A simplified method for measuring plane strain fracture toughness

A fracture toughness measuring concept is presented which is based on the use of specimen configurations for which the initial crack growth is stable under controlled force (“soft” machine) conditions. The concept is analyzed, and is demonstrated on a specimen configuration consisting of a short rod with narrow longitudinal slots for crack guides. Tests were conducted on two types of aluminum, PMMA, fused quartz and siltstone rock. It is shown that the fracture toughness test is very simple to perform, gives repeatable results, and is equally applicable to both ductile and brittle materials.