多层包铁结构超声反射频谱数值仿真

随着直升机技术的发展，急需对一种新型的直升机桨叶包铁结构做质量检测研究，该包铁结构外层为不锈钢，中层为橡胶、加热元件，内层为玻璃纤维。包铁结构需要分类识别的4类典型结构为上层脱粘缺陷、加热元件、下层脱粘缺陷、无缺陷无加热元件，但这种包铁结构较常见多层结构层数多、层厚薄、需识别分类多，超声波在这种结构中会发生严重的混叠现象。因此研究了超声波在薄壁多层结构中的传播规律，建立了新的包铁结构的超声反射频谱模型，将测试的不锈钢、橡胶、玻纤的声速、声阻抗、频率-衰减系数曲线、2.25 MHz和5 MHz的探头频谱代入模型进行仿真，仿真结果表明，2.25 MHz探头可以识别出包铁的4种结构，5 MHz探头可以识别出除下层缺陷的另外3种结构，实际检测结果验证了新模型的仿真结果。

Numerical Simulation of Multi-layered Iron-clad Structure UsingUltrasonic Reflection Spectrum

With the development of helicopter technology, there is an urgent need for quality inspection and research on a new type of helicopter blade iron-clad structure. The outer layer of the iron-clad structure is stainless steel, the middle layer is rubber and heating elements and the inner layer is glass fiber. The four types of typical structures that need to be classified and identified are the upper layer debonding defect, the heating element, the lower layer debonding defect, no defect and no heating element, but this kind of iron-clad structure has more layers, thinner layer thickness, more categories to be identified than the common multilayer structures, and the ultrasonic waves will have serious aliasing in this structure. Therefore, the propagation law of ultrasonic waves in the thin-walled multi-layer structure is studied, and a new ultrasonic reflection spectrum model of the iron-clad structure is established. The tested stainless, rubber, sound speed of the glass fiber, acoustic impedance, and frequency-attenuation coefficient curve, frequency spectrum of the 2.25 MHz and 5 MHz probes is brought into the model for simulation. The simulation results show that the 2.25 MHz probe can identify four structures of the iron-clad iron, and the 5 MHz probe can identify the other three structures except for the lower layer defects. The actual test results verify the simulation results of the new model.