IEEE Trans Ultrason Ferroelectr Freq Control. 2017 Oct;64(10):1573-1582. doi: 10.1109/TUFFC.2017.2726819. Epub 2017 Jul 13.
Progress in computational fluid dynamics and the availability of new composite materials are driving major advances in the design of aerospace engine components which now have highly complex geometries optimized to maximize system performance. However, shape complexity poses significant challenges to traditional nondestructive evaluation methods whose sensitivity and selectivity rapidly decrease as surface curvature increases. In addition, new aerospace materials typically exhibit an intricate microstructure that further complicates the inspection. In this context, an attractive solution is offered by combining ultrasonic phased array (PA) technology with immersion testing. Here, the water column formed between the complex surface of the component and the flat face of a linear or matrix array probe ensures ideal acoustic coupling between the array and the component as the probe is continuously scanned to form a volumetric rendering of the part. While the immersion configuration is desirable for practical testing, the interpretation of the measured ultrasonic signals for image formation is complicated by reflection and refraction effects that occur at the water-component interface. To account for refraction, the geometry of the interface must first be reconstructed from the reflected signals and subsequently used to compute suitable delay laws to focus inside the component. These calculations are based on ray theory and can be computationally intensive. Moreover, strong reflections from the interface can lead to a thick dead zone beneath the surface of the component which limits sensitivity to shallow subsurface defects. This paper presents a general approach that combines advanced computing for rapid ray tracing in anisotropic media with a 256-channel parallel array architecture. The full-volume inspection of complex-shape components is enabled through the combination of both reflected and transmitted signals through the part using a pair of arrays held in a yoke configuration. Experimental results are provided for specimens of increasing complexity relevant to aerospace applications such as fan blades. It is shown that PA technology can provide a robust solution to detect a variety of defects including porosity and waviness in composite parts.
计算流体动力学的进展和新型复合材料的可用性正在推动航空航天发动机部件设计的重大进展，这些部件现在具有高度复杂的几何形状，经过优化以最大限度地提高系统性能。然而，形状的复杂性给传统的无损评估方法带来了重大挑战，这些方法的灵敏度和选择性随着表面曲率的增加而迅速降低。此外，新型航空航天材料通常具有复杂的微观结构，这进一步增加了检查的复杂性。在这种情况下，将超声相控阵（PA）技术与浸入式测试相结合是一个有吸引力的解决方案。在这里，组件复杂表面和线性或矩阵阵列探头的平面之间形成的水柱确保了阵列和组件之间的理想声学耦合，因为探头不断扫描以形成部件的体积渲染。虽然浸入式配置适合实际测试，但由于在水-部件界面处发生的反射和折射效应，测量的超声信号的解释对于图像形成变得复杂。为了考虑折射，必须首先从反射信号重建界面的几何形状，然后使用它来计算适合在组件内部聚焦的合适延迟定律。这些计算基于射线理论，可能计算量很大。此外，来自界面的强烈反射会导致组件表面下方出现厚的死区，从而限制了对浅层表面下缺陷的灵敏度。本文提出了一种通用方法，该方法将快速射线追踪的先进计算与 256 通道并行阵列架构相结合。通过使用轭式配置中的一对阵列组合穿过部件的反射和透射信号，可以实现对复杂形状部件的全体积检查。提供了越来越复杂的航空航天应用相关样本的实验结果，例如风扇叶片。结果表明，PA 技术可以提供一种可靠的解决方案，用于检测各种缺陷，包括复合材料部件中的孔隙率和波纹度。
