Analysis Of Vibration Characteristics Of Marine Diesel Engine Crankshaft Based On Multi Body Dynamics

The diesel engine is the most important power output device, of which the crank shaft is one of the most complex and easily damaged parts. The optimization of the crankshaft design has been the first task of diesel engine noise and vibration reduction.The research object of this thesis is a four-stroke four-cylinder diesel engine, based on the finite element theory and multi-body dynamics theory, CAD and CAE software, by the finite element post-processing after general processing principle, the modeling and simulation of diesel engine crankshaft, it calculates the natural frequency, vibration mode of the diesel engine crankshaft and the vibration characteristics and lubricating characteristics in one working cycle, the specific methods are as follows:The paper applies the three dimensional modeling software Solidworks, to establish three-dimensional model according to the detailed dimensions of the crankshaft, saving the oil hole and part of the chamfering. It meshes the crankshaft in Hypermesh, for the convenience of the subsequent reduction of crankshaft and bearing model, the spindle neck and crank pin adopts hexahedral grid cell division, the crank arm applies tetrahedral grid cell, and then the related properties like crankshaft materials and elastic model are set. In ABAQUS, free modal analysis is carried out on the crankshaft, acquiring the first 12 order natural frequency and vibration model. In AVL-Excite software, the diesel engine crankshaft multibody dynamics model is set, applying the correct boundary conditions, calculates the stress, displacement, velocity and acceleration of the crankshaft and main bearing during one working cycle of the crankshaft; and analyzes the parameters which can reflect the crankshaft lubrication, such as the smallest main bearing oil film thickness, the lard membrane stress and axis path, providing basis for the crankshaft design.Under the background of traditional design constraints and difficulty of simulating actual working condition, the thesis employs the research methods combining the finite element method and the multi-body dynamics method, which can carry on the analysis to the most stress-complex diesel engine parts, greatly improving the crankshaft precision in the design process, and provide certain guiding significance to the design and check for the crankshaft.