Ultrasonic detection of melting and debonding of interface between skin and ice layer

蒙皮-冰层界面融化脱粘超声探测

College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Received: 18 April 2024

Abstract

In order to solve the problem that it is difficult to detect the local ice layer debonding when the thermal protection system is working, an on-line ultrasonic detection method for the melting degree of interface between skin and ice layer based on the theory of ultrasonic transmission in multi-layer media was studied. A multi-layer medium acoustic model including skin, water film, ice water transition layer, ice layer and air layer is constructed. Ultrasonic pulse waves with different center frequencies are used as excitation sources, and the echo signals of multi-layer medium interface are obtained by using the numerical calculation. The ultrasonic signal processing algorithm for ice melting and debonding measurement is developed. The original echo signal is processed and the characteristic parameters of the echo signal of interface between skin and ice layer are extracted. The ultrasonic reflection coefficient of interface between skin and ice layer is proposed to evaluate the degree of ice melting. The ultrasonic ice detection system was built, and the low-temperature ultrasonic sensor was designed and fabricated. The ability of the system to measure the degree of ice melting under the action of electric heating was verified in the low-temperature environment. The ultrasonic ice detection system was built, and the low-temperature ultrasonic sensor was designed and fabricated. The ability of the system to measure the degree of ice melting under the action of electric heating was verified in the low-temperature environment. The theoretical results show that when the ice on the skin melts and produces a thin water film, the degree of ice melting can be reflected by the change of ultrasonic reflection coefficient at the skin-attachment interface. In this paper, the ultrasonic reflection coefficient more than 0.8 is used as the criterion of ice melting. With the increasing of center frequency of the ultrasonic signal, the thinner water film can be identified. The identification thickness of the water film corresponding to 7.5 MHz center frequency signal is 10 μm. The experimental results show that under the conditions of clear ice, mixed ice and frost ice, the ultrasonic detection system can out-put the ice layer debonding signal at the initial stage of electric heating. The propagation characteristics of ultrasonic pulse wave of interface between skin and ice layer in the thermal protection are preliminarily explored. The present method for detecting the degree of ice melting is expected to further reduce the energy consumption of thermal protection.

摘要

为解决热防护系统工作时局部冰层脱粘难以在线探测的问题, 开展了基于多层介质内超声传递理论的蒙皮-冰层界面融化程度在线超声探测方法研究。构建了包含蒙皮、水膜、冰水过渡层、冰层和空气层的多层介质声学模型, 采用不同中心频率的超声脉冲波作为激励源, 通过数值计算获得多层介质界面回波信号; 发展用于冰层融化脱粘测量的超声信号处理算法, 对原始回波信号进行处理并提取蒙皮-冰层界面回波信号特征参数, 提出采用蒙皮-冰层界面超声反射系数评估冰层融化程度; 搭建超声结冰探测系统, 设计并制备耐低温超声传感器, 在低温环境验证电加热作用下系统对冰层融化程度的测量能力。理论研究结果表明: 当蒙皮表面冰层融化产生薄水膜时, 可通过蒙皮-附着物界面超声反射系数变化反映冰层融化程度; 将超声反射系数大于0.8作为冰层融化判据, 随超声信号中心频率增大, 可对更薄的水膜进行识别, 7.5 MHz中心频率信号对应的水膜识别厚度为10 μm。实验研究结果表明, 在明冰、混合冰和霜冰结冰气象条件下, 超声探测系统均可在电加热工作初期输出冰层脱粘信号。初步探索了热防护作用过程中蒙皮-冰层界面超声脉冲波传播特性, 提出的冰融化程度探测方法有望进一步降低热防护能耗。