Study On Tribological Design Of Cylinder-ring Running-in Process

Internal combustion engine is an important energy conversion system in industrial production and daily life.Improving the service life and working efficiency of internal combustion engine is the key work of vehicle engineering research.From the perspective of tribology,cylinder-ring is the key friction pair in internal combustion engine.The running-in design of cylinder-ring is of great significance to improve the service life of internal combustion engine and reduce friction loss.In order to study the optimization of running-in condition parameters in the running-in design of cylinder-ring,firstly,a comprehensive test of general working conditions in the running-in period is designed for the selected cylinder-ring of diesel engine.The test method is sample test,collecting friction signal,friction vibration signal and cylinder liner surface morphology data before and after running-in.Then,the friction signal and friction vibration signal in the reciprocating friction movement of cylinder-ring are smoothed and wavelet denoised respectively.The signal processing results show that the mean smoothing method can effectively transform the reciprocating friction signal into a time series signal with continuous size change;Test results there are three typical friction signal evolution processes in the surface cylinder liner piston ring running-in test: the first friction signal increases gently and then decreases and gradually tends to be stable,the amplitude of friction vibration signal also increases and then decreases with the running-in process and gradually tends to be stable,and the second friction signal mutation caused by wear particles exists in the running-in process,The third is the combination of the first two evolution laws.Secondly,in order to study the chaotic characteristics of friction signal time series in the running-in process of cylinder-ring,the basic theory of chaotic attractor and the calculation method of characteristic parameters are introduced.The results show that the time series of friction signal and friction vibration signal in cylinder-ring running-in test meet the basic characteristics of chaotic signal,with continuous broadband power spectrum,positive maximum Lyapunov exponent and finite positive Kolmogrov entropy,Therefore,chaos theory and characterization parameters can be used to analyze it.Then,the concept and characterization parameters of running-in attractor are introduced,the phase space of friction signal and friction vibration signal obtained in the test are reconstructed,the running-in attractor is drawn,and the correlation dimension,Lyapunov exponent and Kolmogrov entropy of running-in attractors with similar shape and size are calculated,The results show that the shape and size difference of running-in attractor can qualitatively identify the wear state of cylinder-ring,and the characterization parameters of running-in attractor can quantitatively distinguish similar running-in attractors.Further,in order to study the evolution law of running-in attractor in the running-in process of cylinder-ring,the chaotic characteristics of the collected friction signal are analyzed,and the signal evolution law,phase trajectory evolution law and chaotic characteristic parameter evolution law of friction signal and friction vibration signal are studied respectively,The results show that the three typical running-in processes have common evolution laws: with the running-in process,the volume of the running-in attractor gradually decreases,the shape becomes rounded and remains stable,and the correlation dimension of the friction signal and Kolmogrov entropy gradually increase and remain stable;When the signal mutation occurs,the running-in attractor volume increases,the shape is irregular,and the correlation dimension and Kolmogrov entropy decrease;The evolution process of chaotic characteristics of friction signal and friction vibration signal is consistent.Finally,in order to optimize the speed and load parameters of cylinder-ring running-in process,the running-in time under different working conditions is determined combined with the evolution law of signal itself and running-in attractor;The evaluation indexes of running-in quality under different working conditions are given by combining the fractal parameters of surface morphology,the amplitude of friction vibration and the correlation dimension of running-in attractor;The working condition parameters of cylinder-ring running-in process are optimized by multi-objective.The results show that in the running-in process of cylinder-ring,the working condition parameters of running-in period can be designed according to the optimal solution set obtained by multi-objective optimization,so as to shorten the running-in time and improve the normal working stability.