Modulus of elasticity, also known as elastic modulus or Young’s Modulus, is a measure of how a material or structure will deform and strain when placed under stress. Materials deform differently when loads and stresses are applied, and the relationship between stress and strain typically varies. The ability of matter to resist or transmit stress is important, and this property is often used to determine if a particular material is suitable for a specific purpose.
This property is often determined in a laboratory, using an experimental technique known as tensile testing, which is usually conducted on a sample of material with a specific shape and dimensions. There are a variety of testing devices available that apply very precise loads and stresses to the sample, and accurately measure and record any resulting strain in the material. The modulus of elasticity is known for a wide variety of structural materials, including metals, wood, glass, rubber, ceramics, concrete, and plastics.
The modulus of elasticity describes the relationship between the stress applied to a material and its corresponding strain. Stress is defined as a force applied over a unit area, with typical units of pounds per square inch (psi) or Newtons per square meter — also known as pascals (Pa). Strain is a measure of the amount that a material deforms when stress is applied and is calculated by measuring the amount of deformation when under stress, as compared to the matter's original dimensions. Modulus of elasticity is based on Hooke’s Law of elasticity and can be calculated by dividing the stress by the strain.
For many materials at low levels of stress and under tension, the stress and strain are proportional — meaning they increase and decrease in a constant way, relative to each other. Deformation of a material that occurs when the stress and strain behave proportionally is known as elastic deformation or elastic strain. Modulus of elasticity describes the relationship between stress and strain when under these conditions.
Elasticity is the ability of a material to return to its original state or dimensions after a load, or stress, is removed. Elastic strain is reversible, meaning the strain will disappear after the stress is removed and the material will return to its original state. Materials that are exposed to intense levels of stress may deform to the point where the stress and strain no longer behave proportionally, and the material will not return to its original dimensions. This is referred to as plastic deformation or plastic strain.