Study On Lubrication Condition Between Cylinder Liner And Piston Ring Based On Acoustic Emission Technology

As a new dynamic non-destructive testing method, Acoustic emission technology can effectively check out crack propagation, elastic-plastic deformation and instantaneous elastic waves emitted by other forms of damage, which can be used in the fault forecast of materials, so it has a bright future in real-time detection of fault diagnosis. And the tribological characteristics between piston rings and cylinder liner play a very important role to the engine’s performance and life. Good lubrication not only can reduce the friction and energy consumption between the cylinder liner and piston ring, but also can effectively avoid the abnormal wearness. However, lubrication is a dynamic process that occurs between two friction surfaces, which can not be directly measured online.So it is of great significance to bring Acoustic Emission Technology into the dynamic monitoring of lubrication between the cylinder liner and piston ring. The main purpose of this thesis is to research the wearing condition between cylinder liner and piston ring in one cycle by using Acoustic Emission Technology and establish the relationship between acoustic emission signals and lubrication.This study brings in crank sensor to research the signal variation characteristics in one working cycle under different conditions based on a reciprocating testing machine of cylinder liner-piston ring. And the collected acoustic emission signal can be effectively de-noised and extracted by using the Fourier transform and so on. And by changing the load and relative velocity between the cylinder liner and piston ring, we can analyze the relationship between the characteristic parameters of acoustic emission signals with loads and speeds, and establish the relationship between the acoustic emission signals and liner lubrication state. Finally, to analyze and judge faults through broken oil experiment.The results show that the acoustic emission signal of one cycle changes like’M’ under different loads and speeds, and the minimum value is at the Top Dead Center and the Bottom Dead Center of the reciprocating tester, and the maximum value is near the midpoint of the stroke. Under the experimental conditions, the cylinder-piston ring is in boundary lubrication. Through oil off tests, the Acoustic Emission signal violently increased when scuffing. Moreover, this paper shows that under the experimental conditions, most of the acoustic emission signal comes from the elastic-plastic deformation, crack formation and propagation. The conclusion of this study indicate that RMS and absolute energy can be a good reflection of the lubrication state between the cylinder liner and piston ring.