Papers by Author: Shi Feng Huang

Abstract: It is vital to use acoustic emission technology to study on health monitoring of concrete. The aim of this study is to investigate the ability of the AE in order to test the effect of the stepwise displacement load on the damage mechanism of the concrete beams that embedded sensors under three-point bending. The result showed that as the damage increased, amplitude and energy increased. At the same time, embedded sensors can locate the position of the crack.

Abstract: 1-3 piezoelectric-damping composites were fabricated using piezoelectric ceramic as functional filler and epoxy resin as matrix by cut-filling method. The fabrication procedure of the composites was introduced. The effect of ceramic volume fraction on the damping behavior and the piezoelectric strain factor d₃₃ were studied. The results show that the damping property was firstly improved, and then decreased with the increase of the ceramic volume fraction. An optimal ceramic volume fraction of 15% was shown. TA increased from 29.78 to 32.34. The piezoelectric strain factor d₃₃ reached 323pC·N^-1.

Abstract: This paper described fabrication and comparison of embedded ultrasonic sensors for NDE applications. A 1-3 cement-based piezoelectric composite was used as the sensing element of the ultrasonic sensor. As a front matching layer between test material and piezoelectric materials, cement/epoxy resin was selected. In order to make the backing materials for sensors had enough acoustic attenuation performance, the backing material of sensors doped with tungsten powder. When the mass ratio of tungsten/cement backing was two and the thickness of cement/epoxy resin front-face matching was 3mm, the 1-3 cement-based piezoelectric ultrasonic sensor showed a significant enhancement in both relative pulse-echo sensitivity and-6dB bandwidth. These promising results suggested the great potential for developing high-performance ultrasonic sensors using the 1-3 cement-based piezoelectric composite.

Abstract: In order to increase the sensitivity, frequency bandwidth and longitudinal resolution of the 1-3 cement-based piezoelectric ultrasonic sensor, different metal powder/epoxy resin composite materials were used to make backing layer, and the performances of sensors were evaluated and compared. The results indicated that the increase of the sensitivity and the frequency bandwidth, as well as a decrease of the pulse wave number can be observed when the backing materials of metal powder/epoxy resin composite materials were added to the sensor. A 42%-increase of the maximum peak-to-peak value of the echo pulse response, a 52%-reduction of the ring down time and a 200%-increase of the bandwidth can be achieved by using the backing material.

Abstract: A new kind of embedded acoustic emission (AE) sensor has been developed and it was made up of 1-3 cement-based piezoelectric composites. Compared with those sensors which were traditionally affixed to concrete structures, the embedded AE sensors could minimize the leakage of AE hits and improve the accuracy of data acquisition. The AE thresholds of the sensors are 45dB and they can perceive the position of source and crack extending areas in concrete. Because of the low operation cost, the admirable compatibility with concrete and the excellent durability, the sensors could be widely used in the monitoring of civil structure.

Abstract: Strontium ferrite modified 0-3 cement-based piezoelectric composites were produced with piezoelectric ceramic [0.08Pb(Li1/4Nb3/4)O•0.47PbTiO3•0.45PbZrO3], sulphoaluminate cement and strontium ferrite by compressing technique, and the effects of poling conditions on the piezoelectric and dielectric properties were investigated. In order to contrast, a unmodified 0-3 cement-based piezoelectric composite was fabricated. The results show that the higher the poling electric field, the longer the poling time and the higher the poling temperature, the composites have the higher piezoelectric strain factor d33, piezoelectric voltage factor g33, dielectric constant εr and dielectric loss tanδ， and the strontium ferrite modified composites are polarized more easily, and have better properties than the unmodified composites. In the meantime, the optimum poling conditions were obtained, and the optimum poling field E, poling time t and poling temperature T were 5 kV/mm, 20 min and 80 °C.

Abstract: This study adopted home-made embedded piezoelectric transducers and external commercial ultrasonic transducers respectively to monitor early hydration processes of cement. This paper discussed the development of ultrasonic amplitude and frequency spectrum during the hydration process. It is proved that the method is effective for monitoring the hydration of cement paste. The embedded transducer could resolve the coupling problem of ultrasonic monitoring and it could be used for the whole life health monitoring of concrete.

Abstract: The piezoelectric ceramics Pb_0.94Sr_0.06(Zr_0.53Ti_0.47)O₃+(Ni₂O₃+Cr₂O₃)0.1wt% + x wt%MnO₂ + y wt%CeO₂ (abbreviated as PCrNi-4) were prepared by a traditional ceramics process in this paper. The influences of MnO₂ and CeO₂-doping and sintered temperature on matrix material properties were studied by orthogonal tests. The effects of different inducing factors on the microstructure and dielectric loss were analyzed by means of XRD, SEM and electric measurement. The results indicate that the optimum process conditions are w(MnO₂)= 0.1%, w(CeO₂)= 0.3% and the sintering temperature 1280°C. The property parameters of samples are: d₃₃=304.8pC/N, Kp=0.6113, ε^T₃₃=1520, tanδ=0.00289, d₃₃×g₃₃=61.12×10^-12CVm/N.

Abstract: 1-3 polymer-based piezoelectric composites were fabricated using epoxy as the matrix by the cut-filling method. The influences of PMN volume fraction on the piezoelectric and dielectric properties of the composite were analyzed, and then the piezoelectric composite was fabricated to transducer whose properties were also analyzed. The results indicate that with increasing the PMN volume fraction, both the hydrostatic piezoelectric voltage g_h and hydrostatic figures of merit d_h·g_h of the composite decrease, while the relative dielectric constant ε_r increases. The hydrostatic piezoelectric strain d_h has the optimum value in the PMN volume fraction range of 40%-60%. The resonant frequency of transducer in water is 306.5 kHz and anti-resonant frequency is 352.6 kHz.

Abstract: This study utilized embedded piezoelectric transducers for monitoring of cement hydration process. Longitudinal ultrasonic transducer which was suitable for being embedded in cement paste was prepared by cutting PZT rods and coating epoxy layer. The transducers were used to generate and receive ultrasonic waves to continuously observe the hydration of cement paste. The characteristics of wave parameters such as wave velocity, amplitude and frequency were used to interpret the hydration process of cement. Relationship between the character values of the wave and the process of hydration could be established. Therefore, it is feasible to observe the hydration progress using this technology. The coupling problem existed in traditional ultrasonic monitoring of hydration can be solved and the whole life monitoring of cement materials can be also achieved through this method.