The consortium has carried out a state of the art analysis in regards to surface and heat treatments, coatings and fatigue mechanisms in spline connections. In this analysis, existing literature has been searched, reviewed and evaluated. IWT focused on the topic PVD solid lubrication, BIAS focused on the topic of laser structuring with the scope on tribology and WZL focused on topics of spline joint fretting-wear and -fatigue. Furthermore, a model of the spline connection concerning clearances, displacements and misalignments, friction and resulting pressure distribution has been implemented by WZL.
The consortium took different combinations of laser structuring combined with physical-vapour-deposition (PVD) into account to create new, durable spline surfaces. Simple specimen have been produced, to assess these different surface treatments and coatings. IWT applied different surface coatings onto the specimen and BIAS applied the foreseen laser structuring. Additionally, some specimen have been coated a second time before all specimen have been characterised. IWT has performed Pin-on-Disk tests with the manufactured specimen, to gain knowledge about the wear behaviour of the surface treatments under contact load.
WZL designed a spline coupling, suitable for full scale spline investigations. Based on the implemented FE-model and analytical calculations, the macro- and micro geometry of the spline joint has been optimised in order to meet the required contact pressure and sliding velocities in the tests. In addition, the required shaft misalignment and rotational speed for the investigations have been determined. The full scale splines have been manufactured and the spline shafts have been optimized with surface treatments in terms of PVD-coating and laser structuring systems. Finally, the splines have been characterized to document their pre-testing conditions.
A test bench has been designed to perform conclusive testing of the full scale splines. The developed test bench design is based on an extension of a back-to-back test bench according to DIN ISO 14635. For the extension, the spline-joint has been integrated into the shaft system and the dedicated spline misalignment has been applied.
The manufactured full scale splines have been tested on the newly developed test bench. For the testing, the to be tested variants with the concerning surface treatments have been used. To investigate the wear and fatigue behaviour of the different test variants, the full scale spline-joints have been investigated under the same test conditions for each test in terms of torque, rotational speed and dedicated angular misalignment. To compare the test variants, pre- and post-testing topography measurements have been used to evaluate the changes on the tooth flanks. With this data, the test variants have been compared to each other according to their operational behaviour.
