Chapter 5: Case Study for Magnesium Alloy Sheets to Predict Ductile Fracture of Rotational Incremental Forming
In this study, to predict a fracture of rotational incremental forming for magnesium alloy sheet, the heat generation at elements due to rotational tool and contact area between the specimen and the tool was implemented using finite element simulations through Johnson-Cook model and then compared with experiments of the square shape with 45 degree, 60 degree, and 70 degree wall angles. Commercial software (ABAQUS version 6.5, explicit formulation) with a user-defined subroutine (VUMAT) based on a combined kinematic/isotropic hardening model was used for the simulation. The (FE) simulation results show that if the wall angles of 80 mm × 80 mm × 25mm square shape are smaller than 60 degree then the maximum value of the fracture ductile integral I will be less than 1 value, and fracture will not occur. The predictions of failure site were in good agreement with those in actual experiments. The (FLCF) prediction and effect of process parameters on (FLCF) utilized (FE) simulation results show that the formability decreases as the tool down-step or tool radius increase. This prediction is suitable to previous conclusion  of incremental sheet forming process.
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