Reliability Modeling for Hydraulic Components of Heavy Duty Machine Tools Based on Degradation Path for Oil Contamination

The failures of heavy-duty machine tool was mainly on the hydraulic system and caused by oil contamination. Aim at the problem, the trend change test of oil contamination have been carried out. After the time domain analysis on test data of oil sample, the dimensional parameters of particle numbers was obtained. Through the analysis by Q-Q plot on dimensional parameters, it can be seen that the degradation data of contaminated particles obey the normal distribution. Hydraulic component was summarized into three categories, pipeline, valve and filter. The blockage of pipeline and valve was studied by the particle number about 5μm. The wear of pipeline and valve was studied by the particle number larger than 15μm. The blockage of filter was studied by particles with the similar filtering accuracy. The threshold of the particle number was set according to the 20/17 level of ISO4406 standard. Reliability models of various components for a single failure mode was established based on the degradation path. The reliability model under multiple failure modes was fused by the former model.