• Geomechanics and Engineering
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• 제9권2호
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• pp.207-218
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• 2015

In this paper, forming of fully clamped circular plate by using low velocity impact system has been investigated. This system consists of liquid shock tube and gravity drop hammer. A series of test on mild steel and aluminum alloy plates has been done. The effect of varying both impact load and the plate material on the deflection are described. This paper also presents a simple model to prediction of mid-point deflection of circular plate by using input-output experimental data. In this way, singular value decomposition (SVD) method is used in conjunction with dimensionless number incorporated in such complex process. The results of obtained model have very good agreement with experimental data and it provides a way of studying and understanding the plastic deformation of impact loads.

• 한국해양공학회지
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• 제26권6호
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• pp.33-38
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• 2012

In our study, a closed-type penetration unit for standard penetration test (SPT) equipment was developed in order to operate in an underwater environment. This type causes energy dissipation, mainly due to the small gap between an airtight case and moving hammer. The dissipation was estimated through a CFD analysis. The computed dissipated energy was less than 1.2% compared to the potential energy of the hammer with the given gap. Subsequently, the impact energy of the underwater SPT equipment was within 1.2% of that for the SPT equipment on land.

• 센서학회지
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• 제28권6호
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• pp.371-376
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• 2019

We have developed an acoustic resonance inspection system to inspect the welding defects in the mechanical parts fabricated using friction stir welding method. The inspection system was consisted of a DAQ board, a microphone sensor, an impact hammer, and controlled by a PC software. The system was developed to collect and analyze the sound signal generated by hitting the sample with an impact hammer to determine whether it is defective. In this study, 100% welded good samples were compared with 95%, 90%, and 85% welded samples, respectively. The variation of the completeness in welding did not affect the visual appearance in the samples. As a result of analyzing the natural frequencies of the good samples, the five natural frequency peaks were identified. In the case of the defective samples, the frequency change was observed. The welding failure detection time was fast enough to be only 0.7 seconds. Employing our welding defect inspection system to the actual industrial field will maximize the efficiency of quality inspection and thus improve the productivity.

• 한국정밀공학회지
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• 제33권5호
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• pp.401-407
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• 2016

This paper describes the derivation methodology of the working torque predictive model that can be used in the initial design stages of the impact hammer tool. The working torque control mechanism is designed, taking into account various factors, such as the force of the spring and friction. Firstly, the analysis dynamic model for working environments was modeled as an additional bush and spring, and verified by comparing the test results of the working torque. Secondly, the main performance parameters of the working torque were theoretically defined by analyzing the operating mechanism. The equation to predict the working torque was derived using the dynamic analysis results according to the value changes of the parameters. The prediction equation of the working torque was validated by comparing the predicted results with the experimental data. The error difference between the experimental data and the predictive model results was found to be 8.62%.

• Computers and Concrete
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• 제28권5호
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• pp.479-486
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• 2021

Reinforced concrete (RC) slabs are exposed to several static and dynamic effects during their period of service. Accordingly, there are many studies focused on the behavior of RC slabs under these effects in the literature. However, impact loading which can be more effective than other loads is not considered in the design phase of RC slabs. This study aims to investigate the dynamic behavior of two-way RC slabs under sudden impact loading. For this purpose, 3 different simply supported slab specimens are manufactured. These specimens are tested under impact loading by using the drop test setup and necessary measurement devices such as accelerometers, dynamic load cell, LVDT and data-logger. Mass and drop height of the hammer are taken constant during experimental study. It is seen that rigidity of the specimens effect experimental results. While acceleration values increase, displacement values decrease as the sizes of the specimens have bigger values. In the numerical part of the study, artificial neural networks (ANN) analysis is utilized. ANN analysis is used to model different physical dynamic processes depending upon the experimental variables. Maximum acceleration and displacement values are predicted by ANN analysis. Experimental and numerical values are compared and it is found out that proposed ANN model has yielded consistent results in the estimation of experimental values of the test specimens.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.885-890
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• 2007

Fast Fourier Transformation(FFT) is one of the most useful way to analyze response signal for the purpose of grasping the dynamic characteristics of system. Vibration test using impact hammer is typical and simple experimental method widely used for catching hold of dynamic peculiar characters and modal behaviors of system. In this thesis, impact testing module for NI-PXI equipment is developed. The analyzing and visualizing module are developed with LabVIEW tool. A user can see quickly and easily modal shape of system after analyzing acquired data. This developed module will be expected to build up more convenient and serviceable measurement system.

