Experimental and numerical investigation of ductile fracture of K418 on in-situ tensile tests

In this study, the effect of the Lode angle on failure and plasticity is considered, and a new Lode angle function on plasticity is developed. Meanwhile, a new temperature coefficient function is proposed in this model, and the application of the model is extended to the range from room temperature to 650 degrees C. The tensile specimens of different shapes have been designed to calibrate the parameters of the model. The tensile tests are carried out on the in situ micro-tensile machine. For the notched tensile specimens at room temperature to validate the constitutive model, numerical results are consistent with experimental ones well, with an error of 7%. Then, the calibrated model is applied to FE simulations to numerically study the fracture phenomena observed in the test. The fracture positions and damage initiation positions of the shear specimen and the notched tensile specimen can be predicted by FE simulations well, while the smooth tensile specimen cannot be predicted well due to real specimens' imperfections. A coupled plasticity-damage model is proposed.A new Lode angle function and temperature coefficient function are developed.The experimental and numerical damage evolution and fracture edges are in agreement.