What does the Poisson effect describe in materials?

The Poisson effect specifically describes the phenomena observed in materials where an applied tensile or compressive stress causes a change in dimension in the lateral direction, in addition to the longitudinal direction. It quantitatively illustrates the relationship between lateral strain and longitudinal strain, typically expressed as a ratio known as Poisson's ratio.

When a material is stretched in one direction (longitudinal strain), it will tend to contract in the perpendicular directions (lateral strain). This relationship is vital in engineering and materials science because it helps predict how materials will behave under different types of loading, ensuring that designs account for these dimensional changes.

Understanding the Poisson effect is critical for applications that involve deformation under stress, as it directly influences factors such as stability and strength when materials are used in structural components.