A fracture mechanics specimen and loading device for the determination of fracture toughness under superimposed normal and shear modes of loading

A simple compact fracture-mechanics specimen and a loading device are suggested for the determination of fracture toughness under loading mode I, loading mode II, and a mixed loading mode. All specimens are photoelastically tested, and the device is demonstrated by applying superimposed normal and shear modes to the specimens. Force is applied at 0 deg for pure traction, between 0 and 90 deg for superimposed loading, and at 90 deg for pure shearing force. The ratio of crack depth to sample width (a/w) is determined to be not less than 0.5, and the stress intensity factor for the proposed fracture-mechanics specimen is presented as a function of the load application angle and the ratio a/w.