Dynamics Simulation Of Torsional Vibration Of Crankshaft Of Diesel Engine And Fatigue Analysis

With the development of automobile industry, car has not just as people travel tools. Car has been integrated into our daily life, nowadays people put forward higher requirements on the car the indicators. Cars’ noise, vibration, and harshness(NVH) are the important measures of automobile comfort index. Engine’s NVH as one of the important factors affecting the vibration of the vehicle, has been drawn more and more attention of the manufacturer. As an important component of the engine crankshaft, its cost often account for a third of the total engine. The crankshaft’s good or bad performance will directly influence the performance of the whole machine. Diesel engine crankshaft’s torsional vibration characteristics, as well as the research of fatigue reliability has important significance for NVH of engine.This paper is based on the 4100 diesel engine as the research object. Using the finite element software ANSYS, the multi-body dynamics software ADAMS and DesignLife fatigue life analysis software, the static strength test, dynamic simulation and fatigue life analysis are taken on the crankshaft and connecting rod mechanism. The main works are the following:1) 3D model of crankshaft and connecting rod mechanism are built and assembled in UG software, the basic parameters of crankshaft, connecting rod, piston and others are got and the corresponding mechanical analysis is established. This provides the basis for subsequent theoretical analysis.2) Multi-rigid-body dynamics simulation was carried out on the crankshaft connecting rod mechanism. The various parts’ kinematics relationship are got under the typical working conditions.3) Using the flexible crankshaft take the rigid crankshaft and harmonic response analysis are taken on the crankshaft system to test the reply of torsional vibration. The purpose is to study the influence on the crankshaft torsional vibration amplitude under the different rotational speed and the different the load. Results show that with the increase of engine speed and load, the torsional vibration of crankshaft are tend to be larger, and speed greater influence on torsional amplitude values. Meanwhile, the main journal, connecting rod journal load spectrum results is got. These load spectrum provide important load boundary conditions for further study of fatigue life of the crankshaft.4) Using the ANSYS generate the finite element of the crankshaft. The natural frequency and vibration mode is got from the free modal analysis results. The limit load is got based on multi-body dynamics simulation and the static strength check is taken. The results shows that the static strength of crankshaft is over its use standard and it can meet the requirements. It can provide the basis for subsequent analysis of the fatigue life.5) Finally, the crankshaft fatigue life prediction is taken combining with load spectrum that was got from multi-body dynamics analysis and the stress and strain analysis results of the crankshaft under various conditions. The fatigue life analysis results show that crankshaft’s the most dangerous part of the frequency is above 1310 times.