discussing stress. Furthermore, stress is defined as the quantity of force we apply to an object divided by the cross-section area of the object on which the force acts. 

The item deforms when the deforming force is applied. There will be an opposing force generated inside the object in order to restore the object to its previous shape and size. This restoring force will have the same magnitude as the applied deforming force and will be in the opposite direction. The term “stress” refers to the measurement of this restorative force per unit area of the material.

Stress is defined as “The restoring force per unit area of the material”.

Stress is a Scaler quantity, and it’s denoted by σ. 

Stress is measured in Pascal or N/m2.

Formula of Stress 

Stress = Restoring force / Area of the material

σ = F / A

Where, Restoring force is measured in Newton, Area of the material is measured in m2, and Stress is measured in Pascal or N/m2.

Units of Stress

SystemStress unit
SI systemN/m2 or N/mm2
Fundamental systemkg.m-1.s-2
US unit (ft)lbf/ft2

SI System,

  1. Kilo (103): KN/m2 or KN/mm2
  2. Mega (106): MN/m2 or MN/mm2
  3. Giga (109): GN/m2 or GN/mm2
  4. Tera (1012): TN/m2 or TN/mm2

Types of Stress 

In physics, there are many different types of stress, but the most common are Normal Stress and Tangential or Shearing Stress. In the following paragraphs, we’ll go through a few different sorts of stress.

Normal Stress

The normal force is the stress that arises when an axial force is applied to a component. In other words, when the stress imparted to the body is perpendicular. When the object’s length and volume are altered, the object’s stress level returns to normal. The symbol is represented by it. Normal stress is measured in millipascals (MPa) in the SI system.

Formula of Normal Stress

Normal Stress = Axial Force / Cross-sectional Area

When an object is in tension or compression, normal stress occurs.

Longitudinal Stress 

Longitudinal stress is defined as when the length of the body changes due to normal stress.

Formula of Longitudinal Stress

Longitudinal Stress = Deforming force / Cross-sectional Area

Longitudinal Stress stretches or compresses an object throughout its whole length. As a result, based on the direction of deforming force, it can be divided into two types – Tensile stress and Compressive stress

When a rod is stretched according to Newton’s third law of motion, tensile stress is visible. Tensile stress is commonly represented by a rubber band being stretched out. Compression is the polar opposite of tension. When it is acting on a rod that is pressed at both ends by opposing or equal forces. Compressive stress is what you get when you squeeze a rubber ball in your hands.

Volume Stress 

Volume stress is also known as Bulk Stress. The term “volume stress” refers to stress that causes the body’s volume to fluctuate. Normal stress causes a change in length or volume, while tangential stress causes a change in the shape of the body, which is referred to as volume stress. When a body is submerged in a liquid and is under the force of pressure p, the body encounters a force that is perpendicular to the body’s surface.

Formula of Volume Stress

Volume Stress = Force / Area 

Shearing Stress 

A force applied tangentially across the plane’s surface area is known as shearing stress. When the forces operating on the surface are parallel to it and the stress acting on the surface traces a tangent, the surface is said to be tangent. Shearing stress is the term for this type of anxiety.

Formula of Shearing Stress

Shearing Stress = Force / Surface Area

Tensile Stress 

Tensile stress is defined as stress that occurs when a deforming force or applied force causes an increase in the object’s length. When a rod or wire is stretched, for example, equal and opposite forces (outwards) are applied at both ends.

Compression Stress 

The shape and volume of the body are altered when a tangential force is applied to it. The length of the body is reduced once compression load has been applied. Tensile stress and compression stress are diametrically opposed. Compression stress is created when you squeeze a pet’s squeak toy in your hand.

Hydraulic Stress 

The internal force per unit area acting on liquids is referred to as hydraulic stress. When a force is applied to the body by a fluid, hydraulic stress is the restoring force per unit area. Stress differs from pressure in that it considers the internal force per unit area rather than the outward force per unit area. Hydraulic stress is characterized in a similar way in the case of liquids. 

Radial Stress 

The radial stress is calculated for a thick-walled cylinder with a gauge pressure on the inside surface that is equal to and opposite the gauge pressure on the outside surface and zeroes on the outer surface. Because circumferential and longitudinal stresses are greater than radial stress, the latter is ignored.

