Crystallographic orientation dependence of fatigue crack propagation in Fe-3%Si. Characteristics of crack propagation at an early stage under KI+KII mixed mode loading.

Abstract

Fatigue tests were performed under Mode I and Mode I + Mode II mixed mode loadings using Fe-3%Si coarse grain specimens. The direction of fatigue crack propagation was investigated by changing the crack angle and crystallographic orientation of a notched grain. It was revealed that in the grain whose crystallographic orientation was [001], the fatigue crack propagated in specific directions, showing an aligned chevron pattern. Considering the formation of the aligned chevron pattern, it was found that the crack propagated in the maximum tangential stress direction among these specific directions.