Fatigue Crack-macrocrack Interaction in 316 Stainless Steel Sheet

Abstract

Defects are introduced in engineering materials during various stages of metal extraction, processing and fabrication. Defects are also introduced to fulfil certain engineering requirement and also during services. A growing fatigue crack is likely to interact with these material discontinuities. The presence of these defects may alter the stress field, crack growth rate and also deflect the crack path. The aim of this investigation is to study the interaction of a growing crack emanating from the semi-circular hole and a macrocrack in 316 stainless steel sheet. The study has been conducted to analyses the effect of macrocrack size, orientation and position on the fatigue crack path and crack growth rate. The study has been made using side edge notch specimens of 125 mm×70 mm size from a 316 Stainless Steel sheet of a 2 mm thick thickness. Experimental specimens were fabricated by wire EDM and notch were created at the position of macrocrack. All experimental tests were conducted using a 100 kN BiSS servohydraulic UTM. The monitoring of crack path was done by tip tracking method (TTM) using a high-resolution camera. The finite element analysis code FRANC2D has been used to calculate the stress intensity factors,stress field and crack path in the different configuration of macrocrack. It is interesting to observe that in all the cases the simulation technique has correctly predicted the crack path as observed by experimentation. In a few cases, the emergence of crack took place from the macro crack. It is also seen that stress field associated with the crack tip is the main reason to deflect the crack path and alter the crack growth rate.