Time reversibility of Lamb waves in thin plates with surface-bonded piezoelectric transducers is temperature invariant at the best reconstruction frequency

Abstract

The Lamb wave time-reversal method has been widely proposed as a baseline-free method for damage detection in thin-walled structures. Under varying thermal environments, it would require that the time reversibility of Lamb waves is temperature invariant. In this study, we examine the temperature dependence of Lamb waves and its time reversibility using experiments and finite element simulations on isotropic plates with surface-bonded piezoelectric wafer transducers for actuation and sensing. The study is conducted at three different temperatures of the system from 25°C to 75°C for a wide range of excitation frequency. The results indicate that the time reversibility can undergo significant changes due to temperature variations depending on the excitation frequency. However, at the best reconstruction frequency corresponding to the maximum similarity of the reconstructed signal with the original input signal (proposed recently as the probing frequency), the change in the percent similarity with temperature is insignificant. The results also demonstrate that changes in the physical properties of both adhesive layers and piezoelectric transducers with temperature play a dominant role in influencing Lamb wave amplitudes. However, only the change in the characteristics of the adhesive layers is responsible for the temperature dependence of the time reversibility of Lamb waves.

Baseline-free damage detection and sizing under varying temperatures using Lamb waves without temperature compensation

“…Various subsequent studies 43,44,50 have since established the efficacy of the RTRM using f rc and the extended wave packet in room temperature.…”

“…Lamb waves were generated in the plate by exciting one of the transducers with a five-cycle Hann window modulated sinusoidal tone burst signal of 20 V peak amplitude. 44 The central frequency of the input excitation was chosen with in a range such that it actuates only S 0 and A 0 modes. The voltage of the top electrode of the other transducer (sensor) was recorded after applying a 10 dB gain with a sampling frequency of 72 MS/s.…”

Role of transducer inertia in generation, sensing, and time-reversal process of Lamb waves in thin plates with surface-bonded piezoelectric transducers

“…For further validation, the present solution is also compared with the experimental results presented by Sharma et al (2020) for a similar system as in Figure 3 with the same plate and adhesive layer thickness but with transducers of 0.25 mm thickness. The transducer size used in the experiment is 10 mm, but a reduced size of 9 mm is considered for the 2D FE simulation and the analytical solution to compensate for the possible weak bonding around the edges of the transducer in the experimental set-up (Sharma et al, 2020).…”

“…For further validation, the present solution is also compared with the experimental results presented by Sharma et al (2020) for a similar system as in Figure 3 with the same plate and adhesive layer thickness but with transducers of 0.25 mm thickness. The transducer size used in the experiment is 10 mm, but a reduced size of 9 mm is considered for the 2D FE simulation and the analytical solution to compensate for the possible weak bonding around the edges of the transducer in the experimental set-up (Sharma et al, 2020). A recent study (Agrahari and Kapuria, 2016a) has shown that although a full-field 3D FE solution differs from the simplified plane strain 2D FE solution in terms of actual magnitude of the voltage response, the two solutions match well when they are normalized with respect to their respective peaks.…”

“…The peak amplitudes of the waveforms in the response signal are obtained from its Hilbert envelope (Sharma et al, 2020). For both S 0 and A 0 modes, the inclusion of the inertia term of each constituent element increases the peak amplitude in the frequency range considered.…”