Research On Electromagnetic Detection System Of Residual Stress In Metal Components

Residual stress detection is not only an important basis for evaluating the state of key components,but also the key technology of stress control.The key metal components in the fields of aerospace,ocean shipping,rail transit and large pipeline equipment will produce residual stress during service.The magnitude and state of these residual stresses are greatly different due to different processing conditions and working conditions,and it is difficult to predict.The residual stress in the component affects the hardness,fatigue state and service life of the component,and even brittle fracture and stress corrosion cracking will occur during its service.Therefore,effective detection and evaluation of the residual stress of metal components is an important means to ensure the stable and reliable performance of key metal components.Aiming at the demand of residual stress detection,this thesis studies the electromagnetic detection system of residual stress of metal components.This thesis mainly studies the principle of stress detection of ferromagnetic materials and non-ferromagnetic materials,designs and implements an electromagnetic detection system for residual stress in metal components,builds internal stress distribution detection models,and conducts experimental research on stress detection.The main research work of this thesis are as follows:(1)The basic principle of residual stress eddy current detection method is explained.Combined the piezoresistive effect,a mathematical model and the relationship between the stress and conductivity of non-ferromagnetic materials is established.Combined with the theory of magneto-elastic effect,a mathematical model between the stress and permeability of ferromagnetic materials is established.(2)Designed and implemented a set of residual stress detection system for metal components,which solved the problems of signal acquisition and feature extraction.Using planar array magnetic sensors as sensitive components,a detection handle is designed and manufactured for data acquisition and signal conditioning.Then a highprecision signal detection platform based on FPGA+ARM architecture is built to realize signal source excitation control,data acquisition control,and signal Feature extraction and communication with the host computer.A human-computer interaction software based on Lab VIEW is developed to provide parameters and commands for the embedded system and perform stress distribution inversion and imaging.(3)The inversion study of residual stress distribution is carried out,and two types of inversion models are proposed.The sensor is calibrated according to the internal stress distribution detection model,the stress process of the specimen is analyzed,and the specimen with a fixed value of compressive stress is made.And the stress distribution model based on the amplitude information and impedance information is constructed based on the characteristics of the compression stress fixed value specimen.(4)The residual stress detection experiment is carried out,which verified the effectiveness of the detection system.The performance of the residual stress electromagnetic detection system is evaluated.The sensitivity of the sensor,the output frequency response of the sensor and the repeatability of the detection system are tested.The stress detection experiment under different stress conditions is studied.Under different stress inversion detection models,the residual stress detection experiments on laser shock-strengthened specimens is carried out The results show that the system can detect the internal residual stress of the three materials,the detection depth can reach2.2mm,the detection uncertainty is less than 30 MPa,and two-dimensional imaging can be performed on the detection results of surface residual stress and internal residual stress,and the imaging is clear and intuitive.