复杂型面叶片由于其结构复杂, 缺陷检测困难, 针对这类叶片的无损检测研究一直是国内外关注的热点。文中基于超声激励下含缺陷介质的摩擦生热模型, 分析缺陷处的热流传导, 推导了含裂纹叶片简化模型的表面温度场。针对复杂型面叶片裂纹处的生热模型, 应用有限元方法进行了数值仿真。仿真结果表明, 激励时间越长, 裂纹缺陷区域温升越大; 温升速率随时间增加呈先上升后下降的趋势。利用超声红外热成像检测平台, 对含裂纹的汽轮机叶片进行检测。实验结果表明, 当预紧力处于100~150 N时, 裂纹区域生热最明显, 叶片裂纹检测效果最好。基于数值仿真和实验表明, 超声红外热成像技术可以有效地检测出复杂型面叶片中的裂纹缺陷,具有一定的工程指导意义和广泛应用前景。

It is difficult to detect the defects in blades with complex profile due to the complex structures, thus nondestructive testing on this type blade has attracted abundant attentions around the world. In this paper, based on the frictional heat generation model of the defect-containing medium under ultrasonic excitation, the heat flow conduction was analyzed and the surface temperature field of the simplified model about cracked blades was derived. For the heat generation in cracked fields of blades with complex profile, finite element method was applied to numerical simulation. According to the simulation result, the longer the excitation time was, the greater the temperature rise in the crack defect field was; the rate of temperature rise presented a trend that the rate rose first and then fell with time. The steam turbine blade with a crack was tested by the detecting platform of ultrasonic infrared thermal imaging. The result of test shows that the heat generation field is most obvious in the cracked field and the result is most clear for the crack in this blade when the preload is from 100 N to 150 N. According to the numerical simulation and test, ultrasonic infrared thermal imaging technology can efficiently detect cracks defect in blades with complex profile, it has a definite guiding significance on engineering and a broad application prospect.