Fillet optimization on impact piston

Abstract: At Örebro University, a part of the Bachelor of Science in Mechanical Engineering, a degree project of 15 credits is to be made at the end of the education. This project can be performed at the university or at a company, and the purpose is to prepare the student for the upcoming employment after examination. This degree project were performed by Emil Tjus and Henrik Gustafsson during the spring of 2013 at Atlas Copco Rock Drills AB in Örebro on the department of Applied Mechanics. The subject of this project was to configure and execute an optimization of a fillet on an impact piston from Atlas Copco Rock Drills AB. The reason to optimize the fillet were founded in the wish to increase the fatigue lifetime of the impact piston. The optimization was performed in HyperWorks 12.0, a software that the department of Applied Mechanics not normally uses. This caused finite element models from previous work to be converted and evaluated to ensure that the models were correct configured in HyperWorks. The steps that was taken in HyperWorks towards an optimization were done by setting up an approach called Design Of Experiments. The results were then evaluated in the next step, an approach called Fit. After this step, an approach called Optimization were run to generate specific design parameters with the lowest possible stress range of the model. These parameters were then applied to a finite element model and an analysis was made to verify the result from the optimization. The results of the optimization lowered the total stress range in a fictitious impact piston from 1146,1 MPa to 717,4 MPa. This result was to be compared with the reference value of 604,7 MPa and the reference impact piston had a simple radial fillet. The result of this project did not yield any improvements of the impact piston. However, an optimization of the fillet was configured and completed in HyperWorks and this can hopefully be at use in future analysis.