Multi-Functional Materials and Structures III

Volumes 123-125

doi: 10.4028/

Paper Title Page

Authors: Yong Ha Yang, Seung Hyun Choi, Jae Yeol Kim, Yong Hoon Cha
Abstract: Vibrations during lathe machining include vibrations by a sudden clash of a tool against a workpiece as an external excitation, vibrations by irregular tissues of the workpiece, vibrations by regular excitation due to asymmetric torque, and vibrations by bearing defects. Furthermore, machine tools are heated because most of the supplied energy is transformed to heat and becomes the heat source of the machine tool or an internal heat source. In addition, the spindle is one of the largest internal heat sources. The heat distortion of the spindle by this heat source has the most serious effect on the total heat distortion of the machine tool, and the heat distortion of machine tools is the largest cause of the degradation of cutting precision. In order to obtain accurate data about the causes of such vibrations and heat, this study measured the vibrations and thermal changes of each specimen using a vibrometer and an infrared thermography camera.
Authors: Seung Hyun Choi, Lee Ku Kwac, Jae Yeol Kim
Abstract: The infrared thermography technique is being applied in many areas. Particularly these days, non-destructive inspection and evaluation using the ultrasound-infrared thermography technique are hogging the spotlight in a wide range of study areas. The ultrasound-infrared thermography technique uses the principle that ultrasound waves projected to objects with cracks or defects at connections generate local heat from the defective surface. In this research, introduce nondestructive evaluation method for total inspection of special shoes applying Ultrasound Infrared thermography Technique. Performance of the proposed method are shown by through thermo-Image. The total inspection system using infrared thermal camera for special shoes, its applicability, and system configuration are introduced.
Authors: Kyung Seok Song, Sun Young Na, Jae Yeol Kim
Abstract: The NAUT technique allows non-contact ultrasonic testing in air. If the NAUT technique can be applied, not only ultrasonic testing in air with no couplant would be possible, but also the stable transmission and reception of ultrasonic waves, which would thus enable ultrasonic testing of hot or cold materials, or rough surfaces of specimens that could not be tested with conventional-contact ultrasonic testing techniques. By trying NAUT for CFRP (carbon fiber-reinforced plastic) specimens, the applicability of NAUT in these areas was observed, and the results from the waveforms of parts of the specimens were analyzed. To verify the usefulness of NAUT, first, artificially defective specimens were tested to investigate the defect detection ability of NAUT; and second, a test was conducted to select the test conditions, the ultrasonic propagation characteristics, and the mode conversion by the material thickness. Both the spot welding and CFRP specimens showed good applicability of NAUT. For the spot welding specimen, the ultrasonic transmittance was highest at the spot-welded part, regardless of the thickness and location of the specimen. For the CFRP specimen, the waveforms of a defective part and a defect-free part were compared, and the existence of delamination was discovered through the increase and decrease in the amplitude. These findings confirmed the practicality (usefulness) of NAUT.
Authors: Shun Bo Zhao, Ji Hao Chen, Ji Tao Yao, Song Wei Pei
Abstract: Normally, the structural fundamental frequency can be got from the vibration tests by means of accelerometers or velocimeters linked with the dynamic signal measuring and analysis system. Based on the principle of reinforcement strain variation synchronized with the structural vibration, the paper introduces a new method to obtain the fundamental frequency of bridge by measuring the environmental dynamic strains of resistance strain gauges bonded on the reinforcing bars of bridge hinge and deck pavement. The real-time strain signals caused by vehicles passed on the bridge were recorded by the dynamic signal measuring and analysis system, and transformed into strain spectrum by fast Fourier transformation in which the fundamental frequency was got. The result was the same as that of velocimeter measuring. Therefore, the bridge fundamental frequency can be simply and accurately measured by the resistance strain gauges.
Authors: Y. Shinyama, Yoshimi Hatsukade, Saburo Tanaka, Y. Takai, M.S. Aly-Hassan, Asami Nakai, Hiroyuki Hamada
Abstract: Braided carbon fiber reinforced plastics (CFRP) is one of the multifunctional materials for applications to industrial products. We applied the superconducting quantum interference devise (SQUID) nondestructive evaluation (NDE) technique with high magnetic sensitivity and spatial resolution to inspect the state of the fabric in the braided CFRP. We prepared flat braided CFRP samples with nonuniform, uniform and cut-out bundles, which were fabricated with fold biaxial (±45º) tubular fabric and epoxy resin. While injecting ac current into each sample, the diagonal magnetic field gradients dBz/dx and dBz/dy above each sample were measured by the NDE system employing a SQUID gradiometer and xy-scanning stage, and then, the current flow in each sample was visualized by the field-gradient-to-current conversion method. In the measurements, it was shown that the current flowed along the continuous bundles in the cases of nonuniform and uniform samples, and it transmitted between bundles in the case of the sample with cut-out bundles. From these results, we showed the possibility that the NDE method can be applied to the nondestructive inspection of the integrity of the textile of braided CFRP.
Authors: Je Woong Park, Kwang Hee Im, David K. Hsu, Chien Ping Chiou, Daniel J. Barnard
