Papers by Author: Yong Hong

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Authors: Yong Hong, Seung Ho Hwang, Gao Ping Wang, Dong Pyo Hong
Abstract: This paper presents a primary study for a method of measurement using PZT sensors which is widely used for SHM. PZT sensor has many advantages when using smart material. It is easy to be shaped to various forms and can be embedded on the materials more conveniently. The development for a practical and quantitative technique for assessment of the structural health condition by PZT sensor associated with wave propagation is investigated. Two aluminum specimens bonded with PZT sensors tested for estimating characteristics of the wave propagate on specimens change by various damage condition cf. line crack, bolt loosening. To estimate condition of the specimens numerically, we suggest impedance and guided wave method in this paper.
Authors: Yong Hong, Byung Jin Kim, Dong Pyo Hong, Young Moon Kim
Abstract: Beam structures are a common form in many large structures, and therefore the real-time condition monitoring and active control of beams will improve the reliability and safety of many structures. However, the incipient damage, i.e. cracks, is not easy to be detected with using the traditional methods, such as modal analysis, etc. Piezoceramic (PZT) sensors offer special opportunities for the health monitoring of structures constructed by beams. The change of mechanical impedance of structures along with the occurrence of damage is sensitively indicated by the change of electro-impedance of PZT sensors. This paper presents work done on developing and utilizing PZT sensors to detect and quantitatively assess the extent and locations of cracks occurred in simulated structures. The PZT sensors are conducted particularly to generate the longitudinal wave along the beam specimen, and systematic experiments conducted on statistical samples of incrementally damaged specimens were used to fully understand the method, the cracks with different length and location are simulated to indicate the feasibility of the detection and assessment. To estimate the damage conditions numerically, in this paper, we propose the evaluation method of impedance peak frequency shift F and CC (Correlation Coefficient), Cov (Covariance). The results of experiments verify that the impedance peak frequency shift Δ F uniformly assesses the location of cracks, and as well CC. and Cov assesses the size of cracks efficiently. The study presents the method that is satisfied for much higher frequencies, alternate power, and minute damages.
Authors: Gao Ping Wang, Yong Hong, Byeong Hee Han, Dong Pyo Hong, Young Moon Kim
Abstract: The use of multi-type joints, such as rivet joints, adhesive joints, lap joints, L-shape joints, etc., has been driven by the need for stronger and lighter structures, particularly in bridges, aerospace structures, pipeline systems, automobiles industry. Among the multi-type joints, lap joints and L-shape joints possess a considerably important position. Moreover, in many real-field situations, it is not accessible to such joints, and thus it gives additional difficulties to detect damages. Fortunately, the electro-impedance method based on the use of smart sensors provides special opportunities for damage detection of such joints, which are not easy or impossible to be accessible. The piezoelectric-ceramic sensors which simultaneously act as an actuator and sensor are widely used for structural health monitoring. In the high frequency range, the electro-impedance-based technique using a piezoelectric-ceramic patch is very sensitive for the evaluation of the incipient and small damages. A large amount of experiments were executed and several conditions were imposed to simulate real-time damage, such as the bolt loosening and bolt absence. The different indices are discussed and executed to efficiently quantify the damage conditions. The theory behind this technique and the experimental investigations are presented in this paper. The analytical results strongly show the detectability and reliability of this method.
Authors: Yong Hong, Gao Ping Wang, Seung Ho Hwang, Hyun Sik Kim, Dong Pyo Hong
Abstract: A piezoelectric ultrasonic sensing system based on an optical fiber has been developed for detection of various damages. The ultrasonic wave generated from a piezoelectric actuator is guided and propagated in the optical fiber and then sensed by a piezoelectric sensor located at the other end of the fiber. The sensed signal can be influenced by environmental and physical changes around the optical fiber. In this study, the sensitivity of the optical fiber sensor is experimentally studied. Various patterns of damage, such as cracks, loosen bolts, holes, are more common forms in real structures. In particular, detection method of the damage with respect to various depths of the crack is presented in this paper.
Authors: Yong Hong, Gao Ping Wang, Byeong Hee Han, Dong Pyo Hong, Young Moon Kim
Abstract: Beam structures are a common form in many large structures, and therefore the real-time condition monitoring and active control of beams will improve the reliability and safety of many structures. This paper presents a damage assessment method which combines the impedance method and guided wave method. The combination enabled to improve the damage detection efficiency. The impedance method is used first to detect whether the damage occurs or not and judge the damage extent. The guided wave then is introduced to accurately localize damages. The improved method provides possibility for more accurately identifying and localization damages compared to that conventional method. A powerful wavelet transform is used to extract the signals efficiently. Additionally, with using the general function generator to excite the piezoceramic (PZT) patches to generate the guided wave, the guided wave propagates along with the beam structures with PZT patches bonded, and the real-time signals are recorded. Damages are indicated by a change of response signals when compared with a template undamaged condition. The wave attenuation and mode conversion is sufficient to detect various types of defects. The results show considerable ability for identifying and localization of the simulated damages.
