Running-in Design Method Of Main Bearing On Marine Low-speed Diesel Engine Based On Light Curing Composite Lubrication Structure

The main bearing of marine low-speed diesel engines is often in a mixed lubrication state under low speed and heavy load,and the oil film thickness is low.It leads to poor running-in,which shortens the service life and reduces the service reliability of the main bearing.To improve the running-in quality and efficiency of the main bearing,the fractal parameters are used to evaluate the running-in quality,and the composite lubrication structure was the main measure.The effects of zinc borate and its mixed oil additive with silicon dioxide on the running-in of the main bearing were studied,respectively.Then,the construction method of a composite lubrication structure filled with mixed solid lubricant was studied.Furthermore,the multiple synergistic running-in mechanisms of solid lubricant and texture were clarified.Finally,the optimization design of the composite lubrication structure and running-in condition was realized.The main research contents are as follows :The effect of zinc borate oil additive on the running-in quality of the main bearing was studied.The nonlinear characteristics of wear surface topography were characterized by fractal dimension and multifractal parameters.The nonlinear characteristics of the friction coefficient were characterized by phase trajectory and correlation dimension.Then,they used to evaluate the running-in quality of the main bearing.The results show that the fractal dimension increases to 1.48 after adding the zinc borate additive.The correlation dimension is stable at around 1.7.The spectral and spectra difference of multifractal parameters is reduced to 0.47 and 1.0,respectively.The convergence degree of phase trajectory increases.This shows that the running-in quality of the main bearing has been significantly improved.However,the zinc borate additive weakens the interaction of the asperities on the contact surface and reduces the running-in efficiency of the main bearing.To improve the running-in quality and efficiency of the main bearing,zinc borate and silicon dioxide were used as mixed oil additives.The running-in quality and efficiency of the main bearing were evaluated by the multifractal parameters of the surface topography and the correlation dimension of the friction coefficient.The results show that compared with the single zinc borate or silicon dioxide additive,the correlation dimension of the mixed additive is increased by 18.2 % and 19.1 %,the multifractal parameters are reduced by 43.0 % and 32.4 %,and the running-in time is reduced by 25.0 % and 40.0 %,respectively.It shows that the mixed additive can improve the running-in quality and efficiency of the main bearing.Its excellent tribological properties are attributed to the boundary protective film formed by zinc borate and the rolling,self-healing,and polishing effects of silicon dioxide.However,the solid lubricant is dispersed in the oil,the local concentration is low,and it is difficult to maintain on the surface of the main bearing for a long time.To realize the storage,release,and film formation of solid lubricants between friction interfaces,the light curing construction method of solid lubricant-texture composite lubrication structure was studied.Mixed additives and photosensitive liquid resin were used as solid filling materials.The composite lubrication structure was constructed by the light curing method.The results show that the composite lubrication structure constructed by light curing has achieved excellent friction-reducing and anti-wear performance.It can effectively improve the running-in quality of the main bearing.There are multiple synergistic effects between the mixed solid lubricant and the texture.The micro-rolling of silicon dioxide promotes the spreading of zinc borate.The boundary protective film formed by zinc borate is beneficial to the retention of silicon dioxide.Texture can affect the release rate of solid lubricant.Scientific design of composite lubrication structure and running-in condition is very important to improve running-in efficiency and quality.Based on the experimental data,the fractal prediction models were established.The prediction accuracy can exceed 80 %.With high running-in stability,high surface quality,and short running-in time as the optimization objectives,a multi-objective optimization design was carried out to obtain the optimal solution set and the optimal running-in parameter set.The verification test is carried out,and the results show that the error of the optimal solution is controlled within 10 %,and the accuracy is high.According to the optimization goal,the appropriate texture diameter,texture area ratio,speed,and load are selected,which is beneficial to the running-in quality and efficiency of the main bearing.The calculated optimal solution set provides a reference for the practical application of composite lubrication structure.