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Critique of a Published Journal Article of Finite Element Method

INTRODUCTION

Roque (2000) has performed a simulation using the finite element method for cold forging of a ring of material DIN 16MnCr5. Software application used is ANSYS. The upsetting process was modelled using algorithms developed from previous research. The goal of the paper was to understand the material flow and the potential for die filling so that better parts can be produced. While upset forging is a common process, much of the die design is based on experience of the die designer and there are some inherent problems with the forging process and this results in small defects and a higher skin formation and excess allowance for machining. Chances of component rejection are higher as the material flow due to friction in the mould space depends on a number of uncontrolled variables and the actual manufacturing process is trial and error. By carrying out a simulation of the forging process, the author shows that end quality of the component can be predicted and controlled.

ANALYSIS OF THE METHOD USED BY THE AUTHOR

Roque (2000) has defined the problem statement by specifying a number of key parameters and a formed a differential equation that had to be solved using FEM simulation. A flow chart was created to depict the FEM method and the flow chart represented important nodes of the forging process. Table 1 gives the constitutive equations of plasticity and equations such as the stress strain relation yield function, flow and hardening rules and the Kuhn-Tucker conditions were fed into the applications. A number of equations were used to set the contact conditions for metal forming analysis and to calculate the stress and internal variables, the radial return mapping algorithm was used. Among other methods that were used was the penalty method to place the contact conditions between the die, tool and the billet surfaces.

Another aspect that has not been considered is the relation of the forging pressure applied. While the Youngs Modulus of the billet material is given, there is no mention of how much pressure was applied during the pressure and if increasing the pressure would cause material to flow more faster and the effect of increased pressure on the defects and discontinuities (ASM, 2005).

FINAL COMMENTS AND CONCLUSIONS

ANSYS is a very powerful software application and all the issues mentioned above could have been answered with the proper simulation techniques. By performing the operations mentioned in the previous section, the simulation would have had more value that is practical. As such, the paper has just mentioned how simulation using FEM can be performed using the methods mentioned. The author should have at least provided section that explained these shortcomings and suggested these studies as areas for further research.

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