Types Of Stress And Strain Pdf
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These forces are called stress.
Book on Mechanics of Materials(Simple Stress and Strain)
In continuum mechanics , stress is a physical quantity that expresses the internal forces that neighbouring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material. For example, when a solid vertical bar is supporting an overhead weight , each particle in the bar pushes on the particles immediately below it. When a liquid is in a closed container under pressure , each particle gets pushed against by all the surrounding particles. The container walls and the pressure -inducing surface such as a piston push against them in Newtonian reaction. These macroscopic forces are actually the net result of a very large number of intermolecular forces and collisions between the particles in those molecules. Strain inside a material may arise by various mechanisms, such as stress as applied by external forces to the bulk material like gravity or to its surface like contact forces , external pressure, or friction.
In psychology , stress is a feeling of emotional strain and pressure. Small amounts of stress may be desired, beneficial, and even healthy. Positive stress helps improve athletic performance. It also plays a factor in motivation , adaptation, and reaction to the environment. Excessive amounts of stress, however, may lead to bodily harm.
Three types of stress
A model of a rigid body is an idealized example of an object that does not deform under the actions of external forces. It is very useful when analyzing mechanical systems—and many physical objects are indeed rigid to a great extent. The extent to which an object can be perceived as rigid depends on the physical properties of the material from which it is made. For example, a ping-pong ball made of plastic is brittle, and a tennis ball made of rubber is elastic when acted upon by squashing forces. However, under other circumstances, both a ping-pong ball and a tennis ball may bounce well as rigid bodies. Similarly, someone who designs prosthetic limbs may be able to approximate the mechanics of human limbs by modeling them as rigid bodies; however, the actual combination of bones and tissues is an elastic medium.
In this article, we discuss three types of stress: Acute stress, episodic acute stress, and chronic stress. First responders can, and often do, experience all three. Stress can impact firefighter situational awareness and, equally concerning, stress can have devastating long-term impacts. As I was writing this article I recalled various times during my thirty years on the line where stress impacted my performance and my well-being. Responders are generally aware of the stresses that come from doing this job.
The Tensile stress is like pulling the material on each side or might one side as figures shown below,. The Compressive stress is like pushing the material on each side or might one side as figures shown below,.