• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.1
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• pp.64-71
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• 2009

In this paper, a study on low-velocity impact response of honeycomb sandwich panels was done for the changes of impact location and core fabrication angles. The test specimens were made of glass/epoxy laminate facesheet and aluminum honeycomb core. Square samples of 100mm and 100mm sides were subjected under low-velocity impact loading using instrumented testing machine at three energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for the changes of impact location and core fabrication angle. The impact damage size were measured at facesheet surface by 3-Dimensional scanner. Also, sandwich specimens after impact test were cut to analyse the failure mode.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.295-300
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• 1998

In this paper, a real time diagnostic algorithm fur estimating the impact location by loose parts is proposed. It is composed of two modules such as the alarm discrimination module (ADM) and the impact-location estimation module(IEM). ADM decides whether the detected signal that triggers the alarm is the impact signal by loose parts or the noise signal. When the decision from ADM is concluded as the impact signal, the beginning time of burst-type signal, which the impact signal has usually such a form in time domain, provides the necessary data fur IEM. IEM by use of the arrival time method estimates the impact location of loose parts. The overall results of the estimated impact location are displayed on a computer monitor by the graphical mode and numerical data composed of the impact point, and thereby a plant operator can recognize easily the status of the impact event. This algorithm can perform the diagnosis process automatically and hence the operator's burden and the possible operator's error due to lack of expert knowledge of impact signals can be reduced remarkably. In order to validate the application of this method, the test experiment with a mock-up (flat board and reactor) system is performed. The experimental results show the efficiency of this algorithm even under high level noise and potential application to Loose Part Monitoring System (LPMS) for improving diagnosis capability in nuclear power plants.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.101-108
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• 1999

In this paper, a real time diagnostic algorithm for estimating the impact location by loose parts is proposed. It is composed of two modules such as the alarm discrimination module (ADM) and the impact-location estimation module(IEM). First, ADM decides whether the detected signal that triggers the alarm is the impact signal by loose parts or the noise signal. Second, IEM by use of the arrival time method estimates the impact location of loose parts. In order to validate the application of this method, the test experiment with a mock-up (flat board and reactor) system is performed. The experimental results show the efficiency of this algorithm even under high level noise and potential application to Loose Part Monitoring System (LPMS) for improving diagnosis capability in nuclear power plants.

• Smart Structures and Systems
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• v.23 no.2
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• pp.123-139
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• 2019

Impact forces induced by external object collisions can cause serious damages to civil engineering structures. While accurate and prompt identification of such impact forces is a critical task in structural health monitoring, it is not readily feasible for civil structures because the force measurement is extremely challenging and the force location is unpredictable for full-scale field structures. This study proposes a novel approach for identification of impact force including its location and time history using a small number of multi-metric observations. The method combines an augmented Kalman filter (AKF) and Genetic algorithm for accurate identification of impact force. The location of impact force is statistically determined in the way to minimize the AKF response estimate error at measured locations and then time history of the impact force is accurately constructed by optimizing the error co-variances of AKF using Genetic algorithm. The efficacy of proposed approach is numerically demonstrated using a truss and a plate model considering the presence of modelling error and measurement noises.

• Journal of Digital Contents Society
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• v.18 no.3
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• pp.567-575
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• 2017

Location-based services play an important role in many applications such as disaster warning systems and recommendation systems. These applications often require not only location information (e.g., name, latitude, longitude, etc.) but also the impact of events (e.g., earthquake, typhoon, etc.) on locations. Recently, to provide the impact of an event on a location, how to calculate location trustiness by using multimodal information such as earthquake information and disaster sensor data is researched. In the previous approach, the linear decrement of impact value of an event is applied to obtain the location trustiness of a specific location. In this paper, we propose a new approach to enrich location trustiness, that is, the impact of an event on a location, by using social media information additionally. Firstly, we design a collecting system for earthquake information and social media data. Secondly, we present an approach of location trustiness calculation based on earthquake information. Finally, we propose a new approach to enrich location trustiness by augmenting the trustiness in spatially distributed manner based on social media.

