Which statement differentiates modulus of toughness from impact toughness and names the tests used to measure each?

Which statement differentiates modulus of toughness from impact toughness and names the tests used to measure each?

• A. Modulus of toughness is a measure of hardness.
• B. Modulus of toughness is the area under the stress–strain curve; impact toughness is energy absorbed in a high‑rate impact.
• C. Impact toughness is the area under the stress–strain curve.
• D. Modulus of toughness is energy absorbed to fracture (area under the stress–strain curve); impact toughness measures energy absorbed in a high-rate impact (Charpy or Izod tests).

Answer: (D)

Toughness has two aspects: the energy a material can absorb as it deforms up to fracture, and the energy it can absorb under a sudden, high-rate impact. The first is read from the tensile stress–strain curve as the area under the curve up to fracture, which represents the material’s resistance to fracture under slow loading. The second is about impact resistance, measured when a sample is struck quickly and energy is absorbed in a short time; this is quantified in pendulum impact tests like Charpy or Izod. So the best statement ties modulus of toughness to the energy absorbed to fracture (the area under the stress–strain curve) and identifies impact toughness as the energy absorbed in a high-rate impact, measured by Charpy or Izod tests. The other options either misstate toughness as hardness, or swap the definitions (impacts not represented by the area under the curve), or omit the standard test names.

Toughness has two aspects: the energy a material can absorb as it deforms up to fracture, and the energy it can absorb under a sudden, high-rate impact. The first is read from the tensile stress–strain curve as the area under the curve up to fracture, which represents the material’s resistance to fracture under slow loading. The second is about impact resistance, measured when a sample is struck quickly and energy is absorbed in a short time; this is quantified in pendulum impact tests like Charpy or Izod.

So the best statement ties modulus of toughness to the energy absorbed to fracture (the area under the stress–strain curve) and identifies impact toughness as the energy absorbed in a high-rate impact, measured by Charpy or Izod tests. The other options either misstate toughness as hardness, or swap the definitions (impacts not represented by the area under the curve), or omit the standard test names.