Research On Prediction Method Of Residual Life Of Crankshaft Based On Metal Magnetic Memory Theory

With the vigorous development of circular economy in China,remanufacturing projects aiming at high quality,high efficiency,energy saving and environmental protection are rising gradually.Marine diesel engine is a typical remanufactured product,and diesel engine crankshaft is the core component of diesel engine,so the remanufacturing of diesel engine crankshaft has guiding significance for the development of diesel engine remanufacturing industry.In order to show the value of crankshaft remanufacturing,the prediction of residual life of serving crankshaft becomes the most important link in the process of crankshaft remanufacturing.Therefore,this paper mainly studies the method of crankshaft residual life prediction,and proposes a new method of crankshaft residual life prediction based on metal magnetic memory theory.The main research contents are as follows:（1）Through the study of fatigue damage theory,it lays a theoretical foundation for fatigue analysis of crankshaft.Through the analysis of working conditions and common fatigue damage forms of marine diesel engine crankshaft,the relevant boundary conditions for finite element analysis of crankshaft are determined,that is,the magnitude of applied load and the mode of restraint.Thus,the fatigue damage parts of diesel engine crankshaft are determined accurately,and the detection cost of crankshaft is reduced.Through finite element analysis,the cycle number-concentrated stress curves under fatigue tension with different frequencies are obtained.（2）The basic physical principle of magnetomechanical effect is studied.Through the study of domain structure,magnetization and hysteresis phenomena,magnetostriction and crystal anisotropy,the causes of metal magnetic memory are analyzed from macroscopic and microscopic aspects.At the same time,a solid theoretical foundation is laid for the prediction of residual life of crankshaft by metal magnetic memory method.（3）The relationship between magnetic field and stress,the spatial distribution of magnetic field intensity and the distribution of magnetic field intensity of magnet are studied.A method to construct the expression of the relationship between leakage magnetic field intensity H and maximum stressσ_maxax at the stress concentration of ferromagnetic material is proposed.Combining with this expression,the possibility of knowing the stress value of ferromagnetic material only by measuring the magnetic signal on its surface is realized.（4）Combining with（1）and（3）,a method for predicting the residual life of diesel engine crankshaft is proposed,and a method for predicting the residual life of diesel engine crankshaft in a certain speed range is proposed by using weighted average method.The method is verified by simple ferromagnetic specimens,and its accuracy can reach 89%...