Young's modulus

Young's modulus or Young modulus is a mechanical property that measures the stiffness of a solid material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material in the linear elasticity regime of a uniaxial deformation. Young's modulus is named after the 19th-century British scientist Thomas Young. However, the concept was developed in 1727 by Leonhard Euler, and the first experiments that used the concept of Young's modulus in its current form were performed by the Italian scientist Giordano Riccati in 1782, pre-dating Young's work by 25 years. The term modulus is derived from the Latin root term modus which means measure. A solid material will undergo elastic deformation when a small load is applied to it in compression or extension. Elastic deformation is reversible (the material returns to its original shape after the load is removed). At near-zero stress and strain, the stress–strain curve is linear, and the relationship between stress and strain is described by Hooke's law that states stress is proportional to strain. The coefficient of proportionality is Young's modulus. The higher the modulus, the more stress is needed to create the same amount of strain; an idealized rigid body would have an infinite Young's modulus. Not many materials are linear and elastic beyond a small amount of deformation. E = σ ϵ {displaystyle E={frac {sigma }{epsilon }}} , where Both E {displaystyle E} and σ {displaystyle sigma } have units of pressure, while ϵ {displaystyle epsilon } is dimensionless. Young's moduli are typically so large that they are expressed not in pascals but in megapascals (MPa or N/mm2) or gigapascals (GPa or kN/mm2).