静载拉伸和低周疲劳下Q235钢磁声发射特性

Magnetoacoustic Emission Characteristics of Q235 Steel under Static Load Tension and Low Cycle Fatigue

为揭示应力与磁声发射的关系以及明确磁声发射与铁磁性金属材料疲劳状态的关系,建立Q235钢静载拉伸的力-磁耦合模型和低周疲劳寿命模型,开展磁声发射的应用与理论研究。从有限元仿真的角度分析静载拉伸下磁声发射信号产生机理,根据低周疲劳仿真结果设计磁声发射低周疲劳试验。通过自行搭建的试验平台,验证建立的静载拉伸模型和低周疲劳模型,研究静态拉伸和低周疲劳两种状态下的磁声发射信号规律。结果表明:在静载拉伸下,在弹性范围内磁导率随着拉应力的增大呈现出线性增大的趋势,导致试件上的损耗增大,同时磁声发射信号变弱,磁声发射信号的均方根电压和包络面积呈下降趋势;在低周疲劳下,Q235钢低周疲劳寿命可以通过Smith-Watson-Topper模型进行预测,且Q235钢磁声发射信号的振幅、脉冲计数特征参数随着循环周次的增大也呈现出下降的趋势;研究成果明确了应力对磁声发射的影响以及疲劳状态对磁声发射的影响,为磁声发射的特征提取与模式识别提供了理论参考依据。

A force-magnetic coupling model of Q235 steel under static load tension and a low cycle fatigue life model are established to study the relationship between stress and magnetoacoustic emission(MAE)and the relationship between magnetoacoustic emission and fatigue state of ferromagnetic metal materials.From the perspective of finite element simulation,the generating mechanism of magnetoacoustic emission signals under static load tension is analyzed.According to the simulated results,the low cycle fatigue test of MAE is designed,and a self-built test platform is used to verify the proposed models.The law of magnetoacoustic emission signals under static load tension and low cycle fatigue was studied.The experimental results show that the permeability shows a linear increasing trend with the increase in the tensile stress in the elastic range under static tension,which leads to the increase in the loss on the specimen and the weakening of MAE signal.The root mean square voltage and envelope area of magnetoacoustic emission signal show a downward trend.However,during low cycle fatigue,the low cycle fatigue life of Q235 steel can be predicted by Smith-Watson-Topper model,and the amplitude and pulse counting characteristic parameters of Q235 steel decrease with the increase in cycle number.The obtained results clarify the influence of stress on MAE and fatigue state on MAE.