Materials Performance: Elasticity

Understanding Elasticity

Elasticity in materials is the ability to return to its original form after being deformed.
It refers to the material’s response to stress and strain, and is typically measured by the modulus of elasticity.
All materials have a degree of elasticity until they reach their elastic limit. Beyond this point, they will permanently deform.

A material is said to be in the elastic region if it returns to its original shape after the removal of stress.
Hooke’s Law: This law states that strain is directly proportional to stress until it reaches its elastic limit. Beyond this point, the relationship is not linear and the material deforms plastically.
Elastic Limit: The maximum amount of stress a material can withstand without undergoing permanent deformation.
Yield Point: The point of stress at which a material begins to deform plastically. It represents the limit of elastic behaviour.
Young’s modulus measures the stiffness of a solid material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material.

Rubber and elastomers have a high degree of elasticity, which allows them to be extensively deformed but revert back to their original shape.
Metals such as steel also possess good elasticity, especially beneficial in constructions to withstand varying loads.
Certain types of plastic, like polyethylene and polypropylene, exhibit substantial elasticity.

Generally, elasticity decreases with increasing temperature.
Thermal expansion refers to the increase in volume of a material when it is heated. It’s critical to consider this when designing products to ensure correct functioning during a range of temperatures.

Designers consider material’s elasticity when creating products that need to withstand strain and return to their original shape, such as springs, elastomer products like bicycle handles, and sports equipment like tennis racquets.
It is also important in the design of structures and buildings where deformation under load should be minimal.