Research About Dynamic Response On Connecting Rod Of Diesel Engine Based On Finite Element Analysis

The connecting rod is an important part of the crank-link mechanism.On account of thework of gas pressure,inertial forces,bolt preload, liner bushing and step brass interferencepower,its sress and deformation changes cyclically,prone to fatigue failure. For the structureoptimization and life improvement, the composite structure model of connecting rod has beenestablished,including connecting rod body,connecting rod cap, connecting rod bolt,connecting rod liner bushing，connecting rod step brass，piston pin,crank pin and so on.On thebasis of contact and blink state dynamics theory,using finite element method,under finecontact set conditions,the analysis method in the static and dynamic force for compositestructure model of connecting rod has been studied,provides reference for connecting rodstructure design and optimization.Based on the actual structure and size of a type of diesel engine,using three-dimensionalmodeling software Pro-e4.0 to establish a solid model for connecting rod,includingconnecting rod body,connecting rod cap, connecting rod bolt, connecting rod liner bushing，connecting rod step brass，piston pin and crank pin,then fit them together;due to the symmetryof the structure and stress,in order to reduce the amount of calculation,half of the model istaken and imported to ansys12.0 for finite element analysis,when the model is discreted,thecalculation precision and speed is taken into account, then the appropriate grid size isdecided.Based on the finite element model of composite structures,direct load method andtemperature equivalent method is used to impose preload,the impact for the distribution ofstress and deformation by different load imposed method is studied;the distribution of stressand deformation for the contact surface under the condition of the maximum tensile and themaximum pressure is studied. The software AVL-BOOST and woschniAnisits combustion model is used to establishthe numerical analysis model, the simulation analysis of diesel engine work process is done;the calibration value of single cylinder power,largest outbreak pressure,fuel consumption rateand mean effective pressure is used as evaluation to verify and correct the model, then thenecessary load boundary conditions for dynamic response analysis is provided .On the basis of combined structure model of connecting rod,the displacement of crankpin is constrained and the symmetry constraint is imposed on the subdivision surfaces of theother parts,meanwhile the assembly relationship between parts is taken into account, betweenconnecting rod body and connecting rod cap，piston pin and connecting rod linerbushing,connecting rod body and connecting rod step brass,connecting rod body andconnecting rod bolt,11 contact is set;on the basis of the cylinder pressure curve obtained bysimulation,load step is set,time history load is applied on the piston pin,then the combinedmodel for contact-dynamic response analysis is established;under the conditions of finecontact settings and dynamic load,the distribution of stress and deformation is studied,theresults is compared with static analysis,the reliability of dynamic response model andboundary conditions is verified well,and all of this provide support for the establishment ofloading spectrum for fatigue life prediction.