Research On The Deformation Of Bearing Bore In The Secondary Assembly Process Of Diesel Engine

Industry is the foundation of the national economy.The engine is the core of many mechanical equipment.Engines are widely used in engineering production.The manufacturing level of engine is one of the signs of the national industrial level.Industrial production has continuously improved requirements for engine performance and the requirements of engine manufacturing technology,especially the higher requirements for the machining accuracy of bearing bores.The bearing bore of a diesel engine is one of the locating bases during assembly and processing process.Its machining accuracy has a great influence on the working performance of the crankshaft.The bearing bore is generally assembled and processed after pre-tightening bolts.The crankcase and the cylinder block are assembled with bolts before machining the bearing bore.After processing the bolts and reassembling them,the bearing bore deforms and the interface misaligns.It will lead to stress concentration at the contact area between the bearing bore and bearing bush,which is prone to bearing contact fatigue failure.In order to analyze the structural reason and reduce the deformation of bearing bore,the finite element simulation model of the bearing bore during secondary assembly process is established.The deformation characteristics of the bearing bore during the secondary assembly process are calculated.Quantitative analysis of the deformation characteristics of the split bearing bore is carried out,and a new method for evaluating the amount of the misalignment of interface is proposed.The correctness of the modeling process and the validity of the simulation results are verified through experiments.The influence of preload torque,friction coefficient,and unilateral positioning pin constraint on the misalignment deformation of the bearing bore is studied.The theoretical analysis of loading conditions and dynamic process of actual deformation is presented.This paper reveals the elastic-plastic deformation mechanism of the bearing bore during secondary assembly.According to the technological reason,the process test and structural mechanics test are carried out.The three coordinate values of the circumferential nodes are measured,and the deformation of the bearing bore and the misalignment of the interface are calculated.The test and analysis of structural mechanic are carried out,and the strain values on both sides of interface during the bolt pre-tightening process are measured.Based on fractal theory,the tribological analysis of crankcase interface is carried out.The surface roughness and character parameter of the milled surface are measured.The structure function method is used to calculate the fractal dimension and characteristic scale factor,revealing the fractal characteristics of the surface topography of the interface.Substituting the calculated fractal parameters into the contact analysis and calculation model of spherical asperities.Control the characteristic scale factor to increase the profile amplitude to remodel the interface.The influence of the friction coefficient of the interface on the amount of deformation is presented.The structural and technological reasons for the misalignment and deformation of bearing bore are comprehensively analyzed,and the technological improvement plan and structural improvement plan are presented.The process and pre-tightening conditions for the secondary assembly of actual production are obtained to solve the problem of large deformation of the bearing bore during the secondary assembly process.Compared with the original process,the deformation of bearing bore is improved by 31.90% on average.The improvement scheme has been verified and accepted by the enterprise,and the application certificate is issued by the enterprise.