Tool Life Simulation of Femoral Stem Hip Arthroplasty Hot Forging Dies

The femoral stem is part of an artificial hip joint arthroplasty that is installed through surgical procedures to replace the problematic hip in the patient. The femoral stem part was manufactured using a hot forging process. Even though the forging die material was selected from hot working tool steel, the changes in the die geometry outside die closure tolerance may have occurred after numerous forging cycles. This can lead to defective femoral stem products. A simulation using ANSYS LS Dyna was performed in this research to determine the tool's life. The simulated forging pressure of 250 tons and loading speed of 300 mm/s were applied on two different workpieces of AISI 316L plates and Ti6Al4V bar. The simulation provides maximum equivalent stress and total deformation of the workpieces. Archard Wear Equation was then utilized to calculate the total wear per cycle of the forging dies based on those data. This tool’s life in terms of the maximum number of cycles of the dies was determined by dividing the die closure tolerance database in the ASTM-A521 standard by the total wear per cycle. The results show that the tool life of 6210 cycles was found for AISI 316L plate workpieces of 12 mm thickness and 3899 forging cycles for Ti6Al4V bar of 24 mm diameter. This condition happened because a lower flashing area was being generated, which led to less wear on the die trim line with the smallest plate thickness or bar diameter. Meanwhile, for other dimensions of plates and bars, a lower tool life was estimated before the dies were unusable.