Evaluation of welded Bearings by Tailored Forming

Minjae Kim


For the extraction of resources in the mining sector, very large machines usually perform the work in quarries and pits, which require high-performance components. Due to the big dimensions of the bearing and the possible geographical distance from the production site to the place of use, delivery of a new bearing can take several weeks. This eliminates the need to completely remanufacture the entire rolling bearing, if only the damaged raceway has to be restored. Starting from a damaged bearing, a coating material with sufficient chemical and physical properties is applied to the damaged surface by means of plasma or laser powder cladding depending on the size of the damage. The surface is pre-machined to the nominal dimension and receives a heat treatment. It is followed with an incrementally forming process with a deep rolling tool, to produce the rolling bearing properties, smoothing of the surface and induce compressive residual stresses. Welding defects, like pores or cracks can lead to an early failure and no extension of the service life and therefore have to be avoided. Comparable investigations are carried out on a FE8 rolling bearing test rig with a standardized test procedure and compared to industrial bearings. Additional investigations of the joining zone on the raceway are carried out on a tribometer, since it is necessary to check the suitability of the repair materials on conventional bearing steels. To investigate the influenced of welding defects, the fatigue crack growth simulation model is developed. The first simulations with gas pores are carried out.

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