• Smart Structures and Systems
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• v.6 no.2
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• pp.147-165
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• 2010

Impact damage detection in composite structures has gained a considerable interest in many engineering areas. The capability to detect damage at the early stages reduces any risk of catastrophic failure. This paper compares two advanced signal processing methods for impact location in composite aircraft structures. The first method is based on a modified triangulation procedure and Genetic Algorithms whereas the second technique applies Artificial Neural Networks. A series of impacts is performed experimentally on a composite aircraft wing-box structure instrumented with low-profile, bonded piezoceramic sensors. The strain data are used for learning in the Neural Network approach. The triangulation procedure utilises the same data to establish impact velocities for various angles of strain wave propagation. The study demonstrates that both approaches are capable of good impact location estimates in this complex structure.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.1
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• pp.1-7
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• 2011

In the bomb impact test, to acquire the bomb impact point location the high-priced embedded equipments such as the Bomb Scoring System or the EOTS are needed. Recently, a high-resolution image processing could be possible since the resolution of the commercial camera is growing rapidly. In this paper we first propose an image transformation method for acquiring the real bomb impact image using a high-resolution commercial camera, and then present the process calculating the real bomb impact point location coordinate from the transformed image. Based on the experimental results we found the possibilities that the real bomb impact point information could be effectively earned just using the commercial camera.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.706-711
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• 2007

Numerical studies were performed to examine the effects of notch location of impact specimens on the failure behavior of HAZ (heat affected zone) when Charpy V-notch impact test were made at a low temperature ($1^{\circ}C$). Carbon steel plate (SA-516 Gr. 70) with thickness of 25mm for pressure vessel was welded by SMAW (shielded metal-arc welding) and specimens were fabricated from the welded plate. Charpy tests were then performed with specimens having different notch positions of specimens varying from the fusion line through HAZ to base metal. A series of finite element analysis which simulates the Charpy test and crack propagation initiating at the tip of V-notch was carried out as well. The finite element analysis takes into account the irregular fusion line and non-homogenous material properties due to the notch location of the specimen in HAZ. Results reveals that the energies absorbed during impact test depend significantly on the notch location and direction of specimen. Finite element analysis also demonstrates that the notch location of specimens, to a great extent, influences the reliability and consistency of the test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1555-1565
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• 2010

This paper presents a new method for indentifying the location of impact source in a buried duct. In a gas pipeline, the problem of leakage occurs due to the mechanical load exerted by construction equipment. Such leakage can cause catastrophic disasters in gas supply industries. Generally, the cross-correlation method has been used for indentifying the location of impact source in a pipeline. Since this method involves the use of the dispersive acoustic wave, it derives an amount of error in process of estimating the time delay between acoustic sensors. The object of this paper is to estimate the time delay in the arrival of the direct wave by using the wavelet transform instead of the dispersive wave. The wavelet transform based method gives more accurate estimates of the impact location than the cross-correlation method does. This method is successfully used to identify the location of impact force in an actual buried gas duct.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.609-615
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• 2016

Measuring similarity between two signals is a key element of the location template matching (LTM) method which is one of impact source localization technique. As a measure of similarity, the correlation coefficient is most widely used, and the group delay based method is recently proposed to improve the accuracy of finding the impact source. In practice, the LTM method assumes that the similarity between two signals decreases as the distance between two corresponding impact points increases, where the distance between two neighboring impact points defines the grid spacing. In this paper, it is shown that this assumption is not always true but the correlation coefficients fluctuate forming a main robe and many side robes as the distance between two neighboring impact points increases. On the other hand, the standard deviation of group delay sharply increases with a small increase of the grid spacing. These are demonstrated by using a simple cantilever beam. Based on these findings, an optimal way of implementing the LTM method may be suggested by combining the correlation coefficient and the group delay based approaches.