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Toughness is a material property that describes its ability to absorb energy and plastically deform without fracturing. It combines both strength and ductility, making it a critical characteristic for materials that will experience impact or dynamic loading.

Charpy impact strength is specifically designed to measure this toughness by evaluating how much energy a material can absorb during fracture when subjected to a sudden load. In a Charpy test, a notched specimen is broken by a swinging pendulum, and the energy absorbed in the fracture process is recorded. A higher Charpy impact strength indicates a tougher material, capable of withstanding greater impact forces before failing.

In contrast, yield strength primarily indicates the stress at which a material begins to deform plastically. Ultimate tensile strength measures the maximum stress a material can withstand while being stretched or pulled before necking occurs. The fatigue limit evaluates the maximum stress level a material can endure for an infinite number of load cycles without failing. While these properties provide valuable information about a material's performance under various loading conditions, they do not directly measure toughness in the same way the Charpy impact strength does.