High Interference Cold Expansion of Bushings Made From Copper-Beryllium Replacement "ToughMet 3" Alloy

Extra precautions required to safely machine copper-beryllium alloys has driven the aerospace industry to find a replacement material with similar properties for use as a high strength bushing and bearing material.  “ToughMet 3”, a Cu-15Ni-8Sn spinodal alloy is now successfully being used as an alternate alloy material. In service, it has shown to provide lower friction and increased wear resistance when compared to other copper based alloys used for bushings and bearings including copper beryllium. For high interference fit bushing installations, most aerospace companies use the ForceMate method to expand the bushing into a hole to create a high interference fit with a synergistic residual compressive stress around the hole. Fatigue Technology conducted a bushing removal force comparison between different bushing materials including copper beryllium (AMS 4533), 13-8 PH stainless steel (AMS 5629) and ToughMet 3 (AMS 4596).  ToughMet 3 had greater retention than copper beryllium and also had a higher retained expansion in the parent material.  This paper will discuss the evaluation and comparative test results between conventional shrink-fit and ForceMate installation methods for the different materials mentioned above along with FEA results of the retained expansion properties.  The results showed conclusively that the ToughMet 3 alloy can be installed with the ForceMate method and will meet or exceed retention properties of copper beryllium.