Dynamic fracture characteristics of FeMoSiB amorphous alloy ribbons

Dynamic fracture characteristics have been observed and interpreted for FeMoSiB amorphous alloy ribbons. Crack branching and stress wave induced cracking is the main features of dynamic fracture. Branching of the main crack occurs at the critical stress intensity KIB at the crack tip. Plane strain fracture toughness KIc and KIB is determined to be 11 and 35 MPa m0.5, respectively. It is deduced that crack branching is the necessary condition for generation of a compressive longitudinal wave for FeMoSiB amorphous ribbons. Stress wave induced cracking occurs when the amplitude of the reflected compressive longitudinal wave reaches the tensile strength. The amplitude of the stress wave is estimated to be at least 1.1 GPa to induce cracks at the originating laser hole. The reason why the dynamic characteristics of amorphous alloy have not been observed before may be attributed to the small dimension and shape of past specimens.