Characteristic Information Extractiontechnology Research Of Cylinder Liner-piston Ring Acoustic Emission

In the working process of the cylinder liner-piston ring,the main sources of acoustic emission signal come from the crystal elastic deformation,plastic deformation,shear,adhesive,generated by viscous friction between two contact surface micro convex body and fluid.Acoustic emission technology is a new dynamic nondestructive testing method,it can effectively detect transient elastic wave caused by damage in material such as crack extension,elastic-plastic deformation and other forms of damage,after that material status detection and defect prediction is completed,therefore,AE can be used to real-time,dynamic characterization of actual contact between the surface of cylinder liner and piston ring and lubrication condition.Main purposes of this article:To extract the excitation source produced by analysis the two-stroke diesel engine acoustic emission signals,and to study the acoustic emission signal caused by a reciprocating friction and wear testing machine.First of all,time-frequency analysis on top dead center and travel halfway point on the 5S35ME-B9 two stroke diesel engines is carried out by using the Fourier transform and Hilbert huang transform method,find the acoustic emission signals's excitation source in different time and frequency.Then friction and wear testing machine is set as the research object,find the relationship between the transformations of acoustic emission signal characteristic parameters along with the change of load and speed by changing the friction pair between the normal load and relative speed.In the end,set dry friction experiment to analysis the relationship between the acoustic emission signal and lubrication condition.Results show that,fuel injection,high temperature and high pressure gas combustion,the impact of the valve seat,contact between piston ring and honing grain on cylinder liner will produce obvious acoustic emission signal.According to analyze the different excitation source of acoustic emission signals,the working state of the different parts can be detected.Under different load and speed,the acoustic emission signal amplitude is change over time in one circle,and increased firstly and then decreased between TDC and BDC.the value of acoustic emission signal is minimum at top and bottom dead center of position,while between the two point is maximum.Under the same load,the acoustic emission signal amplitude and frequency increases along with the speed.When the speed is equal,the acoustic emission signal amplitude increases along with the load.When the load is too large,the acoustic emission signal will obviously increase,at this time,the friction pair lubrication becomes abnormal,and according to the acoustic emission wave,the location of the exception can be found.Under the same load and speed.Compare with sufficient lubrication,the acoustic emission signal amplitude in dry friction will have a significant increase.