What does a Charpy test measure?

What does a Charpy test measure?

• A. impact strength (notch toughness)
• B. hardness
• C. tensile strength
• D. fatigue life

Answer: (A)

Measuring a Charpy test focuses on how much energy a material can absorb before fracturing under a sudden impact, i.e., impact toughness (notch toughness). In this test, a notched specimen is mounted horizontally and struck by a swinging pendulum. The energy the specimen absorbs during fracture is inferred from the difference in the pendulum’s energy before and after impact, and is reported as energy in joules. The notch concentrates stress, so the result reflects how well the material resists rapid crack initiation and propagation under impact. Temperature effects are important, too—some materials become much more brittle at lower temperatures, which shows up as lower absorbed energy.

Hardness tests measure resistance to indentation, not impact energy. Tensile strength assesses the maximum stress under a slow, uniaxial load. Fatigue life evaluates how many cycles a material can endure under repeated loading before failure.