Physics-of-failure models of erosion wear in electrohydraulic servovalve, and erosion wear life prediction method

A series of Physics-of-Failure (PoF) models for particle erosion wear of electrohydraulic servovalves (EHSV), and the PoF based erosion wear service life prediction models, are established. Because there are only few correlative quantitative researches on the effect of erosion wear to EHSV, establishing the PoF models is of great significance to solve the problem. These models can also help to design a high-reliability and long-life EHSV, to establish relevant specifications, or to carry out accelerate life tests of EHSV. Before modeling, this paper analyzed the failure mechanism; and deduced mathematical models of servovalve’s critical performance parameters (CPP) that involved in the Slide Valve’s pressure gain, null leakage flow, and the Flapper nozzle Valve’s null bias, which may be affected by particle erosion wear. The factors that influence servovalves lifetime are the hardness, shape and size, velocity, concentration of particle, the design and assembling parameters, and the application method. With erosion wear equations, we connect the factors to mathematical models of CPP to establish the PoF models. The methods to ascertain parameters in the models are proposed. Contaminant erosion wear experiments are carried out at fluid cleanliness level 7. The results show the PoF models can be utilized to precisely describe the degradation process and accurately estimate the erosion wear life of various servovalves.