A new mixed mode I/II fracture test specimen: Numerical and experimental studies

This paper suggests a new test configuration, namely the disc bend (DB) specimen, for determining mode I, mixed mode I/II and mode II fracture toughness of brittle materials. The proposed specimen is a disc-type one containing an edge crack, which is subjected to three-point bend loading. The stress intensity factors, KI and KII, were obtained by performing many three-dimensional finite element analyses on the suggested DB specimen with different geometrical parameters and loading conditions. Based on the numerical analyses, different loading conditions from pure mode I to pure mode II can be produced by changing the crack distance from the middle point of the DB specimen. Finally, applicability of the proposed DB specimen was studied from the experimental point of view. For this purpose, several fracture experiments were successfully conducted on the white marble rock and PMMA (polymethylmethacrylate) materials under different loading modes.