Study On Mechanical Fault Diagnosis Based On Ferrography

The continuity and automation of modern production proposes a higher requirement on the safe and reliable operation of machinery and equipment. Ferrography is a fault diagnostis method based on the analysis of wear particle. Wear particle is an information carrier in the process of frictional wear and an important judgment basis of wear mechanism. Wear particle is an output that is easily obtained to reflect the time-varying characteristics of tribological system. Thus, the analysis of wear particle is one of major jobs to determine the characteristics of friction pair. it is key to mechanical diagnosis technology that how to assure the nature, type, location, causes, extent and tendency of fault by combining wear particle and parts-tree.The paper includes the following parts:(1) Friction pairs are categorized by nature, and the relationship between the operation condition of friction pair and wear particle is studied. The processes of frictional wear of friction pairs are simulated by friction tests of friction pairs matched under different materials. Moreover, the generation of wear particle through three stages under varying load and speed conditions, and influences of working environments on wear particle and the reliability of friction pair are analyzed.(2) The relationship between formation mechanism, location, and forms of friction pair accidents, and quantity, size, shape, color, morphology and structure of the wear particles are analyzed. Furthermore, the relationship between wear particle and the surface of machine is also discussed.(3) The fault tree diagnosis method based on ferrography is studied. In the fault tree, different materials and types of abnormal wear particles are taken as basic events, the corresponding mechanical surface morphology is taken into account, and the relationship between abnormal wear particles and malfunctions is discussed.(4) To solve the problems of "single kind of wear particle to multiple malfunctions" and "single malfunction to multiple kinds of wear particles", subordinate relationship between wear particle and friction pairs is set up and expressed as fuzzy diagnosis formula. The formula serves as the foundation of VB-based fault diagnosis.(5) Friction fault tree is set up by analyzing the fault mechanism of friction pairs in typical mechaniacal equipments. The fuzzy diagnosis formula is obtained by an analysis of fault tree. Finally, The method is proved to be valid by analyzing samples from engineerings.