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PVDF piezoelectric sensor: (a) schematic structure of PVDF foil piezoelectric transducer; (b) PVDF foil piezoelectric transducer physical picture.
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In this paper, a polyvinylidene fluoride (PVDF) piezoelectric transducer was developed to detect laser-induced surface acoustic waves in a SiO(2)-thin film-Si-substrate structure. In order to solve the problems related to, firstly, the position of the probe, and secondly, the fact that signals at different points cannot be detected simultaneously d...
Similar publications
In this paper a possibility of determining a local velocity of the surface acoustic Rayleigh waves using a transducer, with the rigidly connected emitting and receiving parts, is considered. A problem on spatial resolution of such a transducer for investigation of inhomogeneous specimens is also examined. A high spatial resolution can be obtained d...
Citations
... In our previous paper [8], an in-depth review of the use of PVDF to measure dynamic forces in static structures [4,[9][10][11][12][13][14][15][16] was discussed. It was noted that PVDF cannot measure absolute pressures, only the fluctuations, which is a common use of PVDF in fluids [17][18][19][20][21][22], due to its piezoelectric properties [23,24]. The paper reported on the use of PVDF inside a thrust bearing to measure the pressure fluctuations and infer the change in contact force. ...
In our previous work we demonstrated the feasibility of using Polyvinylidene Fluoride (PVDF) sensors inside an operational thrust bearing and were able to measure the blade passing frequencies (BPF) due to an asymmetric flow around different propellers. In that work however the sensors were positioned inside the flat surface of the stationary portion of the bearing with the tilted pads rotated on the opposite side. Due to this configuration the output signal of the PVDF consisted of a superposition of the pad passing frequency (PPF) and the blade passing frequency (BPF) making it difficult to extract useful information from the results. Here, an improved bearing pad-film configuration is proposed in order to minimise the effects of the PPF. By embedding the films inside the pads, positioned on the stationary side of bearing, and rotating the flat surface, it was possible to eliminate the PPF and significantly increase the signal to noise ratio. The measured results give a better understanding of the fundamental vibratory components that arise from the propeller-shaft system.
... van Tol and Hughes made an underwater sound-intensity probe using PVDF material [8]. Lu et al. made PVDF sensors and used them to detect surface acoustic waves [9]. By measuring its linearity, Yuan et al. demonstrated that PVDF piezoelectric film is highly suitable for measuring dynamic pressure [10]. ...
... The results of the two experiments were highly consistent, and thus the results of only Experiment 1 have been described here. The spectra of the voltage output (represented by log(V), log( ) = log( 1Volt ), using a reference level of one volt) at different wind speeds (9,14,18,21,24 and 27 m/s) are shown in Figure 13. ...
To measure the flow velocity of a fluid without affecting its motion state, a method was proposed based on a polyvinylidene fluoride (PVDF) piezoelectric film sensor. A self-made PVDF piezoelectric sensor placed parallel with the flow direction was used to measure the flow velocity. First, the piezoelectric characteristics of PVDF were obtained theoretically. Next, the relationship between flow velocity and sound pressure was verified numerically. Finally, the relationship between flow velocity and the electrical output of the PVDF piezoelectric film was obtained experimentally. In conclusion, the proposed method was shown to be reliable and effective.
... In addition, PVDF films are very low cost, compared with PZTs. PVDF films have found many applications [47][48][49][50][51], including structural health monitoring [52]. Shirinov et al. developed a pressure sensor with PVDF film as the sensing element and studied the sensing performance of the sensor [53]. ...
Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force–time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.
... Regarding tentative experimental LSAW detection techniques to be applied for further testing a sample of human skin, optical and piezoelectric detection methods may be suitable [6,20], however, piezoelectric approach may be not appropriate for such soft materials as skin, therefore, optical detection is then selected. In Table 3, a list of criteria and recommendations to best generate LSAWs in both aspects, the simulation and the optical experimental technique, are proposed. ...
... This approach uses the dispersion curve analysis in the frequency domain. 18,19 In order to calculate the phase velocity and plot the dispersion curve, two signals containing the information of the vertical displacements of the simulated SAWs in two different locations are needed. The two receiving points for detecting these signals are located at 3 mm (arrow A in Fig. 6) and 3.5 mm (arrow B in Fig. 6) from the left boundary of the model where the laser beam input signal is applied. ...
