Engine Crankshaft Magnetic Memory Testing And Fatigue Life Assessment Study

According to Ministry of Public Security statistics, at the end of2013, theownership of national car was127million, compared with the end of last year, it hasan increase of8.32million and8.02percent. Motor vehicle population occupied48.87%of the total, which increased1.81percent by the end of last year. Huge car ownershipalso means that the peak of the automotive replacement market is also coming, scrapcar recycling, dismantling, remanufacturing and other issues in the automotiveindustry and the development of recycling economy will become more important.American and Europeans remanufactured products occupy a large market sharein re-manufacturing industry, which is still emerging in China. Remanufacturingtechnical requirements of the crankshaft main includes nondestructive testing andevaluation of life which has guiding significance of remanufacturing automotiveindustry, the focus of this article is also non-destructive testing. Using the method ofmagnetic memory nondestructive testing for a12V diesel engine crankshaft, weestablished a completed set of non-destructive testing program and life evaluationalgorithm, the test results are combined with the life assessment, thus effectivelyreducing the fatigue life assessment error, which improves the life of evaluationresults, the evaluation of the feasibility of re-manufactured products, and provides aneffective theoretical support.This paper begins with the basic theory of fatigue damage accumulation model toproceed with various ideas on the force of the crankshaft features a detailed analysis,and use the finite element software to analysis the stress and strain of the crankshaft.Combined with the cumulative fatigue damage theory of crankshaft fatigue analysis,we established a model for the calculation of the fatigue life of the crankshaft. Theresults show there is a significant stress concentration in the spindle neck fillets andconnecting rod journal fillets of the crankshaft, we get the maximum stress value ofthe crankshaft and the maximum strain value, and the amount of damage and the lifeof the crank shaft.In order to accurately reflect the failure of the process and its life assessment, weexplored the variation of magnetic memory signal and launched a metal fatigue crackgrowth tests of35CrMoA. During the experiment, the curve of wears component ofthe magnetic field strength values Hp(y) shows dramatic changes in the stress concentration area, and the gradient of magnetic field strength K appears extremevalue at the same time. They present different laws with the increase of loading times,and Kavgaccording to the different stages in the components has a corresponding trend.The experiment explores the metal magnetic memory testing methods for crankshaftlife assessment. By studying the coupling mechanism of magnetic and force, wefurther explore the physical principles and mechanisms of the metal magneticmemory testing methods, and make use of relevant principles including therelationship between stress and permeability to creating a mathematical model formagnetic characterization of stress concentration area. And we find the numericalrelationship between stress and magnetic memory signals, we has formed a completemethod for remanufacturing crank magnetic memory testing and life assessment.By analyzing the metal magnetic memory testing data of scrapped crankshaftsand remanufactured crankshafts, we have verified the feasibility of the crankshaftremanufacturing.