Study On Life Reliability Of A Diesel Engine Power Units

Internal combustion engine as a kind of traditional power machinery is developing towards the direction of high power and high compression ratio in order to meet the relevant emission regulations.For a whole vehicle,the engine is the most core part of its normal work.For an engine,the reliability of the power unit directly determines whether an engine can play the best performance.Therefore,it is necessary to conduct more in-depth research on the reliability of the engine power unit to ensure that the engine has good working performance to meet the increasing working requirements.Diesel engine power unit is composed of piston group,connecting rod group and crankshaft group.The small end of diesel engine connecting rod is connected with piston through piston pin,and the big end of connecting rod is connected with crankshaft.During the actual working process,it receives the gas pressure from piston and pushes crankshaft to rotate at the same time.Therefore,the normal working of connecting rod is the primary premise of crankshaft's external work.In this paper,the connecting rod with complex working environment is selected as the research object.The main work is as follows:(1)Firstly,the mechanical analysis of power unit during the working process is carried out,which is the basis for the verification of the subsequent multi-body dynamics calculation results.(2)Based on the multi-body dynamics software ADAMS,the model of diesel engine power unit is established,the load time history of connecting rod working cycle is extracted,and compared with the theoretical calculation value to verify the reliability of the calculation result of multi-body dynamics software.(3)ANSYS is used to calculate the stress-strain field in the structure when the connecting rod is in the worst condition,and its safety is evaluated based on the traditional strength theory.(4)Based on the fact that connecting rod will be subject to alternating load during the actual working process,so the paper firstly predicts the fatigue life of the connecting rod without initial defects based on the nominal stress method of S-N curve,and evaluates whether it meets the requirements of the actual working cycle.(5)During the process of production or use,it is very likely to introduce some defects into the structure,the most serious one of which is the crack.Based on this fact,this paper first explores the influence of the existence of the crack on the static strength of the structure,and then explores the propagation life of the crack when connecting rod is affected by the disturbance load.At last,the reliability of this type of connecting rod is evaluated comprehensively.