What is the term for the point at which elasticity is exceeded, leading to permanent deformation or failure?

What is the term for the point at which elasticity is exceeded, leading to permanent deformation or failure?

• A. Elastic Limit
• B. Plastic Region
• C. Yield Point
• D. Ultimate Strength

Answer: (C)

The point where elasticity ends and permanent, plastic deformation begins on the stress–strain response is the yield point. Up to this point, the material returns to its original shape when the load is removed. Once you cross the yield point, dislocations move and the material deforms permanently even after unloading. If you keep increasing the load, you can reach the ultimate strength and eventually fail, but the onset of permanent deformation itself is defined by the yield point.

The point where elasticity ends and permanent, plastic deformation begins on the stress–strain response is the yield point. Up to this point, the material returns to its original shape when the load is removed. Once you cross the yield point, dislocations move and the material deforms permanently even after unloading. If you keep increasing the load, you can reach the ultimate strength and eventually fail, but the onset of permanent deformation itself is defined by the yield point.