Research on characterization of cumulative plastic damage in butt weld under low cycle fatigue using metal magnetic memory
Steel members under seismic load often suffer from severe fracture damage due to the accumulation of plastic damage caused by low cycle fatigue.As an emerging nondestructive testing technology,metal magnetic memory has been proven to be useful for the fatigue damage characterization of steel members.In order to overcome the limitations of current magneto-mechanical coupling theories and numerical simulations,and enable nondestructive evaluation of plastic damage in welded specimens,magnetic memory technology was used to characterize the cumulative plastic damage of butt welds subjected to low cycle fatigue.A magneto-mechanical coupling finite element simulation of welded specimens was conducted to address the issue of non-uniform magnetization in welded components,utilizing an improved simulation method based on an existing theoretical model.Moreover,the variation law and characteristic parameters of normal magnetic signal HSF(z)on the surface were studied through low cycle fatigue and magnetic signal detection tests for the Q345qC welded specimen.Based on the experimental and simulation results,it is clear that the HSF(z)signal curve exhibits a noticeable sudden change at the welding location.Additionally,the gradient of the peak-valley(Kp-v)decreases exponentially with the progressive accumulation of plastic damage(D).The experimental and simulation methods have an average error of less than 5％,demonstrating their accuracy.A quantitative relationship for Kp-v-D in welded specimens was established,validating that Kp-v has the ability to reflect the cumulative plastic damage of steel when subjected to low cycle fatigue.This provides a benchmark for the quantitative evaluation of cumulative plastic damage of welded parts.
low cycle fatiguecumulative plastic damagemetal magnetic memorymagneto-mechanical couplingdamage characterization
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