Research On Stress-magnetism Coupling Of X70 Steel Based On Non-contact Magnetic Tomography Method Inspection

In recent years,with the completion of China's northwest energy channel,the opening of the northeastern energy channel,and the opening of the southwestern energy channel,the construction of major national lifelines has significantly increased the operating mileage of buried steel oil and gas pipelines.Because oil and natural gas are flammable,explosive,and prone to static electricity,it is crucial to ensure that steel pipelines in service are in good condition.It is particularly important to monitor and inspect the pipeline operation in the latter stage under the premise of ensuring the quality of the pipeline.At present,the more convenient detection is non-excavation non-destructive testing.This paper mainly studies the stress and magnetic field coupling mechanism of high-strength pipeline steel X70 steel in order to provide theoretical support for X70 steel in magnetic detection.By understanding the magnetic and magnetization curves of materials,hysteresis loops,dislocation movements,pinning,and movement of domain walls,the stressmagnetic field coupling relationship during the elastic deformation phase is modeled according to the principles of system energy balance and magneto-mechanical effects.and elastic deformation stage J-A consideration of plastic deformation on the basis of the model stage irreversible magnetization,magnetization hysteresis,can be pinned,the equivalent magnetic field strength in the ideal conditions,equivalent to the actual field strength and the elastic deformation stage with similar The magnetoplastic properties of the energy generated to counteract the movement of the domain wall establishes a magnetic-magnetic coupling relationship during the plastic deformation stage.Based on the establishment of the relationship model between relative magnetic permeability and detection signal,a relative magnetic permeability measurement experiment platform was built.This platform can measure the magnetic hysteresis loop of X70 steel under different excitation signals and different frequencies,and can obtain the best magnetic Hysteresis loops,and stress and relative permeability can be obtained by measuring tensile specimens.Using COMSOL Multiphysics software simulation of the static,static magnetic coupling force and the magnetic simulation of stress in the static magnetic field simulation,and simulation by changing the types of parameters.The X70 steel plate specimen was measured offline at different tensile forces under the conditions of demagnetization and non-demagnetization,and the internal magnetic field strength was measured at the elasto-plastic deformation stage.Based on the above studies,a force-magnetic coupling model was established during the elasto-plastic deformation stage.The relative permeability of X70 steel was measured,and the relationship between stress and relative permeability was proposed.The mutual verification was performed through finite element simulation and elastoplastic deformation stage tensile test.