| The diesel engine transmission shaft is an important part of the ship’s power plant,and its reliability and stability will directly affect the ship’s operation.At present,most of the research on torsional vibration of diesel engine shafting is based on linear theory,but it can no longer meet the development needs of modern shipbuilding industry.Although there are many researches on nonlinear components such as elastic coupling and gear,the research of the nonlinear characteristics on multi-degree-of-freedom system is still rare.This makes the research of this paper have important practical significance.In this paper,the diesel engine shafting of a ship is taken as the research object.Considering the nonlinearity of the elastic coupling stiffness and the internal excitation nonlinearity of the gear,the nonlinear motion differential equations of the torsional vibration of the diesel engine shaft system are established,and the system response is calculated according to the improved Newmark method.First,the lumped parameter method is used to simplify the model into a 20-degree-of-freedom system,and the moment of inertia,torsional stiffness,and diesel engine excitation are calculated.Secondly,based on the derivation of the nonlinear motion differential equations of the two rotor system,the non-linear motion differential equations of the diesel engine shafting system containing quadratic and cubic nonlinear terms are established.After considering the difficulty of solving the multi-degree-of-freedom system and the parameter vibration problem of the internal excitation of the gear,it is determined that the solution method of the nonlinear problem in this paper is the improved Newmark method,and the accuracy of the method is verified.Finally,the nonlinear response of the system under two nonlinear factors is calculated.It is found that the rigid nonlinear stiffness of the elastic coupling and the internal excitation of the gear will increase the system response.However,the soft nonlinear stiffness of the elastic coupling is more conducive to system vibration reduction.The greater the absolute value of the soft nonlinear stiffness,the better the vibration reduction effect.In this paper,the nonlinear differential equations of torsional vibration of complex shafting are derived,and a numerical solution method for the nonlinear torsional vibration response of diesel engine shafting is proposed.The effects of two nonlinear factors,the stiffness nonlinearity of elastic coupling and the internal excitation nonlinearity of gear,on the response of shafting are studied,which are meaningful in theory and engineering. |
