Yield Stress

Yield stress is the minimum amount of force or pressure needed to cause a material to start permanently deforming or changing shape. Think of it as the point where a material stops bouncing back to its original shape after being stretched or pressed and begins to bend or stretch permanently. For example, when you pull on a soft metal rod gently, it might bend slightly but go back to shape; but after reaching the yield stress, it will bend permanently. It helps engineers understand how strong a material is before it starts to deform permanently under load.