The Application of Voltage Amplifiers in the Study of Interface of Composite Structures Based on Nonlinear Piezoelectric Ultrasound
Composite structures are an important type of structure with very wide applications. For composite structures, the bond between steel and concrete is the prerequisite for ensuring that the two materials can work together. Once the bond is lost, it poses a serious threat to the safe use of the composite structure. Therefore, it is crucial to use effective detection methods to monitor the debonding state of composite structures in a timely and accurate manner. At present, the use of piezoelectric wave methods to assess the service condition of composite structures has achieved fruitful results. However, since traditional linear ultrasonic testing methods are not sensitive to early debonding damage at the interface of composite structures, there is an urgent need for more sensitive methods to identify early debonding damage at the interface of composite structures. Vibro-acoustic modulation (VAM) is a detection technology based on nonlinear acoustic theory that can identify damage at the micron and even nanometer levels. This study mainly focuses on the identification of early debonding damage in steel-concrete composite slabs (SCCS) and combines piezoelectric ceramics with VAM technology to achieve nonlinear modulation of two acoustic fields at the damage site. Using the nonlinear VAM principle, a damage index is derived to identify debonding damage and quantitatively assess the damage trend.
By studying the application of VAM technology in the early debonding damage monitoring of SCCS, the sensing signals obtained are analyzed in the time-frequency domain, and specific parameters representing the damage are derived based on nonlinear acoustic theory, achieving the goal of identifying and assessing early debonding damage in SCCS. According to the theoretical derivation under the mixed acoustic field and related simulation calculations, it is found that when the SCCS is in good bond condition, the nonlinear damage is not obvious, and the time-frequency domain map of the sensing signal shows a linear superposition of the two acoustic fields. When debonding damage occurs in the SCCS, the nonlinearity is significantly enhanced, and a modulation effect occurs at the damage site. Based on the theoretical analysis results, a VAM monitoring system was designed and built, and relevant studies were carried out on this experimental platform to verify that the VAM method is effective in detecting early debonding damage in SCCS. The key to the experiment is to use nonlinear VAM technology to detect debonding damage in SCCS and obtain the corresponding nonlinear parameters, which are required to reflect the damage state and exclude the nonlinear effects of the experimental platform. Studies have shown that the monitoring algorithm based on nonlinear VAM can effectively identify micron-level debonding damage and is robust to excitation parameters, providing a highly sensitive non-destructive testing method for the health monitoring of composite structure interfaces.
Experiment Name: Research on Debonding Monitoring Method of Composite Structure Interfaces Based on Nonlinear Piezoelectric Ultrasound
Experiment Principle: The principle is based on the vibration-acoustic modulation (VAM) method in nonlinear piezoelectric ultrasonic technology, aiming to detect early debonding damage at the interface of steel-concrete composite slabs (SCCS). The core principle is to apply low-frequency (LF) and high-frequency (HF) acoustic wave excitation signals simultaneously and use the modulation phenomenon caused by the nonlinear contact effect at the damage interface to extract characteristic parameters related to the damage. Specifically, the LF signal (e.g., 1.5 kHz) acts as the pump wave, applied to the structure surface by a shaker, causing periodic opening and closing vibrations at the debonding interface. The HF signal (e.g., 50 kHz) serves as the probe wave, excited by piezoelectric ceramics (PZT) and propagating along the structure surface. When the HF wave passes through the debonding damage area, the interface's nonlinear vibration driven by the LF signal modulates its propagation path and energy distribution, resulting in sideband components (fHF±nfLF, where n is an integer) in the high-frequency signal spectrum, the amplitude of which is directly related to the degree of interface damage.
The experiment verifies this principle through three stages: theoretical modeling, finite element simulation, and physical testing. At the theoretical level, based on the elastic wave equation and contact nonlinearity model, the mathematical expression of the sideband signal is derived, revealing the mechanism of the influence of the damage interface's stiffness nonlinearity on the modulation effect. At the simulation level, using ABAQUS, a two-dimensional model of SCCS is established to simulate the wave propagation behavior under different debonding areas, depths, and excitation parameters. It is found that when the LF frequency is close to the structure's natural frequency (e.g., 1460 Hz), the interface opening and closing are most significant, the sideband amplitude increases linearly with the LF amplitude, and the HF amplitude tends to saturate after a threshold (about 6 V). At the experimental level, a monitoring platform composed of a shaker, piezoelectric sensors, a function generator, and an oscilloscope is built. By comparing the frequency domain responses of healthy and damaged specimens, it is found that the first-order sideband amplitude on the damaged side can reach 92 times that of the healthy side, and the modulation index (MI) significantly increases with the increase of LF amplitude (from -98 dB to -79 dB). In addition, the nonlinear coefficient (K') increases threefold with the increase of debonding area and then stabilizes, while the debonding depth shows a "growth-decay-stabilization" three-stage pattern. Finally, the reliability of the model is verified by the measured Rayleigh wave speed (2400-2415 m/s) and theoretical error (<5%), indicating that VAM technology can effectively identify micron-level debonding damage by capturing nonlinear modulation characteristics, providing a highly sensitive non-destructive testing method for the health monitoring of composite structures.
Experiment Block Diagram:
Experiment Process: First, before pouring concrete, the damage location is determined on the steel plate surface, and butter is sprayed to simulate interface debonding. Piezoelectric ceramic sensors are also bonded to the outer surface of the steel plate at specified locations for signal excitation and reception. Subsequently, a vibration-acoustic modulation monitoring system is built, which includes key equipment such as a shaker, a function generator, a power amplifier, an oscilloscope, and piezoelectric ceramic chips. Based on theoretical analysis and simulation calculations, the frequencies and amplitudes of the low-frequency (LF) and high-frequency (HF) signals are selected. The shaker generates the LF signal, and the piezoelectric ceramic chip generates the HF signal. These signals interact at the interface of the composite structure, simulating the nonlinear modulation effect at the damage site. Next, the sensing signal received by the piezoelectric ceramic chip is collected by the oscilloscope, and the signal is analyzed in the time-frequency domain to extract characteristic parameters for damage identification. Finally, based on nonlinear ultrasonic theory, the changes in the extracted characteristic parameters are analyzed to identify the presence and extent of damage.
Application Directions: Cell sorting, non-destructive testing, dielectrophoresis, electroluminescent device testing
Application Scenarios: Nonlinear ultrasonic technology, vibration-acoustic modulation (VAM), early debonding monitoring, nonlinear characteristic parameters, damage assessment algorithm, finite element analysis, debonding of composite structure interfaces, piezoelectric ceramics, steel-concrete composite slabs (SCCS)
Voltage Amplifier Product Recommendation: ATA-2000 Series High-Voltage Amplifiers
Figure: Specifications of the ATA-2000 Series High-Voltage Amplifiers
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