To address the urgent demand for active guided wave damage monitoring of multilayer heterogeneous structures of aerospace vehicles under complex service conditions, we conduct a simulation study on piezoelectric guided waves in multilayer heterogeneous structures. By establishing a high-precision simulation model of multi-physics field coupling, the propagation characteristics and attenuation laws of guided waves in multilayer heterogeneous structures are revealed, which provides a design basis for the implementation of guided wave monitoring methods. Firstly, a multi-physics field coupling finite element model considering material attenuation characteristics is established, and the attenuation effect of viscoelastic layers on guided waves is simulated by Rayleigh damping. Secondly, the meshing strategy of multilayer heterogeneous structures is optimized to balance the calculation accuracy and efficiency. Experimental verification shows that the proposed method accurately simulates the attenuation behavior and propagation phase of guided waves, significantly improving the simulation accuracy. After introducing the damping model, the amplitude attenuation errors of S₀ and A₀ modes in the structure are reduced from 122.3% and 78.1% to 3.4% and 3.6% respectively; the mesh optimization reduces the element degrees of freedom by 66.6% while keeping the phase error within 0.6%. This research provides a high-precision simulation method and theoretical basis for damage monitoring of aerospace multilayer heterogeneous structures, which has important engineering value for ensuring the safe service of aerospace vehicles.

It is well recognized that Structural Health Monitoring (SHM) reliability evaluation is a key aspect that needs to be urgently addressed to promote the wide application of SHM methods. However, the existing studies typically transfer the Non-Destructive Testing/Evaluation (NDT/E) reliability metrics to SHM without a systematic analysis of where these metrics originated. Seldom attentions are paid to the evaluation conditions which are very important to apply these metrics. Aimed at this issue, a new condition control-based Dual-Reliability Evaluation (Dual-RE) method for SHM is proposed. This new method is proposed based on a systematic analysis of the whole framework of reliability evaluation from instrument to NDT, and emphasis is paid to the evaluation condition control. Based on these analyses, considering the special online application scenario of SHM, the proposed Dual-RE method contains two key components: Integrated Sensor-based SHM-RE (IS-SHM-RE) and Critical Service Condition-based SHM-RE (CSC-SHM-RE). IS-SHM-RE evaluates the reliability of integrated SHM sensor and system themselves under approximate repeatability conditions, while CSC-SHM-RE assesses SHM reliability under the dominant uncertainties during service, namely intermediate conditions. To demonstrate the Dual-RE, crack monitoring by using the Guided Wave-based-SHM (GW-SHM) on aircraft lug structures is taken as a case study. Both the crack detection and sizing performance are evaluated from accuracy and uncertainty.

The engineering applications of Structural Health Monitoring (SHM) methods have become more and more popular, and their application in the aerospace field has been gradually developed. However, but there is still no widely recognized standard on how to evaluate their reliability. In recent years, both academia and industry have made many explorations on how to develop SHM reliability evaluation methods, and the Non-Destructive Testing (NDT) reliability evaluation method has been used as a starting point for SHM reliability evaluation. However, SHM is significantly different from NDT both in terms of system realization and application mode, and the reliability evaluation of SHM has yet to be thoroughly studied. This paper reviews the reliability evaluation methods from NDT to SHM. The development of NDT reliability evaluation method, the application of NDT evaluation method on SHM, the difference between SHM and NDT reliability evaluation, and the development of the SHM reliability evaluation method are discussed with the current research status. Based on this, a condition control-based dual-reliability evaluation for SHM is proposed, and concludes with a summary and prospect.

Structural health monitoring-based quantitative damage diagnosis technique plays a key role in real-time condition monitoring. Among the current research, piezoelectric (PZT) sensor and Guided Wave (GW) based damage quantification methods are promising, which normally establish a calibration model between GW feature and damage degree by experiments on batch specimens, and then conduct the calibration model on the monitored specimen. However, the accuracy of PZT and GW based damage quantification is affected by dispersion introduced by sensor network performance, structural material, and damage propagation among the adopted batch specimens. For improving the accuracy of damage quantification, this paper adopts PZT layer as sensor network and creatively implements theoretical and experimental research on batch PZT layers consistency control. On one hand, a two-level consistency control method based on multidimensional features-Euclidean distance is proposed to ensure the performance consistency of PZT layers placed on different specimens. On the other hand, experimental research on typical aircraft lug structures is also carried out to evaluate the requirement on performance consistency of PZT layers when performing quantitative damage diagnosis, and further verify the proposed two-level consistency control method. Experimental results show that the accuracy of damage quantification raises by 38% when the dispersion of different PZT layers is controlled within 5%.