The effect of external dynamic loads on the lifetime of rolling element bearings: results of accelerated lifetime tests

Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasises an important influence of external dynamic loads on the lifetime of bearings. The loads can result from structural resonances, gear meshing, etc. Lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting their influence. Inaccurate estimations of the lifetime lead to excessive safety factors during design and unexpected failures during operation. This paper analyses the influence of external dynamic loads using a novel bearing test rig. The test rig allows applying static and dynamic loads on the test bearing in both the radial and axial direction. During dynamic excitation of the test bearing, increased frictional power loss is measured based on the bearing temperature. The measurements reveal the bearing operational conditions (static loads, dynamic loads and speed) at which wear due to external dynamic loads is expected to be maximal. Accelerated lifetime tests are afterwards performed in these conditions. The effect of radial, axial and combined radial and axial dynamic loads is separately investigated. Microscope images reveal the effect of dynamic loads on wear of the raceway surfaces.status: accepte