Abstract: Recently, terahertz ray imaging has emerged as one of the most promising new powerful nondestructive evaluation (NDE) techniques, and new application systems are under processing development for the area applications. In this study, a new time-domain spectroscopy system was utilized for detecting and evaluating layup effect and flaw in FRP composite laminates. Extensive experimental measurements in reflection mode were made to map out the T-ray images. Especially in this characterization procedure, we estimated the electromagnetic properties such as the refractive index. Estimates of properties are in good agreement with known data. Furthermore layup effect and flaw of FRP composite laminates were observed in reflection mode and limitations will be discussed in the T-ray processing.
Authors: Shun Bo Zhao, Shan Zhao, Su Yang, Xiao Lu Ma
Abstract: To improve the durability of external thermal insulation plate on walls, the new reinforced concrete composite wall(RCCW) with inner insulating layer of polystyrene panel was developed. The paper introduces the thermal insulation tests of the RCCWs by the protection chest method, and studies the method for eliminating the effect of heat-bridge on the test results of conduct heat coefficient of the RCCW. The results show that the test value of conduct heat coefficient of the RCCW was obviously affected by the heat-bridge in specimen caused by the connected concrete such as support and concrete cover around the polystyrene panel, the practical value can be obtained by mean of taking off the percent of heat-bridge effect.
Authors: Jung Ryul Lee, Hye Jin Shin, Chen Ciang Chia, Hyo Mi Jeong, Dong Jin Yoon
Abstract: Soundness of wind turbine blade plays paramount role in supplying cheap and reliable wind energy. To ensure that blades are sound and free from inherent manufacturing defects, easy and reliable quality evaluation before delivering blades for installation is crucial. We propose an ultrasonic amplitude imaging method based on Ultrasonic Propagation Imaging (UPI) system for this purpose. The system utilizes a scanning Q-switched continuous wave laser as ultrasonic wave generator. Various acousto-ultrasonic sensors, either contact or non-contact type, could be adopted as ultrasonic receiver. The system was tested on a blade section made of glass fiber reinforced plastic sandwiched with balsa wood. The leading edge of the specimen with a kissing disbond was inspected. A PZT-based sensor attached temporarily on the outer surface of a blade was used for ultrasonic reception to demonstrate that this imaging method is applicable even for the blades without integrated sensor. The amplitude map clearly showed the disbond defect with the kissing features. The location, shape, and size of the defect evaluated from the result agree excellently with the actual defect. The result proved that the proposed method works well for the quality evaluation of wind turbine blades. Inheriting the advantages of UPI technology, i.e. focusing-free characteristics, acceptance of large laser incident angle up to 60°, and rapid scanning without needing an expensive scan gantry, this system is suitable for automatic quality evaluation of blades with different geometry. On top of that, this system does not require any reference data, making it a flexible quality evaluation system suitable for different methods of blade production flow.
Authors: Feng Xian Qiu, Dong Ya Yang, Qing Zhang, Guo Rong Cao
Abstract: A novel azobenzene polyelectrolyte (ABAPE) was synthesized based on chromophore 4-(4’-nitrophenylazo) naphthol (NPAN), epoxychloropropane and α-methacrylic acid. The ABAPE was characterized by FT-IR and UV-vis spectroscopy. The aggregation behaviors of ABAPE were investigated based on different pH values by the UV-vis spectroscopy. The isomerization behavior of the ABAPE in DMAC solution was studied by 256 nm UV irradiation light. Attenuated total reflection (ATR) method was adopted and carried out the measurement of refractive index of the thin film. The thermo-optic coefficient (dn/dT) was -2.9228×10-4°C-1 and was bigger than inorganic materials such as silica glass, zinc silicate glass, borosilicate glass and the organic materials of polystyrene and PMMA. These results showed that the polyelectrolyte could be used to carry out optical storage and thermo-optic switch.
Authors: Jung Ryul Lee, Chang Yong Yoon, Dipesh Dhital, Dong Jin Yoon
Abstract: The leakage of toxic or flammable chemical substances that might affect or endanger public safety has always attracted the attention of the researchers to develop a chemical sensor that could prevent any life-threatening incidents. Due to its robust features, hard polymer clad fiber (HPCF) was used in this experiment to develop an all-fiber optical chemical sensor. The outer hard polymer clad was removed by using mechanical method to expose the inner core. The exposure lets contact between the leaked chemical and the core, both with different refractive indices (RI). The change in signal property of the passing light wave occurs at this point and hence can be detected using optical time-domain reflectometer (OTDR). In this way, HPCF was transformed into a fiber optic chemical sensor. OTDR was used as a sensing system that allowed the sensor to detect and localize the leakage of chemical substances in real-time, by measuring the light loss in backscattering light (signal) that was caused due to extraction of chemical on fiber cladding. This light loss is based on leaky wave mode principle. The reliability of the sensor was tested with Benzene, Toluene, Pyridine, Dimethylsulphoxide and several other toxic chemicals. The results showed that the sensor was able to detect the chemicals (in liquid state) and localize the event positioning. With the promising results, the sensor will be further tested with different types of chemicals to optimize the fiber chemical sensing system.

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