Spalling Principle
A compressive stress wave in a body will reflect as a tension wave at a free boundary. If the tensile stress exceeds the material's strength, a fracture can occur - this is known as a spalling failure. The HPB can be used to load one end of long cylindrical specimen with a known compression wave. The far end of the specimen is unsupported, which causes the wave to reflect in tension and induce a spalling failure. This method is better suited to brittle materials such as rocks, ceramics or other materials where the tensile strength is lower than the compressive strength.
Schematic
