Dynamic hardness testing
Dynamic hardness testing measures a material's hardness by striking it with a body of known energy. The rebound distance indicates how much energy was absorbed.
Physical-Chemical Mechanism of Action
Dynamic hardness testing is based on the principle of a heavy body (e.g., a ball) impacting the surface to be tested. The energy with which the body strikes is converted into work as it rebounds. The rebound distance is a measure of the absorbed energy and thus the hardness of the material.
Metallurgical Relevance & Welding Risks
Dynamic hardness testing is especially important for high-hardness steels, such as martensitic or tempered steels. If the martensite content is too high, dynamic hardness can increase sharply, leading to more crack-sensitive weld areas. A too-high dynamic hardness level can also impair the toughness and ductility of the material.
Workshop Practice & Instructions
To perform an accurate dynamic hardness test, the body (e.g., a ball) should fall onto the surface to be tested with a defined speed. The drop height determines the kinetic energy. The rebound distance is measured and converted into a hardness value. A typical standard for the drop height range is between 50 mm and 100 mm. For steels with high martensite content, dynamic hardness should not exceed 600 HV to avoid cracking.