Study On Lubrication Condition Based On Acoustic Emission Technology

As an advanced nondestructive testing technique, acoustic emission(AE) technology is widely used among many engineering fields. In recent years, this technology has aroused extensive concern in tribology research areas because of its novel and unique characteristics. In internal combustion engine, the friction between cylinder liner and piston ring plays an important role for its performance and durability. Good lubrication condition can decrease friction force in tribological system, improve fuel efficiency, reduce energy consumption, as well as cut risk of abnormal wear between friction pair. To ensure the normal working condition of cylinder liner and piston ring as well as saving energy, it will be of great significance to find a suitable way to monitor the lubrication condition between cylinder liner and piston ring.In this paper, the author chose the specimen of cylinder liner and piston ring as friction pair to research AE phenomenon between them at different test conditions by using a reciprocating type tribotester. In combination with conventional lubrication evaluation parameters such as, friction force, frictional coefficient, friction power and contact temperature, the effects of normal load, relative sliding speed, oil type(viscosity) as well as surface roughness on AE parameters are investigated. Some analyses for AE signal in frictional process are also deployed by methods of distribution analysis, correlation analysis, short-time Fourier transform and wavelet transform.The results show that, AE characteristic parameters are sensitive to the effect of test condition on lubrication condition. Generally, the AE parameters increase as the normal load, relative sliding speed, surface roughness increase, but decrease at lower oil viscosity. During reciprocating sliding process, the AE parameters RMS, ASL, energy are minimized at TDC and BDC, then maximized near the TDC and BDC. At the low load test condition, there is a tendency in declination for RMS, ASL, energy at crank angle of 90°and 270°, however this regularity becomes ambiguous as load increases. By comparison, AE parameters energy, RMS, signal strength and absolute energy can be chosen as the first preferences to evaluate lubrication condition between cylinder liner and piston ring.