Authors: Gao Ping Wang, Yong Hong, Jae Jung Lee, Dong Pyo Hong, Young Moon Kim, Jae Yeol Kim
Abstract: We present a study on the development of a practical and quantitative technique for the assessment of the structural health condition with using piezoceramic (PZT) sensors. The electroimpedance- based technique with the PZT patches is very sensitive for evaluation of the incipient and small damage in a high frequency range, and however the commonly traditional modal analysis method is effective only for considerably larger damages in low frequency range. The paper presents the performance of the performance of the electro-impedance-based technique in detecting and characterizing real-time damage on the specimen that is an aluminum plate fastened with bolts and nuts by different torques. By using the special arrangement of the PZT sensors, the required longitudinal wave is generated through the specimen. A large number of experiments are conducted and the different conditions of the specimen, i.e. the location of loosening bolts and the loosening extent of bolts are simulated, respectively. Since fixing and loosening the loosened bolt is controlled by a torque wrench, we can control exactly the experiment of the different torques. Compared with the simulated healthy condition, we can find whether or not there is a damage in the specimen with using an impedance analyzer with the PZT sensors. Several indices are discussed and used for assessing the different simulated damages. As for the location of bolt loosening, the RMSD is found to be the most appropriate index for numerical assessment and as well the RMSD shows strongly linear relationship for assessing the extent of the bolt loosening. The possibility of repeatability of the pristine condition signatures is also presented and the appropriate frequency range and interval are uniquely selected through large numbers of experiments. The analytical results strongly show the sensibility and reliability of the electro-impedance based technique.
Authors: Yong Hong, Byeong Hee Han, Dong Pyo Hong, Sung Mo Yang, Young Moon Kim, Kyeong Suk Kim
Abstract: This paper describes a primary study for a new method of enhancing measurement with using an impedance analysis method that is applied to structural health monitoring. The goal of this research is to show basic information that is used to evaluate the structural health condition with using piezoelectric sensors. We present a study for the development of a practical and quantitative technique for the assessment of the structural health condition with using a piezoelectric impedance-based technique that is associated with longitudinal wave propagation. The natural frequency has a tendency of frequency shifting with respect to the hole size that corresponds to the real structure’s crack size. To numerically estimate the damage condition, we suggest the Cov (Covariance) and CC (Correlation Coefficient) evaluation methods.
Authors: Yong Hong, Su Hyun Han, Jae Jung Lee, Dong Pyo Hong, Young Moon Kim
Abstract: In the study, the development of aerial platform truck of 42m boom system has been completed to be satisfied with working in much higher place. To avoid the rollover accident of vehicles while working, 3D FEA is applied to verify the 3D design, stress concentration, stress distribution, deflection, natural frequencies etc. In these analyses, traction load of Boom System, 700 Kg and traction degree analyzed to 0° ~ 85°. Analysis result, when Boom System's angle is 0°, could know that stress concentration and deflection are obtained to maximum. We could predict that maximum point of Stress concentration is 3.275 as safety factor and deflection of Boom system end part is max. 78.5Cm. Also could know that natural frequency and mode shape of boom system are stable in correlation with aerial platform truck's operation area. With these results, the structural stability of boom system in 42m aerial platform truck is obtained, then finally trying to find an optimum design of aerial platform truck.
Authors: Gao Ping Wang, Yong Hong, Dong Pyo Hong, Sung Mo Yang, Young Moon Kim
Abstract: Pieces of large-scale equipment such as a ball mill system are subjected to heavy and alternate loads under the worst working conditions, which result in higher fault rates. However, since such equipment exerts important functions to the economy and industry, it isn’t recommendable to halt production in order to detect the defects under unconfirmed faults. We explore a reliable and practical fault diagnosis scheme for the ball mill system that is widely used in the building material industry. With utilizing the signal acquisition and process system of vibration, the field testing and analysis are performed based on the violent vibration of an edge-transmission Φ3×11m ball mill system. The primary diagnosis that is based on the configuration of the transmission system and foundation stiffness is found, and a feasible resolution scheme is obtained, so that the optimal and economic reform scheme is determined. The detailed scheme has been adopted by the production industry. This study that is based on the fault diagnosis of the edgetransmission ball mill system has a comprehensive significance of theory and reality. This provides a larger basis for vibration inspection and fault diagnosis in building material industries.
Authors: Yong Hong, Gao Ping Wang, Yeon Gon Go, Dong Pyo Hong, Tae Jin Chung
Abstract: In this paper, a pendulum system is constructed to perform the fundamental research which is concentrated on the various frequency patterns of impact-object simulation tests. We confirmed the application possibility for the method of discriminable pattern recognition whether impact-object is human-like or not via frequency analysis using smart sensors. Therefore a specific experimental data are compared and analyzed with the obtained database within a short time period. The impact analysis system, which is based on the above processing, can be developed and then used to recognize the impact information measured by smart sensors.
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