Gero Burghardt, Andrew Flórez and Georg Jacobs
Wear particles and contaminants are known to reduce lifetime of machine elements such as roller bearings. This can be avoided through fine filtration. However, oil filterability…
Abstract
Purpose
Wear particles and contaminants are known to reduce lifetime of machine elements such as roller bearings. This can be avoided through fine filtration. However, oil filterability can change in service, and in case of exceeding the maximum pressure at the filter, contaminated oil can flow through a bypass, threatening the function of the lubricated components. The purpose of this study is to provide a cost-efficient method to estimate the long-term oil fine filterability.
Design/methodology/approach
The estimation of long-term oil fine filterability takes place in two steps. In the first step, oil in its original condition is subjected to different stresses to reproduce changes experienced in service within a relatively short period of time. In the second step, the resulting oil is subjected to filterability tests. Existing test methods were adapted to produce realistic oil changes and deliver a realistic evaluation of filterability.
Findings
Oils produced using metal-catalyzed thermal-oxidative stresses and humid air are similar to real oil samples from the point of view of nuclear magnetic resonance oil analyses and filterability tests. Test conditions suitable for highly viscous gear oils were derived considering operation at low and high temperatures.
Originality/value
The test method provides an estimate of deterioration of oil filterability in service through a comparison between the filterability of oil in original condition and the filterability of an artificially produced oil.
Details
Keywords
Christopher Sous, Henrik Wünsch, Georg Jacobs and Christoph Broeckmann
The purpose of this paper is to investigate the applicability of the quadratic failure hypothesis (QFH) on journal bearings coated with a white metal sliding layer on the…
Abstract
Purpose
The purpose of this paper is to investigate the applicability of the quadratic failure hypothesis (QFH) on journal bearings coated with a white metal sliding layer on the prediction of safe and unsafe operating conditions. The hypothesis covers operation conditions under static and dynamical loading.
Design/methodology/approach
Material tests and elastohydrodynamic, as well as structural, simulations were conducted to provide the required input data for the failure hypothesis. Component samples were tested to verify the results of the QFH.
Findings
The load bearing capacity of journal bearings was analysed for different operating conditions by the use of the QFH. Results allow for the identification of critical and non-critical loading conditions and are in accordance with component test results.
Originality/value
Today’s design guidelines for journal bearings do not consider a multi-axial stress state and actual stress distribution. The applied hypothesis enables consideration of multiaxiality inside the sliding surface layer, as well as determining the location of bearing fatigue due to material overload.