Internal force is defined by stress, which is a physical quantity. The force across a “small” boundary per unit area of that boundary is defined as the stress. Stress, like velocity and torque, is a fundamental quantity (energy). One question that comes to me is which things are stress-worthy and which are not. You’ve probably seen that certain objects, such as rubber, can be easily stretched. In other words, when a stretching force (Tensile Force) is applied to any object, we can explain it. It will grow. A rubber band, for example, can easily stretch. On a rubber object, a tensile force is applied. Can you, however, stretch an iron rod? Because no tensile force is applied to the iron rod, the answer is no.

Stress is a macroscopic term, and there are some basic axioms of continuum mechanics. The particles used in its description and analysis should be small enough to work as homogeneous in formation and state, but large enough to neglect quantum effects and molecular motions. As a result, the force between two particles is the average of a large number of atomic forces between their molecules; and in physical measures, such as mass, velocity, and forces, it operates through the bulk of three-dimensional bodies and is supposed to be uniformly distributed over them.

Let’s look at an example to illustrate this point: Take a rubber pipe and an iron rod, and a square object to hang on the rubber pipe and iron rod. Wait a few moments, then pull both things together. The first object has Tensile Force, whereas the second object has not.

The classification of the internal distribution of internal forces in solid objects is covered by stress analysis, which is a branch of applied physics. Studying and designing structures such as dams, structural frames, tunnels, and mechanical elements under specified or expected stresses is a significant part of engineering. It is also necessary for many other disciplines, such as geology, where it is necessary to study ideas such as plate tectonics, volcanism, avalanches, and biology, where it is necessary to comprehend the anatomy of living beings.

Real-Life Example of Stress 

In architecture, the idea of stress is utilized to plan a building’s structure. The concept of stress and how it affects the different components of the building is integrated into everything from the foundations to the support beams to the columns.

Summary 

Stress is defined as “The restoring force per unit area of the material”.

Formula of Stress,

Stress = Restoring force / Area of the material

Types of Stress 

  1. Normal Stress
  2. Longitudinal Stress
  3. Volume Stress
  4. Shearing Stress
  5. Tensile Stress
  6. Compression Stress
  7. Hydraulic Stress
  8. Radial Stress

Sample Questions

Question 1: What is the Stress?

Answer:

Stress is defined as “The restoring force per unit area of the material”.

Formula of Stress,

Stress = Restoring force / Area of the material

Question 2: Explain Shearing Stress.

Answer:

A force applied tangentially across the plane’s surface area is known as shearing stress. When the forces operating on the surface are parallel to it and the stress acting on the surface traces a tangent, the surface is said to be tangent. Shearing stress is the term for this type of anxiety.

Formula of Shearing Stress,

Shearing Stress = Force / Surface Area

Question 3: What is the deforming force’s effect?

Answer:

The object’s shape, volume, or size may be altered by the deforming force.

Question 4: Pulling on both ends of a rod stretches it out. Describe the rod’s stress.

Answer:

Tensile Stress

Question 5: What is the SI Unit of Stress?

Answer:

SI unit of Stress is Pascal or N/m2 or N/mm2.

Question 6: Find the stress of an item with a 60 Newtons (N) operating force and a 4 mm2 cross-section area.

Answer:

Given:

Restoring force = 60 N

Area of cross-section = 4 mm2

Stress = Restoring force / Area of the material

∴ Stress = 60 N / 4 × 10-6

∴ Stress = 15 × 106 Nm

Stress of an item is 15 × 106 Nm

Question 7: Explain Longitudinal Stress.

Answer:

Longitudinal stress is defined as when the length of the body changes due to normal stress.

Formula of Longitudinal Stress,

Longitudinal Stress = Deforming force / Cross-sectional Area

Longitudinal Stress stretches or compresses an object throughout its whole length. As a result, based on the direction of deforming force, it can be divided into two types – Tensile stress and Compressive stress

When a rod is stretched according to Newton’s third law of motion, tensile stress is visible. Tensile stress is commonly represented by a rubber band being stretched out. Compression is the polar opposite of tension. When it is acting on a rod that is pressed at both ends by opposing or equal forces. Compressive stress is what you get when you squeeze a rubber ball in your hands.


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