spaltest

Spaltest is a term used in materials science to describe a testing procedure aimed at evaluating a material's resistance to spallation under high-strain-rate loading. Spallation is the development of tensile stresses inside a solid caused by the reflection of a compressive stress wave from a free surface, often during impacts or explosions. The spaltest seeks to quantify the material's dynamic tensile strength, known as the spall strength, and to characterize failure modes such as crack nucleation and fracture.

Common implementations use high-strain-rate devices such as the split Hopkinson (Kolsky) bar, a plate-impact setup using a gas gun, or similar shock-loading arrangements. In a typical spaltest, a forward-going compressive wave is generated in a driver plate and launched into a target plate; a reflected tensile wave arrives at the back surface of the target and may cause spall damage when the tensile stress exceeds the material strength. Data are gathered from strain gauges on the bars, witness plates, and high-speed diagnostics; the spall strength is computed from the spall stress at the time of fracture.

Applications include assessment of armor steels, aerospace alloys, ceramics, and composite laminates where high-rate loads are expected. Spaltests inform material design, heat treatment, and protective coating development, as well as quality control for components exposed to impulsive loading. Limitations include discrepancies between dynamic and quasi-static properties, size effects, and material anisotropy.

See also: spallation, dynamic tensile strength, Hopkinson bar, plate impact testing.