BEASY Projects: WestLand

Computational Mechanics participated in a collaborative research project with GKN Westland Helicopter, Rolls Royce, Imperial College, and Nottingham University. The objective of this project was to develop a robust computer-based design tool for spline joints commonly used in gas turbine engines and helicopter transmissions. The new state-of-the-art computer code will allow designers to simulate the contact stress between the spline components. The computer code is capable of simulating the contact problems including where friction acts on the contact surfaces. A simple fretting wear model has also been incorporated into the software.

Experimental testing, including extensive strain gage measurements and photo-elastic modelling were carried out to validate the computer modelling. Testing work included the use of a variety of testing machines. These include a high frequency reciprocating test rig with one optically transparent contact surface and a 3-tooth quasi-dynamic spline test rig. These testing machines are designed to investigate the mechanisms of fretting wear initiation and progression. The fretting studies in which specimens are designed to simulate the contact of a pair of spline teeth have been conducted to investigate the effect of a wide range of variables. These variables include material, heat treatment, coating, machining process (grinding, shaping, broaching), reciprocating amplitude, contact pressure, temperature, and type of lubrication.

This new software tool will have great impact on the design community because important maintenance and failure issues can be addressed during the conceptual design phase without costly experiments. Design to avoid wear and optimise maximum load carry capacity will now be possible.