A thermo-mechanical finite element simulation model to analyze bushing formation and drilling tool for friction drilling of difficult-to-machine materials

Abstract

In metallurgical view point, difficult-to-machine materials are named as materials which have high work-hardening, low thermal conductivity, and great toughness. Since recently special attention has been paid to the difficult-to-machine materials in different applications, an excellent potential for product fabrication is proposed by friction drilling. However, the main problem is encountered when friction drilling of difficult-to-machine materials are poor machining performance and short tool life. Due to the wide range of applications for difficult-to-machine materials AISI304, Ti-6Al-4 V, and Inconel718 in different industries, this paper is concerned with thermo-mechanical modelling of friction drilling process on these materials using drilling tool of WC which contributes to gain an in-depth understanding of how friction in workpiece-tool interface generates the heating. It can help to find out effects of frictional heat generation on bushing formation and drilling tool, and how to improve quality of bushing formation and prolong tool life. In order to verify the numerical simulated results and evaluation of surface quality and required thrust force, an experimental validation is also conducted. A comparison of the predicted and experimental results reveal that the main reasons of uniform bushing formation quality and low tool degradation for friction drilling of Inconel718, and non-uniform bushing formation quality and high tool degradation for friction drilling of Ti-6Al-4 V are high work hardening of Inconel718 and low thermal conductivity of Ti-6Al-4 V. Moreover, the bushing formation cycle time, where the maximum contact between drilling tool and bushing hole-wall occurs, is the most critical step time in friction drilling process that causes maximum tool wear.