Research On The Stress And Characteristic Parameters Of Ferromagnetic Material Based On Electromagnetic Ultrasound

Ferromagnetic materials are widely used in the fields of transportation,energy,chemical engineering and large machinery because of its excellent mechanical properties.However,due to the internal stress concentration and organizational defects,as well as environmental corrosion and load fatigue objective reasons,there are security risks in the practical application.Therefore,the non-destructive testing to stress state and microscopic characteristics of the ferromagnetic material has become an important issue.This article mainly uses the magnetostrictive mechanism of the EMAT to test the internal stress and microscopic properties of the material.The main research work of this paper includes:(1)The article first introduces the basic electric,magnetic,acoustic theory and the principles of electromagnetic ultrasound.The EMAT transduction mechanism based on the Lorentz force mechanism are also analyzed.In particular,it detaily introduces the stress and material property parameters detection based on magnetostrictive mechanism of the EMAT.(2)The EMAT transducer is optimized and simulated by COMSOL Multiphysics multi-field simulation software in order to design the best transducer for the experiment of this system.Then,a stable and reliable electromagnetic ultrasonic hardware circuit system is set up,including high-power pulse excitation circuit,preamplifier circuit,impedance matching circuit and time-averaged data acquisition module.(3)A cantilever beam experiment device is designed to measure the strain in materials.The article draws the magnetic flux density-ultrasonic signal amplitude curve under different stress.The first valley point and the first peak point in the curve are extracted to analyze the influence of compressive stress.(4)Under the condition of magnetostrictive mechanism,the effect of different material hardness on the magnetic flux density-ultrasonic signal amplitude curve is studied.It is found that the smaller the hardness of the material,the larger the amplitude of the ultrasonic signal.