Elasticity is a mechanical property that describes a material’s ability to deform under an applied load and return to its original shape once the load is removed. Elastic behavior occurs when the material is stressed within its elastic region, meaning the deformation is temporary and reversible. The relationship between stress and strain in this range is governed by Hooke’s Law:
stress = modulus of elasticity × strain or σ = E × ε,
where E (Young’s modulus) is the material’s stiffness, a measure of its resistance to elastic deformation.
Key Characteristics of Elasticity
- Proportionality
- In the elastic region, stress and strain are proportional, resulting in a linear relationship on a stress-strain diagram.
- The slope of this linear region corresponds to Young’s modulus, with higher values indicating stiffer materials.
- Elastic Limit
- Elastic behavior ceases at the elastic limit, the maximum stress at which the material can return to its original shape. Beyond this point, plastic deformation occurs.
- Material Dependence
- Metals (e.g., steel, aluminum) and ceramics exhibit high elasticity due to their strong atomic bonds.
- Polymers and rubbers exhibit significant elastic deformation but lower stiffness, meaning they stretch easily compared to metals.
Types of Elasticity
- Linear Elasticity
- Exhibited by most materials within their elastic limit. The stress-strain curve is a straight line, and deformation is small.
- Nonlinear Elasticity
- Some materials, such as polymers, exhibit a curved stress-strain relationship but still return to their original shape if the elastic limit is not exceeded.