12.7:
Stress
A change in the shape of an object due to an applied force is known as deformation. Squeezing, twisting, squashing, or pulling the object apart are some examples of deformations.
Let us consider a wooden plank of length L. When a force is applied on the top surface of the plank in a downward direction, the plank undergoes deformation. The magnitude of the applied force per unit area is called stress.
The SI unit of stress is the pascal and is defined as the force of one newton exerted over a unit surface area of one meter squared.
Stress can be categorized as tensile stress, compressive stress, volume stress, and shear stress.
When the deforming force on an object results in an increase or a decrease in the object's length, it is termed as tensile or compressive stress, respectively.
Whereas, if the volume of an object changes due to the deforming force, it is termed as volume stress. If the direction of the deforming force is parallel to the cross-sectional area, it is called shear stress.
12.7:
Stress
When a force is applied on a body, it undergoes deformation. In order to restore the body to its original shape and/or size, an opposite or restoring force is generated within the body. This restoring force is equal to the magnitude of the applied force, but acts in the opposite direction. The amount of this restoring force developed per unit area of the body is called stress. Stress is a tensor quantity and has the SI unit pascal. Stress can be separated into four broad categories depending upon the direction of the forces acting on the body and the type of deformation the body undergoes. These include tensile stress, compressive stress, volumetric stress, and shear stress.
When the force applied to a body results in an increase or decrease in the body length, the resulting stress is termed as tensile or compressive stress, respectively. If the applied force acts on all the sides or dimensions of a body and results in a volume change, it is known as volumetric stress. If the direction of the applied force is parallel to the cross-sectional area and results in a change in the shape of a body, it is termed shear stress.
This text is adapted from Openstax, University Physics Volume 1, Section 12.3: Stress, Strain, and Elastic Modulus.