Prediction of fracture limits of IN625 alloy by coupling ductile damage models and anisotropic yielding functions with the classical Marciniak and Kuczyński model

The fracture forming limit diagram (FFLD) is gaining special attention in high strength materials where the necking tendency rarely occurs during sheet metal forming processes. In the present work, the classical Marciniak and Kuczyński (MK) model has been modified by coupling it with different ductile damage models (Cockcroft and Latham, Brozzo, Oyane, Ko, Oh, Rice and Tracey, McClintock and Clift) and anisotropic yielding functions (Hill 1948 and Barlat 1989) to predict the fracture limits of Inconel 625 (IN625) alloy at different temperatures. Firstly, uniaxial tensile testing has been conducted for the determination of important mechanical properties. Consequently, stretch forming experiments have been performed to analyze the forming limits of a material. It has been found that the safe and fracture forming limits of the material increased by approximately 17.26% and 22.22%, respectively, on increasing the temperature from 300 to 673 K. From the comparative analysis of different combinations of ductile damage models and yielding functions, the Cockcroft and Latham (C-L) damage model in combination with the Barlat 1989 yielding function helped in best predicting the theoretical FFLD as it displayed the least average root mean square error (RMSE) of 0.033. The other ductile damage models used for predicting the theoretical fracture limits displayed large error; hence, they should not be considered while designing a critical component in the manufacturing industry using IN625 alloy.