The Von Mises criterion is a theoretical approach used in engineering and materials science to predict the yielding of ductile materials under complex loading conditions. It states that yielding occurs when the distortion energy in a material reaches a critical level, which can be determined from uniaxial stress tests. This criterion helps engineers design structures that can withstand various forces without failing. In practical terms, the Von Mises stress is calculated from the principal stresses acting on a material. If the Von Mises stress exceeds the material's yield strength, it indicates that the material will likely deform plastically. This criterion is widely used in finite element analysis and structural design.