Research On Dynamic Analysis And Fatigue Calculation For Crank-link Mechanism On Low Speed Diesel Engine

Low speed diesel engines have large and complex structure.As for marine diesel engine,it works under a condition that varies rapidly,which makes the the strength and reliability of main parts on marine diesel engine should be high enough,so designer should analyze the performance of main parts under different conditions to make sure the diesel works safely and steadily.In this thesis,many analyze tools were used to analyze the dynamic stress of the crankshaft and connecting rods of a marine low speed diesel engine.Stress distribution and change of the crankshaft and connecting rods was calculated and strength was checked when the diesel was working steadily.Then,the differences of two analyze methods were compared,and the results and computing methods were analyzed.At last,fatigue calculation software was used to calculate fatigue safety factor of the crankshaft and connecting rods,and reliability of these two key parts on diesel was checked.In this thesis,the research work mainly focused on these aspects:Firstly,the analyze model of low speed diesel engine crank-link mechanism was established with Pro/E,and then it was imported into ADAMS to establish rigid body dynamics model.Major simulation parameters were set and analysis was conducted.According to the results,force condition of main parts was analyzed.Secondly,Hypermesh was used to mesh the crankshaft and connecting rods,and these parts were calculated in Optistruct to get the mnf file.Flexible body model was built and the simulation was conducted again to get the stress change condition of the crankshaft and connecting rods when the diesel is working.Then the strength was checked and calculation results were compared with the rigid body model.Thirdly,Ansys-Workbench was used to establish the dynamic simulation model of crank-link mechanism and stress distribution was obtained.Then,the results from ANSYS and ADAMS were compared and the differences between two computing methods were analyzed.Last,Msc.Fatigue was used to analyze the fatigue performance of the crankshaft and connecting rods,and the safety factor contour during working process was obtained.The reliability of crankshaft and connecting rods was verified.As a conclusion,we find that the crankshaft and connecting rods are working in a safe condition.