The investigation of reasonable range of initial load of low-cycle fatigue cropping for notched bars

Abstract

The low-cycle fatigue cropping (LCFC) method is a new separation method that has low active load and low energy waste. A crucial challenge for the LCFC is to determine the suitable range of initial load, which impacts the crack initiation and the cross-section quality. This work proposes a novel crack initiation model which considers cumulative plastic deformation, material mechanical properties, notch stress, and material microstructure, and has a simple form. The acoustic emission technique (AET) is used to prove the validity of the model. The finite element method (FEM) and Electron backscatter diffraction (EBSD) are used to assess the effect of various initial loads. A laser confocal microscopy is used to measure the arithmetic mean deviation of the crack initiation area. The validity of the crack initiation model is proven. The critical crack initiation load (CCIL) of 316L, AISI 304, Al 6061, 1045 steel, and 16Mn bar are 2.470 mm, 2.080 mm, 1.310 mm, 2.980 mm, and 2.950 mm, respectively. The reasonable ranges of initial load for 316L, AISI 304, Al 6061, 1045 steel, and 16Mn bar are obtained.