Papers by Keyword: Piezoelectric Sensor

Abstract: Nano Composites Polymer represents a class of multifunctional sensors that can effectively respond to changes in electrical properties when subjected to external forces acting on their physical characteristics. The research aims to develop nanocomposite polymer sensors that can respond well and be easily molded. The experimental process involved mixing Ultra-high-molecular-weight polyethylene (UHMWPE) with 1%, 4%, and 7wt% of carbon nanotubes (CNT) using the hot pressing method, leading to remarkable improvements in the electrical and mechanical properties of the composite polymers. The distribution patterns of CNT at different weight ratios showed that 4 wt% exhibited a more desirable and uniform distribution. However, at 1 wt%, the amount of CNT was insufficient, resulting in scattering and disconnection. On the other hand, at 7 wt%, the CNT distribution appeared to be densely bundled in some areas, leading to detrimental effects on the mechanical and electrical properties, as well as the electrical percolation threshold of the composites. Regarding the mechanical properties test, significant improvements were found at 4 wt% for the tensile strength, but when the filler content exceeded 4 wt%, there was a reduction in the tensile strength of the CNT/UHMWPE composites. Additionally, the change in electrical resistance based on the physical characteristics was examined by varying the percentage of CNT added to UHMWPE through compression and bending tests. The compression tests were conducted using weights ranging from 0 to 10 kg, and the bending tests were performed with angles from 0° to 40° degrees. In terms of the test results, however, with 4% and 7% wt% CNT filler, the electrical resistance values could be successfully measured by a multimeter. The electrical percolation threshold was found to be very good at 4 wt%. For the compression testing results, the resistance values ranged from approximately 27.329 to 32.389 KΩ for the 4 wt% filler and from 0.504 to 0.552 KΩ for the 7 wt% filler. As for the bending testing, the resistance values ranged from approximately 4.019 to 4.044 KΩ for the 4 wt% filler and from 0.427 to 0.432 KΩ for the 7 wt% filler.

Abstract: This work is devoted to the investigation of the characteristics of acoustic emission waves to establish their relations with the parameters of the fracture of the structure of the material. The paper presents the results of the analysis of acoustic emission signals recorded during the propagation of ultrasonic waves in metal sheet materials using piezoelectric sensors. The specimen was a rectangular aluminum plate. The piezoelectric sensor recorded acoustic emission signals generated by the Hsu-Nielsen source. The piezoelectric sensor is located in the center of the aluminum plate. Then sources are generated with different hardness to model various kinds of cracks at each specific location. To determine the informative component of a useful acoustic emission signal, the Morlet wavelet transformation was used. When excited by a fracture pencils of different hardness, the magnitude of the wavelet differ in the energy and intensity of the spectrogram.

Abstract: Strain readings recorded by surface mounted piezoelectric sensors due to impact events on composite panel are used to detect and characterize the impact. Sensor signals on a composite stiffened panels have been simulated by a valid numerical model. Applicability of least square support vector machines (LSSVM) on creating a meta-model to detect and characterize impact event has been investigated. In particular, the main advantage of LSSVM over other meta-modeling technique was found to be the smaller number of training data that is required. Experimental results on a composite panel has been used to validate the findings.

Abstract: In future, demand on portable electronic devices will create the requirements of enduring recharged sources of power. A non-environmental friendly conventional battery with limited lifetimes has no longer feasible option. One of the mostly used solution is the piezoelectric composite structure with sensing and also actuating capabilities, mainly as a MEMS device. The optimum between actuating and energy harvesting functions is difficult to obtain. The article is presenting a study regarding the posibility to optimize both functions, performed using an analytical model and also by simulation using a FEA model.

Abstract: Dynamic response of civil engineering structures was monitored in the paper, on basis of the excellent properties of piezoelectric smart sensor. There were two experiments: One was to study the relationship between the loading frequency and the piezoelectric sensor output by concrete block cyclic loading test; the other was to study the relationship between the sensor output and the stress amplitude by steel cantilever beam dynamic test. The results show that piezoelectric sensors have a good linear output performance.

Abstract: The partial discharge (PD) phenomenon is very harmful for electrical appliances and its early detection could be a cost effective approach for the industry. Although many techniques are used for PD detection yet no technique has presented widely acceptable solution. Still the subject needs parallel study of the detection techniques. In this study, partial discharge signal has been captured by the three techniques using fiber optic sensor (FOS), Piezoelectric Sensor (PZT), leakage current (LC) techniques. In these experiments, FOS shows good sensitivity in the range of applied high voltage > 5 kV. The sensitivity and noise level of PD signal was different in these two experiments. The location of a PD was demonstrated in a 500 gallon water tank using convolution method.

Abstract: A new type of upper and lower cover support structure piezoelectric sensor based on PVDF films is designed in terms of piezoelectric effect. Mechanics and mathematical models are established according to the structure of the sensor. The natural frequency of the sensor is derived finally. The natural frequency of the sensor is verified to meet the requirements of dynamic measurements by using theoretical calculations and simulations. The effectiveness of the calculating method is indicated.

Abstract: The partial discharge (PD) phenomenon is very harmful for electrical appliances and its early detection could be a cost effective approach for the industry. Although many techniques are used for PD detection yet no technique has presented widely acceptable solution. Still the subject needs parallel study of the detection techniques. In this study, partial discharge signal has been captured by the three techniques using fiber optic sensor (FOS), Piezoelectric Sensor (PZT), leakage current (LC) techniques. In these experiments, FOS shows good sensitivity in the range of applied high voltage > 5 kV. The sensitivity and noise level of PD signal was different in these two experiments.

Abstract: In reported research piezoelectric sensors were used for damage identicitaion purposes. Piezoelectric sensor was used for specimen excitation. Two techniques were investigated. The Electromechanical impedance (EMI) technique and guided wave based technique. The principle of EMI technique is based on measurement and analysis of impedance of piezoelectric transducers bonded on or embedded in investigated structure. It is assumed that structural change should influence the impedance characteristics of the transducers. The guided wave based technique is based on the guided elastic wave propagation phenomena. This type of waves can be used in order to obtain information about structure condition and possibly damaged areas. In reported investigation piezoelectric sensor was used to excite guided waves in chosen structural element. Dispersive nature of guided waves results in changes of velocity with the wave frequency, therefore a narrowband signal was used to minimize the dispersion phenomenon. The generated signal was amplified before applying it to the transducer in order to ensure measurable amplitude of excited guided wave. Measurement of the wave field was realized using laser scanning vibrometer that registered the velocity responses at a points belonging to a defined mesh. This non-contact tool allowed to investigate phenomena related to wave propagation. For both techniques numerical signals processing tools were developed. These numerical tools were designed to extract damage relevant features from EMI measurements and guided wave propagation measurements. The damage index (DI) was introduced on the basis of the extracted features.

Abstract: The paper consists of two parts. First, Electromechanical Impedance (EMI) method is proven to be able to determine some vibrational characteristics of the investigated structure. In order to verify this statement, Scannig Laser Vibrometry (SLV) is used to correlate frequency peaks of velocity (or displacement) operational deflection shapes with corresponding ones obtained by EMI method. Finally, the influence of moisture content in CFRP sample on resonance peaks is investigated using EMI method. Damage detection indicator in this case is based on shifts of resonant peaks.