Research On Stress Detection Mechanism Of Metal Structure Based On Electromagnetic Characteristic Measurement

Military weapons are exposed in harsh and complex conditions in long term service process.Due to external load and environmental corrosion,bearing beams,engine blades,fixed joints and other force components are prone to suffer fatigue or even brittle fracture caused by stress concentration,which bring huge threats to national economy and personnel safety.Therefore,status detection of the equipment in service based on the stress measurement is of great significance in equipment safe service,effective maintenance,as well as quality assessment.Domestic stress detection starts relatively late,the most widely used at present is the X-ray detection method,which is mainly employed in stress detection beneath surfaces within 20 um.This method could hardly satisfy the status detection of equipment in service,due to the expensive testing equipment and high requirements of measurement conditions.Based on the eddy current testing,this paper mainly studies the influence of the stress on the electromagnetic properties of metal materials.The mathematical model of conductivity,permeability and stress is established through theoretical derivation and experiment,which lays the foundation for stress detection based on electromagnetic measurement.The main contents are as follows:The role of stress acting on the conductivity / permeability of metal component is studied.Conductivity and permeability of the metal are studied from the microscopic point of view.The mechanism and the magnetization process of the metal’s atomic distance,the internal defect morphology,the electronic structure and the energy band structure are analyzed,as well as the magnetic domain wall and other changes on the magnetic permeability of the mechanism.The feasibility of stress detection technology of metal materials based on electromagnetic characteristic measurement is demonstrated through theoretical analysis.The relation model between stress and conductivity of metal materials was established.Based on the piezoresistive effect,the metal force model of unit volume is discussed.The law of metal conductivity with stress change is qualitatively analyzed.The electrical anisotropy and three-dimensional stress direction of metal material are analyzed with extending plate stress distribution model.The mathematical model of stress and conductivity of metal members was established by theoretical derivation and empirical model,and the differences between the two models were compared.The stress-permeability theory of metallic materials is studied and the corresponding detection model is established.Through analyzing the action mechanism of stress on the structure of the magnetic domain,the stress detection model based on the permeability measurement is discussed in the view of energy.The relationship between the stress and permeability is deduced,and the measurement method of the transfer impedance and the electromagnetic properties of the material are confirmed.The measurement grid database of sensors is established with the COMSOL Multiphysics multi-physics finite element simulation software.The sensor calibration method is studied and the searching algorithm is used to realize inverse play of electromagnetic properties of the material.The experimental platform for stress-conductivity/ permeability measurement of metal materials is constructed.The non-ferromagnetic materials and ferromagnetic materials are tested and analyzed respectively.The changes of stress,conductivity and permeability are analyzed under uniaxial loading and cyclic loading.The data are analyzed with consideration of the measurement environment.The established mathematical model is validated and evaluated.