Modeling of pitting damage-induced ultrasonic nonlinearity in AL-Whipple shields of spacecraft: Theory, simulation, and experimental validation

• Published in: International journal of mechanical sciences Vol. 207; p. 106659
• Main Authors: Cao, Wuxiong, Xu, Lei, Su, Zhongqing, Pang, Baojun, Chi, Runqiang, Wang, Lei, Wang, Xiaoyu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2021
• Subjects: Finite element modeling; Hypervelocity impact; Pitting damage; Quantitative characterization; Ultrasonic nonlinearity; Ultrasonic nonlinearity; Finite element modeling; Quantitative characterization; Pitting damage; Hypervelocity impact
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2021.106659

•Proposed a dedicated modeling technique to scrutinize the modulation mechanism of various modalities of pitting damage on the probing ultrasonic waves, including craters, cracks and dislocation plasticity;•Established a quantitative correlation between the nonlinear features (i.e., second harmonics) of ultrasonic waves and all possible nonlinear sources attribute of different types of pitting damage;•In-depth, quantitative and detailed characterization of hypervelocity impact-induced pitting damage via the proposed approach;•Dedicated numerical simulations and nonlinear characterization experiments, with results corroborated by theoretical prediction;•Use of a typical dual-layered Whipple shield for experimental validation, with results benefiting real-world space applications. Pitting damage in the Whipple shield of spacecraft, engendered by a hypervelocity impact (HVI, exceeding 3.0 km/s), is a specific damage modality in large-scale spacecraft (e.g., Space Station). Typically, it features multitudinous craters and cracks disorderedly scattered over a wide region, accompanied with a diversity of microstructural damages (e.g., dislocation plasticity, micro-voids and cracks) . This damage modality induces highly complex, mutually-interfering wave scattering in the received ultrasonic waves, making signal interpretation a daunting task, let alone the quantitative characterization of a pitted region. With this motivation, a dedicated modeling technique is proposed to scrutinize the modulation mechanism of various modalities of pitting damage on the probing ultrasonic waves, based on retrofitted nonlinear constitutive equations by comprehensively considering all nonlinearities originated from different damage sources (e.g., inherent material imperfections, as well as the above HVI-induced intensified plasticity and micro-cracks, etc.). On this basis, a quantitative correlation between the nonlinear features (i.e., second harmonics) of ultrasonic waves and the pitting damage severity is established. The modeling technique is experimentally corroborated, and the results demonstrate good consistency in between, revealing that: (1) the proposed modeling approach is feasible to faithfully simulate and precisely evaluate pitting damage-incurred nonlinearities manifested in ultrasonic waves; (2) the ultrasonic nonlinearity intensifies with the increase of pitting damage severity; and (3) the detection sensibility and cumulative effect of second harmonics are related to the “internal resonance” conditions, representing by the excitation frequency. This study yields a structural health monitoring strategy for accurately characterizing pitting-type damage at an embryo stage and surveilling material deterioration progress continuously. Exploiting the higher sensitivity of nonlinear attributes of guided ultrasonic waves, a dedicated modeling technique is developed to scrutinize the modulation mechanism of various modalities of pitting damage on the probing ultrasonic waves, with capacity of characterizing the hypervelocity impact induced-pitting damage in an in-situ, accuracy and quantitative manner. [Display omitted]