Metal Magnetic Memory And Ultrasonic Complex Method For Damage Degree Evaluation Of Used Ferromagnetic Component Before Remanufacturing

With the rapid society and population growth, the lack of land, energy and mineral resources will become more and more serious, therefore, it becomes more and more important for environmental protection, energy conservation and society sustained development. Remanufacturing engineering is a generic terms of all techniques and engineering activity to maintain and rebuild worn products, which takes the productive whole life as direction, takes the upgrade of the perfomance of worn products as goal, takes the good quality, high efficiency, energy saving, environment protecting as rule, and takes the advanced surface engineering techniques and industrializing process as measures. Remanufacturing engineering is fit for the development of society, which is widely recognized. Then, more and more issues come out from remanufacturing engineering. How to ensure product quality and upgrade the consumer confidence are the most important, related with the application of remanufacturing engineering.Taking nondestructive evaluation on residual life of remanufacturing core and quality ensurence of remanufacturing product as goal, and taking metal magnetic memory testing and ultrasonic testing as subject, in this research, the regularity of metal magnetic memory signals, which changed with loads, cycles and stress concentration, were studied, and the key parameter characterizing fatigue damage was found by static tension test and fatigue tensile test. Meanwhile, the fatigue life evaluating models characterized by metal magnetic memory signals and ultrasonic signals were gived, combined with fracture mechanics. In practical application, metal magnetic memory testing and ultrasonic testing were used to evaluate the worn crankshaft before remanufacturing, and nondestructive testing clamping fixture was designed. Some of main experimental results and conclusions are shown as follow.By static tension tests and fatigue tensile tests, the regularity of magnetic memory signals, changed with applied load, fatigue cycles and stress concentration factor, were investigated, and the key parameter between magnetic memory signals and fatigue damage was extracted. The influences of surface cracking, stress concentration, testing direction and lift-off height on magnetic memory signals were studied for the application of metal magnetic memory testing. The regularity of magnetic memory signals, influenced by friction wear, was studied. The results showed that magnetic memory signals were obviously affected by friction wear, and the key parameter between magnetic memory signals and friction wear was abnormal magnetic peak, which could quantitatively detect the size and site of friction area, and qualitatively estimate the degree of wear.The numerical models of magnetic memory signals, changed with applied load in static tension test and fatigue cycles in fatigue tensile test, were fitted based on test data. The simple models of fatigue life evaluation were constructed, which were characterized by magnetic memory signals and ultrasonic signals.Taking the worn crankshaft before remanufacturing as subject investigated, the simulation and failure analysis of crankshaft were done to confirm the stress distribution, risk area and failure reason. According to the results, metal magnetic memory testing was used to detect the surface cracking and stress concentration, and ultrasonic testing was used to detect the flaws in the crankshaft.Curved double angle beam probe was applied to detect the crankshaft because of the special construction of crankshaft. The calibrating method of probe was designed, and the testing procedure of worn crankshaft was confirmed. The special clamping fixture for ultrasonic testing on crankshaft was designed, and the problems of locating testing and quantitative testing were solved.Metal magnetic memory testing method of worn crankshaft before remanufacturing was confirmed for application. The key parameter KM, which was magnetic stress concentration factor, was extracted from the practical data, and used to estimate the degree of fatigue damage as three grades. The key value of KM for Stir engine crankshaft was confirmed in practical application. Finally, the quality of worn crankshaft before remanufacturing was estimated by metal magnetic memory testing and ultrasonic testing.