基于压电阻抗技术的奥氏体不锈钢力学损伤定量监测

Quantitative Monitoring for Mechanical Damage of Austenitic Stainless Steel Based on Electro-mechanical Impedance Technique

采用压电阻抗(Electro-mechanical impedance,EMI)技术对奥氏体不锈钢在拉伸过程中的力学损伤进行了定量监测实验研究。选择不同损伤状态下阻抗谱谐振峰频率偏移量△f及均方根偏差(Root-mean-square deviation,RMSD)值作为损伤识别指数,结果表明:在试样弹性变形阶段,△f和RMSD值很小,并且在加载过程中基本保持不变或小有波动;试样发生塑性变形以后,二者均明显增加,其中,△f值由0.05kHz随加载应力逐渐增加至1.65kHz时试样发生断裂,而RMSD由1.3%增大至17.6%后逐渐减小。文中对这种差别出现的原因及两参数各自的特点进行了讨论。显微分析结果证实材料弹塑性转变过程中两参数的变化与试样微观损伤具有很好的对应性,表明利用压电阻抗技术监测和评价核电管道用奥氏体不锈钢的力学损伤具有可行性。

Mechanical damage of austenitic stainless steel used in nuclear power plant piping system and produced in tensile procedure was quantitavely monitored by EMI（Electro-mechanical impedance） technique.The resonance peak frequency shift in impedance spectrum △f and RMSD（Root-mean-square deviation） of impedance signal in different damage state were selected to compare with that in the primary state and used as damage identification indexes.It is found that both △f and RMSD can be regarded as the characteristic functions of mechanical damage.In the elastic deformation stage,the values of △f and RMSD are quite small and basiclly unchanged or small fluctuated during loading process.After entering the plastic deformation,both △f and RMSD begin to increase rapidly.The value of △f has an approximately linear relationship with the nominal tensile stress,increasing from 0.05 to 1.65 kHz till the final failure.RMSD,however,increases first from 1.3% to the maximam value 17.6%,then decreases gradually.The reason for difference explanation and the respective characteristcs of two indexes were discussed.Microscopic analysis results comfirmed that the evolution of △f and RMSD during elastic-plastic transition of austenitic stainless steel presents a strong correspondance with the microstural damage,which demonstrates the feasibility of future application of EMI in mechaniacal damage inspection and evaluation of nuclear power plant piping system.