钢板表面裂纹的脉冲涡流热成像定量检测

裂纹是钢铁材料的常见缺陷之一,研究了脉冲涡流热成像技术对钢板表面裂纹的定量检测。对带有表面浅槽型裂纹的45#钢进行了感应加热实验,分析了裂纹附近的温度分布和温度响应。与温升大小相比,温度响应的曲线形态与裂纹深度间的定量关系更加清晰,曲线的形态特征可由傅里叶积分的基频相位提取。引入最小二乘支持向量机完成了裂纹几何轮廓的重构,比较了将裂纹的相位轮廓和温度轮廓分别作为支持向量机输入时的重构结果,发现相位轮廓更加适用于表面裂纹的定量检测。

Quantitative detection of steel surface crack by pulsed eddy current thermography

Cracks are one of common defects in steel materials.In this paper,the quantitative detection of steel surface cracks is studied using pulsed eddy current thermography.The 45# steel with slot cracks is inductively heated,and the temperature distribution and temperature response around cracks are analyzed.The results show that,compared with temperature rise,the quantitative relationship between the shape of temperature response curves and crack depth is clearer,and the shape of curves can be characterized by the phase of Fourier integral of temperature.The crack geometric profiles are reconstructed by the least squares support vector machine(LS-SVM).Results are compared when the input data of the LS-SVM are phase profiles and temperature profiles respectively,and it reveals that the phase profiles are more suitable for the quantitative detection of surface cracks.