Research On Multifunctional Nondestructive Testing Sensor Based On Magnetic Method

Steel and other ferromagnetic materials are widely used in mechanical and electrical,metallurgical and mineral resources,petrochemical,water conservancy and hydropower,transportation and many other industries,has most application in the world.Precision and heavy machinery ever more with the development of industry and technology,but most devices are working in high speed,high temperature,high pressure and other severe environment,various damage will appear in the long run,in turn resulting in equipment failure,even catastrophic consequences.Therefore,it is very important to detect and evaluate the damage of ferromagnetic materials accurately,quickly and efficiently.Nondestructive testing technology is an important means to ensure the safe operation of equipment,which have many varieties and different technical features and application scope.Magnetic nondestructive testing technology for the detection of ferromagnetic materials have congenital advantages,which applies more and more extensively.Based on the theory and application of magnetic memory detection,magnetic flux leakage detection and Barkhausen noise detection,this paper puts forward the research ideas of multifunctional nondestructive testing sensor based on magnetic method,and has carried out a lot of research work.According to the mechanism and characteristics of the three kinds of magnetic detection methods,a multifunctional detection sensor is developed,which includes signal receiving,moving magnetization,excitation signals generation and control and other parts.The signal receiving part is composed of 7 groups of signal receiving units,each unit can measure two signals in X direction and Z direction.The movable magnetizing part is mainly composed of 6 excitation coils,and the rotating magnetic field can be formed in the material under test.The excitation signals generation and control part use DDS technology to synthesize excited signal of sine wave with Variable frequency and phase.The specimen of 45 steel were fabricated,which has residual stress bands and 7 cracks with different angles.Determining the experimental parameters and signal processing methods,building test system and designing experiment.Then using three methods in turn to detect,and processing received signals.The results show that the magnetic memory scanning test can identify the existence of stress and crack,enhanced magnetic memory detection improves the sensitivity and the stability,magnetic flux leakage testing can identify the crack at any angle,barkhausen noise detection can make a preliminary quantitative evaluation of stress.The stress and crack damage state of the specimen can be good evaluated with the use of the three methods.