# What Are the Mechanical Properties of Mild Steel?

Mild steel has a yield strength of 60,200 pounds per square inch (psi), a tensile strength of 78,300 psi, a modulus of elasticity of 29,000 psi, and a Poisson's ratio of 0.29.

The yield strength of a material is the stress at which plastic deformation of the material begins to take place. Plastic deformation occurs at stresses higher than stresses that cause elastic deformation, and plastic deformation is generally irreversible, unlike elastic deformation. The tensile strength of a material is the maximum stress that can be applied to a material in a tensile test before the material fails (breaks). The modulus of elasticity, also known as the elastic modulus or Young's Modulus, of a material (in particular a metal or other elastic material) is the ratio of linear stress to linear strain in the material when the material is subjected to an external load. The modulus of elasticity is a measure of the general stiffness of the material. The Poisson's ratio of a material is the ratio of the contraction at right angles to an applied stress to the material and the extension of the material in the direction of the applied stress. When an axial stress is applied to a material, the material tends to extend in the axial direction and contract in the other two directions. The ratio of one of these contractions to the axial extension is Poisson's ratio.