Performance Analysis And Wear Monitoring Method Of Linear-reciprocating Elastomeric Seal In Hydraulic Cylinder

Hydraulic linear-reciprocating elastomeric seals are a class of sealing components for hydraulic cylinder made of elastic polymers or thermoplastic materials,which play a vital role in ensuring safety and efficiency of hydraulic cylinders.The performance deterioration of seal directly affects the efficiency of the hydraulic cylinder,which not only increases the maintenance cost and pollution risk of enterprises,but also could lead to fateful incidents.Therefore,studying the lubrication and sealing mechanism of hydraulic linear-reciprocating elastomeric seals and to carrying out research on the characteristics of sealing structures are helpful for exploitation and further improvement of fault diagnosis and condition monitoring of hydraulic seals and significant both on theory and on practice for assurance of operational reliability,safety and stability during actual working process of hydraulic cylinders.In this thesis,research into performance analysis and monitoring method of hydraulic linearreciprocating elastomeric seal is conducted via theoretical study and experimental validation,with Y-shaped rod seal as research objective.Another important task is to explore innovative tools and solutions for seal wear monitoring.The principal works of the thesis are outlined below.(1)Based on the improved parallel plate model,the static leakage model of hydraulic linear-reciprocating elastomeric seal is established,and the procedures of pre-compression and self-energized of Y-ring were simulated by ANSYS.On the basis of obtaining the contact pressure distribution within the sealing zone,the G-W contact model and differential parallel plate model are combined to analyze the micro-interface lubrication state.The analysis method is carried out to study the influence of oil pressure,ambient temperature,attrition of sealing lip and surface roughness on the leakage rate of the Y-ring,which has unique advantage in static performance evaluation and failure prediction of elastomeric seal.(2)Based on Inverse Hydrodynamic Lubrication(IHL),a mixed lubrication model for hydraulic reciprocating seal is established.The lubrication model integrates the solid mechanics analysis between the Y-ring and the structure of sealing groove,the fluid mechanics analysis based on the Reynolds equation,the inlet hydrodynamic correction and asperity contact mechanics analysis of contact zone.three key influencing factors are studied through numerical calculation,among which are reciprocating speed,oil pressure and surface roughness.The change laws of sealing performance indicators such as contact pressure distribution,film thickness distribution,leakage and friction force of seal are compared and analyzed,revealing the mixed lubrication mechanism of reciprocating seal and realizing the characterization and prediction of dynamic sealing performance in working condition.(3)Research on the wear monitoring method of seal based on surface contact stress is conducted.The stress analysis of the sealing structure proves the feasibility of monitoring the wear degree of seal with the contact stress on sealing groove surface,and a sensor monitoring unit using fiber Bragg grating sensors is designed according to the analysis results.Furthermore,a monitoring test of seal wear is carried out to verify the effectiveness of the monitoring strategy based on FBG on wear monitoring on elastomeric seal,and a condition monitoring procedure is built for linearreciprocating elastomeric seal in hydraulic cylinder.