Abstract: Powder compaction in mold is an important industrial forming method that increases energy efficiency, saves time and cost and thus increases production rates. In the present study, the metal powders compaction process Ag35Cu32Zn33 is simulated using the finite element method in order to calculate the distribution of stress and strain in the compacted parts and the mold. The most challenging step with regard to the simulation is to select the appropriate constitutive model for the powder plastic deformation, the unknown constants of which can be calculated easily and accurately by performing calibration tests. Here, the density-dependent generalized Drucker Prager Cap (DPC) model is used to predict the plastic deformation of refractory powders, which according to the European unio‎n of Powder Metallurgy has the best performance among the existing constitutive models. The model parameters including the coefficients of elasticity, yield surface, shear failure surface and friction in different powder densities are measured experimentally from the combination of the instrumented cylindrical die compaction test the uniaxial and diametrical strength test. The density dependence of the model parameters is defined by a USDFLD subroutine in Abaqus software. The simulation results are in good agreement with the results published in the literature. According to the results, a nonhomogeneous distribution of the relative density and stress is created in the powder during loading and unloading, which is dependent on the friction coefficient between the powder and the die. The friction coefficient has a greater effect on the stress magnitude in the powder and the die than the material properties of the die, and the maximum stress in the powder occurs in the areas adjacent to the upper mandrel and the die wall. With increasing the friction, the average relative density of the powder decreases and the pressure required for compaction and the stress in the powder and die increases. The stress values created in the die are in the elastic region, and they decrease by 35% in the unloading stage compared to the final stage of compaction. The die fatigue life prediction is done by importing the stress results of the cylindrical die in Fe-safe software, defining the loading cycle and assigning fatigue properties for different die materials. The results of the stress-life and the strain-life models taking into account the effect of multiaxial stress, the mean stress, and the actual working conditions of the die in industrial workshops showed that dies made of SAE4340 have a higher fatigue life than SKD11 and CK45. Also, increasing the thickness of the die wall significantly increases the fatigue life of the die. So that by increasing the thickness of the die made of SAE4340 and CK45 from 2.5 to 5 mm, no fatigue damage occurs. The results of this study lead to an increase in the quality of products, improve the design of the mold and the correct choice of its material as well as prevent the damage that is imposed on industrial sectors in this area as a result of improper mold design.

محمد خدائي

محمد خدائي