Research On The Surface Morphology Of Connecting Rod Bushing’s Influence On Interference Fit

With the development of engine towards high-speed, high-power and high-compactness,problems on its parts’ structural Strength and reliability. The important influencing factors arematerial selection, machining, fit selection etc. Engine’s connecting rod bushing, connectingparts between piston and connecting rod is the key part of engine and its performancesdirectly affects performances of engine’s reliability and life. The tin-bronze bushing which hasbeen developed through power spinning, has excellent performances such as high strengthhigh hardness abrasion resisting long life, especially excellent comprehensive mechanicalproperties. On the high specific pressure condition, the kind of bushing satisfys the needs ofhigh speed high-power diesel engine’s correlated service performance.But up to now,researches about surface morphology influence on fit performance between bushing andconnecting rod’small end are inadequate, restricting the performance of the kind of bushing.Based on the theory of fractal interpolation, this paper reconstructs the surfacemorphology of connecting rod bushing, compiles program with the APLD parametriclanguage, creates the connecting rod bushing’s three-dimension solid model with the surfacemorphology characteristic, carries out the contact analysis, deeply studying surfacemorphology effects for interference fit.In the paper, the achievements of former researcher in connecting rod bushing arereviewed and analysised for the first time, which make the research contents and the keyproblems clearer. In order to search a method for solving the problem, comparative analysis ofthe traditional elastic-plastic theory about interference fit are carried out, indicating presentcorrelated technology’s advantages and disadvantages. The surface morphology of connectingrod bushing is described and constructed and the model of surface morphology is created.Getting the initial data is the key step of construction. This paper gets the initial data through two methods: mathematical simulation and experimental measurement. Based on the data andfractal interpolation theory, compiles program, get various surface morphology and comparethe surface morphology through experimental measurement to the electronic photos. Theanalysis results indicate that these models are reasonably precise, so they could be the basicmodels for the following researches. On this basis, the paper select the appropriateinterference fit model, the appropriate solid model of surface morphology and contact model,and apply orthogonality analysis method to determine key parameters: element size andnormal contact stiffness. In the end, as to connecting rod bushing model owning differentmagnitude of interference and different surface morphology, the finite element analysis iscarried out, obtaining the distribution of contact stress, contact gap distance etc. It isconcluded that improving the surface morphology’s smoothness to some extent, is helpful toimprove uneven distribution of stress and reduce surface morphology’s influence onmagnitude of interference, ultimately improving fitting property and cooperating parts’ life.