What does the modulus of resilience Ur represent?

• A. Energy absorbed during elastic deformation
• B. Energy absorbed during plastic deformation
• C. Area under the plastic portion of the stress-strain curve
• D. Elastic modulus

Answer: (B)

Modulus of resilience is the energy per unit volume that a material can store elastically, i.e., recoverable energy when loaded within the elastic limit. It corresponds to the area under the elastic portion of the stress–strain curve, up to the yield point. For linear-elastic materials, this energy can be written as Ur = (1/2) * sigma_y * epsilon_y = sigma_y^2 /(2E). This is not the energy absorbed during plastic deformation (that’s the plastic work), nor the area under the plastic portion. It’s also not the elastic modulus, which measures stiffness, not energy storage.