Research On Quantitative Measurement Of Ferromagnetic Components Based On ACSM

Stress is one of the important factors that affected the material fatigue,stress corrosion resistance,dimensional stability and service life of ferromagnetic.It is essential to detect stress for preventing deformation and fracture critial that caused by stress concentration. Some methods have been applied to the stress measurement,but they all have some limitations,then a new kind of electromagnetic non-destructive testing methods-alternating current stress measurement(ACSM) has been used to develop the stress measurement.Based on the basic the theory of ferromagnetics,we studied the relative topics systematically,the relevant research and discussion for the stress measurement have been carried out by combining the test.Firstly,starting from the basic characteristics of ferromagnetic material,this paper analyzed the mechanical properties of the material.according to the thermal equilibrium conditions,we studied the stress detection principle of ACSM and the effects of stress on magnetic properties of ferromagnetic materials from the perspective of energy,which provided a theoretical basis for ACSM.Secondly this paper introduced the design of the entire ACSM detection system,including the drive module,sensor,signal conditioning modules and PC software based on LabVIEW.Finally,the typical ferromagnetic materials of Q235 steel has been taken as the research object,the effective feature volume of stress evaluation was determined by static tension.then the effect of different excitation frequency,different excitation voltage and different coil turns on testing signal were studied.The results showed that:the real part of testing signal linearly with the increase of the stress,which can be used to assess the value of ferromagnetic component stress.in addition,an optimal testing parameters are obtained by comparing and analyzing the coefficient and sensitivity obtained from curve fitting.In this parameters,the linearly dependent coefficient is 0.991 and the sensitivity is 7.411mV/kN.then the measurement of stress was carried out,which related to tensile specimens and welded specimens.the measurements of ACSM were compared with the blind-hole method.the results showed that:for tensile specimens,the measured dates have a good consistency.for welded specimens,most of the difference between the two methods is less than 30 MPa, the relative error <20%,which certifiedthat ACSM has high accuracy.Finally carry out different types of weld joints at different locations and measurement of residual stress test, the results showed that: the closer from the solder joints, the greater the stress value.With the increase of distance from the center of solder joints, the stress decreases.when the distance is more than 30 mm, the stress value is not affected by the size of the solder joints.