Experimental Studies On Friction Magnetic Memory Effect Of Ferromagnetic Workpieces Under Different Geomagnetic Field And Residual Magnetic Field Condition

In the friction process,the formation and change of magnetic memory signal on the ferromagnetic wokpiece surface are influenced by many factors.Hence,it is significant to carry out friction magnetic memory test in which different influence factors are researched.And the physical nature of friction magnetization of ferromagnetic materials and the mechanism of magnetic memory effect are revealed in friction process.The test not only enriches the theory of magnetic memory testing technology,but also provides a new method of wear condition monitoring.Therefore,the following researches are carried out in this thesis:(1)In order to investigate the influence of geomagnetic field and residual magnetic field on friction magnetic memory effect,the test method of friction magnetic memory effect is proposed which is based on the vertical magnetic shield friction test system.Furthermore,the specific test scheme for each influence factor is present in the test method.(2)The friction test was carried out by using the friction pairs of the 316 L pin and the 40 CrMo block.And the variation features of magnetic memory signal were analyzed in different friction stages.Combined with the theory of ferromagnetics and metal wear,the mechanism of magnetic memory effect was systematically expounded.(3)Based on the vertical magnetic shield friction test system,the influence of geomagnetic field and residual magnetic field on friction magnetic memory effect were studied.It was indicated that the increment of friction magnetic memory signal of the specimen surface was increased with the intensity of geomagnetic field when the direction of the specimen was changed which made the specimen under different intensity geomagnetic field;Friction magnetic memory signal of the demagnetization specimen was very weak under the condition of geomagnetic shielding,but friction magnetic memory signal of the high remanence specimens was increased with the intensity of residual magnetic field.It illustrated that residual magnetic field in the specimens could also stimulate magnetic memory effect.(4)The characteristics of magnetic memory signal on the 40 CrMo specimens surface over time were analyzed by test.The results shown that friction magnetic memory signal was declined with the natural aging time and tended to be a constant which was higher than the initial value.And the characteristics of magnetic memory signal curve still remained.Moreover,the higher the magnetic field intensity on the specimen surface was,the more significantly magnetic memory signal declined with the aging process.(5)The average of friction magnetic memory signal increment was chosen as the characteristic parameter and the relation between the characteristic parameter and wear condition was studied by the friction test.It was shown that the average of magnetic memory signal increment was increased linearly with the wear scar area under the same surface pressure;According to the trend of magnetic memory characteristic parameter curve,the macro morphology and wear mechanism could be qualitatively reflected to some extent,which would provide the basis for the application of magnetic memory testing technology in wear condition monitoring.