In mechanics of materials, an axial load applied to a bar induces not only longitudinal (axial) strain but also lateral (transverse) contraction or expansion; the ratio of transverse strain to axial strain, within the proportional limit, is a material constant called Poisson's ratio. Under pure shear loading, shear stress is likewise proportional to shear strain within the elastic limit, with the proportionality constant termed the shear modulus (or modulus of rigidity). Together with the direct relation between axial stress and strain (Hooke's Law), these constants allow strain in multiaxial and shear-loaded elastic bodies to be characterized and superposed.
In mechanics of materials, an axial load applied to a bar induces not only longitudinal (axial) strain but also lateral (transverse) contraction or expansion; the ratio of transverse strain to axial …