• 한국생산제조학회지
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• 제9권3호
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• pp.76-82
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• 2000

It is well known that during the oxygen cutting process residual thermal stresses are produced in weldment. The local non-uniform heating and subsequent cooling which takes place during any welding process causes complex thermal strains and stresses to finally lead to residual stresses exceed to the yield stress. High tensile stresses combined with applied structural load in the region near the welded joint can given rise to distortion brittle fracture change of the fatigue strength and stress corrosion cracking. The appropriate treatment of the welded component which reduces the peak of he welding residual stresses is believed to lower risk of the fracture during the service of the structure. In this study the impact loading in oxygen cutting frame was applied to reduce the residual stress. After applying the impact loading redistribution of resid-ual stress was measured by cutting method and the effect of fatigue was tested.

• 한국항공우주학회지
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• 제38권1호
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• pp.22-28
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• 2010

복합재 구조물의 손상을 탐지하기위해 비파괴 검사법이 폭넓게 사용되고 있다. 태핑시험은 복합적층판의 손상을 탐지하는데 가장 일반적으로 사용하는 방법이다. 이 방법은 가벼운 해머 같은 장치를 이용하여 검사부위를 두드리고, 국부적인 강성변화를 이용하여 구조물의 손상을 평가한다. 진동신호의 변화는 동적인 접촉하중을 측정하여 탐지할 수 있다. 본 연구에서는 구조물에 층간분리나 표면균열 등의 손상이 존재하는 경우 태핑 시 충격하중이력의 특성이 변하는 것을 보였다. 그리고 손상의 영향을 검토하기위해 균열이 있는 복합재 로터블레이드에 대한 충격해석을 수행하였다.

• Computers and Concrete
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• 제30권1호
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• pp.19-32
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• 2022

This paper presents an investigation into the failure of RC columns under impact loadings. A numerical simulation of 19 identical RC columns subjected to single and repeated impact loadings was performed. A free-falling hammer was dropped at midspan with the same total kinetic energy input but varying mass and momentum. The specimens under the repeated impact test were struck two times at the same location. The colliding index, defined as the impact energy-momentum ratio, was proposed to explain the different impact responses under equal-energy impacts. The increase of colliding index from low to high indicates the transition of the impact response from static to dynamic and failure mode from flexure to shear. This phenomenon was more evident when the column had a greater axial load and was impacted with a high colliding index. The existence of the axial load had an inhibitory effect on the crack development and increased the shear resistance. The second impact changes the failure mode from flexural to brittle shear as found in the specimen with 20% axial load subjected to high a colliding index. Moreover, a deflection prediction equation based on the impact energy and force was limited to the low colliding index impact.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 2호
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• pp.103-106
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• 1998

본 논문은 상용 FEM-BEM 프로그램을 사용하여 점-조화 가진(harmonic point excitation)에 의한 자유지지 경계 조건을 갖는 원통 셸(cylindrical shell)의 방사 효율(radiation efficiency) 실험의 결과와 비교하였다. 우선 충격 해머 실험(impact hammer test)을 통한 모드 시험(modal testing)으로 원통 셸의 공진 주파수(natural frequency)와 모드 형상(mode shape)의 특징을 살펴보고 다음으로 점-조화 가진에 의한 원통 셸의 방사 효율을 SYSNOISE와 ANSYS로 해석해 보았다. 동시에 음향 세기 실험을 통한 방사 효율을 측정하여 전산 해석의 결과와 실험의 결과를 비교해 보았다.