Air pollution has been correlated to an increasing number of cases of human skin diseases in recent years. However, the investigation of human skin tissues has received only limited attention, to the point that there are not yet satisfactory modern detection technologies to accurately, noninvasively, and rapidly diagnose human skin at epidermis and dermis levels. In order to detect and analyze severe skin diseases such as melanoma, a finite element method (FEM) simulation study of the application of the laser-generated surface acoustic wave (LSAW) technique is developed. A three-layer human skin model is built, where LSAW’s are generated and propagated, and their effects in the skin medium with melanoma are analyzed. Frequency domain analysis is used as a main tool to investigate such issues as minimum detectable size of melanoma, filtering spectra from noise and from computational irregularities, as well as on how the FEM model meshing size and computational capabilities influence the accuracy of the results. Based on the aforementioned aspects, the analysis of the signals under the scrutiny of the phase velocity dispersion curve is verified to be a reliable, a sensitive, and a promising approach for detecting and characterizing melanoma in human skin
... As shown in Fig. 1, SAW excitation methods can be classified by the main source that produces the surface waves, such as pulse laser excitation in the Laser-generated Surface Acoustic Wave technique (LSAW) [23][24][25], InterDigital Transducer (IDT) [26,27], PieZoelectric Transducer (PZT) [28,29] and ElectroMagnetic Acoustic Transducer (EMAT) [30,31]. On the other hand, the detection methods include using pulse/continuous laser [23][24][25], IDT [26,27], PZT [16][17][18]32], EMAT [33,34], aircoupling transducer [35,36], and capacitance transducers [37]. ...
... Within these approaches, the piezoelectric transducer approach is the most commonly used method. Piezoelectric transducers, such as piezoelectric ceramic, piezoelectric crystal and piezoelectric film [16][17][18]32], usually require using a wedge to be implemented. The use of PolyVinyliDene Fluoride (PVDF) piezoelectric film is still one of the best ways of detecting SAWs. ...
In this paper, the principle of surface acoustic wave techniques and their application to the monitoring of cracks are presented and compared to other classic non-destructive techniques. A practical classification of methods regarding the excitation and detection of surface acoustic waves is enumerated, among them, laser-generated surface acoustic wave technique is carefully analyzed as a prospective technique, and two important detection methods using piezoelectric and light deflection are described. Then, the strategies and variables used in crack monitoring based on laser-generated surface acoustic wave technique are reviewed. To achieve the goal of quantitative detection of cracks, most researchers use numerical models and experiments to characterize main crack features. Discussions and prospective approaches for further quantitative monitoring of cracks are provided.
... Moreover, piezoelectric foil transducers can be homemade easily [18]. For our experimental setup, a number of simple foil piezoelectric transducers were homemade, as well as innovative foil piezoelectric transducer structures [19]. ...
The present paper presents the design and development results of a system setup for measuring Young's modulus of thin films by laser-induced surface acoustic waves based on the integration of two detection methods, namely, piezoelectric transducer detection and differential confocal detection, which may be used for conducting consecutive or simultaneous measurements. After demonstrating the capabilities of each detection approach, it is shown how, depending on a wider range of applications, sample materials and measurement environments, the developed integrated system inherits and harnesses the main characteristics of its detection channels, resulting in an more practical and flexible equipment for determining Young's modulus than traditional nanoindentation equipment, and also suitable for cross-validation purposes.
The present paper is concerned with the Rayleigh wave propagation in the machined surface with a thin damaged layer with residual stress. We assume that the layer and the half-space are bonded perfectly to each other. Biot’s theory of small deformations influenced by initial stress forms the basis for this study. With the help of the effective boundary condition method, a third-order approximate secular equation of Rayleigh waves is established for the case that the layer and half-space are both orthotropic. In addition, an explicit third-order approximate formula for the Rayleigh wave velocity is derived from the secular equation. By considering a sample of silicon wafer by fine grinding with fine abrasive grains, the accuracy of the approximate formula has been verified. This study is meant to serve as the mathematical foundation for non-destructive testing of residual stress in the practical applications.
A polyvinylidene fluoride (PVDF) film-assisted optical fiber cantilever-based acoustic sensor with high sensitivity is presented for low-frequency applications. The sensing cantilever is fabricated by developing a PVDF film on a bare optical fiber. The light is coupled from an input fiber to the output cantilever fiber using the butt-coupling method. The end tip of the input fiber is mounted on a fixed holder, while the output fiber-PVDF cantilever is free to vibrate. The acoustic pressure vibrates the fiber-PVDF cantilever, which causes the change in transmitted power. The sensor’s output is measured in terms of variation in the output light intensity. An advanced double cantilever method is also demonstrated to improve the sensor’s sensitivity, which delivers two natural frequencies with high signal amplitude. The sensitivity of the PVDF-assisted fiber cantilever is observed as 958 mV/Pa or -0.37 dB re 1 V/Pa, which is significantly better than the bare optical fiber cantilever having a sensitivity of 5 mV/Pa or -46 dB re 1 V/Pa at the resonance frequency. The dynamic range of the sensor is 100 Hz to 4000 Hz with a minimum detectable pressure (MDP) of 0.21 mPa/√
Hz
measured at the resonant frequency. The sensor exhibits a maximum signal-to-noise ratio (SNR) of 70 dB at the resonance frequency. Numerical analysis and simulations are also performed to substantiate the experimental demonstrations. The proposed sensing system is developed using a conventional drop-casting method. Consequently, the sensor is recognized as advantageous over the previous reports in terms of sensitivity, MDP, SNR, and fabrication feasibility.
