• 한국소음진동공학회논문집
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• 제13권5호
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• pp.334-340
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• 2003

Exponential window function Is widely used In impact hammer testing to reduce leakage error as well as to get a good S/N ratio. The larger its decaying rate is, the more effectively the leakage errors are reduced. But if the decay rate of the exponential window is too large, the FRF is distorted. And the modal parameters of the system can not be exactly identified by modal analysis technique. Therefore, it is a difficult problem to determine proper decay rate in impact hammer testing. In this paper, amount of the FRF distortion caused by exponential window is theoretically uncovered. A new circle fitting method is also proposed so that the modal parameters are directly extracted from impulse response spectrum distorted by the exponential-windowed impulse response data. The results by the conventional and proposed circle fitting method are compared through a numerical example.

• 한국소음진동공학회논문집
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• 제12권10호
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• pp.792-798
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function (FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• 터널과지하공간
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• 제23권4호
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• pp.271-279
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• 2013

본 기술보고에서는 천공장비의 종류와 작동방식에 대해 간략히 소개하였다. 이 중 탑해머 방식의 천공기에 탑재되는 부품 및 세부 기술을 조사하였다. 탑해머 천공기술에 연관된 국내외 기술현황을 분석하고, 국내 기술수준과 선진기술 수준을 비교하였다. 이를 바탕으로 천공 관련 융복합 기술의 연구개발 필요성을 토의하고, 선진국과 기술격차를 줄이기 위한 천공산업의 미래 전략을 제안하였다.

• 대한물리의학회지
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• 제6권1호
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• pp.103-108
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• 2011

Purpose : The purposes of this study were to compare the muscle activity ratio of tibialis anterior (TA) / extensor digitorum longus (EDL) during the active ankle dorsiflexion in subjects with the normal toe (NT) and the hammer toe (HT). Methods : Nineteen subjects with the NT group and nineteen subjects with the HT group were recruited for this study. The muscle activities of TA and EDL were measured by using surface electromyography (EMG) and the angles of ankle dorsiflexion and eversion of the subtalar joint were measured by using 3-dementional motion analysis during the active ankle dorsiflexion in prone position. Results : The muscle activity ratio of TA / EDL was significantly lower in the HT group compared to the NT group (p<.05). The angle of ankle dorsiflexion was significantly lower in the HT group compared to the NT group (p<.05). Conclusions : These results suggest that muscle imbalance between TA and EDL muscle and decreased ankle dorsiflexion range of motion may contribute to hammer toe deformity. Further studies are needed to confirm that the correcting of this imbalance and the increasing ankle dorsiflexion could improve toe alignment in the subjects with HT.

• 터널과지하공간
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• 제19권4호
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• pp.328-338
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• 2009

암석 물성을 간접적으로 추정하기 위한 방법으로 슈미트 해머 타격법이 보편화되어 있다. 그러나 보고된 대부분의 방법들은 단일 타격법으로 오차를 많이 내포하고 있으며 연속 타격법의 경험식도 자료 처리방법에 불합리한 점들이 많아 범용하기 어려운 실정이다. 본 연구에서는 기존의 ASTM, ISRM, BSI, Poole와 Farmer 및 Hucka의 방법들을 검토하고, 국내에서 출토된 150개의 화성암, 변성암 및 퇴적암을 대상으로 시험을 시행하여 이들 방법들의 불합리한 점들을 수정, 보완하여 최적의 시험방법과 새로운 자료 처리방법을 제시하였다.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.338-347
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• 2010

Heunginjimun designated as a Treasure No.1 is a two-story wooden structure with 5 bay and 2 bay in its front and side views, respectively. This paper presents an investigation on vibration characteristics of Heunginjimun through both ambient vibration and impact hammer tests. Ambient vibration test was performed to identify the natural frequency of Heunginjimun from the spectrum analysis of time history. Impact hammer test was undertaken to find the frequency of Heunginjimun which is affected by the surrounding traffics and to verify the reciprocal principle for the wooden structural system. Ambient vibration test results of Heunginjimun showed that the natural frequencies in two principal axes 1.5 Hz and 1.1 Hz, respectively. It was confirmed from impact hammer tests for a ground that the frequency of 4.2 Hz is caused by the traffics surrounding Heunginjimun. It was also observed that from the impact hammer test results between two locations in Heunginjimun that the transfer functions measured from two corresponding locations coincided well with each other. This result shows that the wooden structural system is globally linear, and the reciprocal principle is established.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.411-418
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• 2002

In domestic road construction sites, the compaction control based on strength are widely performed through the direct method with high accuracy, such as Plate Loading Test or Field CBR test. It is impossible to manage all construction sites using the direct method because the direct method requires heavy reaction loads and long measurement time. Therefore, it is necessary to apply the indirect method that could control the relative density of construction sites on the whole. Indirect methods, such as Cone Penetration Test and Fall Cone Test, require extra time for data analyzing and fixed area for test device. In this paper, the field applicability of Soil Impact Hammer (SIH) was investigated comparing with the results of field measurement tests and laboratory compaction tests. SIH developed by Japan Construction Administration and Asanuma Ltd., is a kind of indirect methods for compaction checking. According to the results of SIH performed in domestic road construction site, the subgrade reaction modulus obtained from SIH are similar to that from Plate loading tests in the range of 10 to 40. In comparison with laboratory compaction test, similar compaction line are shown in the dry side of optimum moisture contents.

• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.28-38
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• 2016

The flexible control system for hydraulic pile hammer using main control valve is present to the requirement of rapidly reversing with high frequency. To ensure the working reliability of hydraulic pile hammer, the reversing performance of the main control valve should commutate robustness to various interfere factors. Through simulation model built in Simulink/Stateflow and experiment, the effects of relative parameters to reverse performance of main control are analyzed and the main interfere factors for reversing performance are acquired. Treating reverse required time as design objects, some structure parameters as control factors, control pressure, input flow and gaps between spool and valve body as interfere factors, the robust design of the main control valve is done. The combination of factors with the strongest anti-jamming capability is acquired which ensured the reliability and anti-jamming capability of the main control valve. It also provides guidance on design and application of the main control valve used in large flow control with interferes.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1978-1985
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• 2018

In this paper, a novel single-phase hybrid switched reluctance motor (HSRM) is proposed for hammer breaker application. The hammer breaker requires only unidirectional rotation and high-speed operation. To satisfy the requirements and eliminate torque dead-zone, the rotor of the proposed 4/4 poles SRM is designed with wider pole arc and non-uniform air-gap. This motor has a simple structure and produces low torque ripple. Permanent magnets (PMs) are mounted on the inner stator at a certain position which enables it to park the rotor for self-start and create positive cogging torque in the torque dead-zone. Compared with conventional single-phase switched reluctance motor, HSRM has an increased torque density and relatively low torque ripple. To verify effectiveness, finite element method (FEM) is employed to analyze the performance of the proposed structure. Then, the proposed motor is compared with the existing motor drive system for the same application. The proposed HSRM is easy to manufacture along with competitive performance.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3596-3601
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• 2015

진동해머에 의해 시공되는 말뚝의 거동을 분석할 목적으로 개발된 기존의 프로그램을 개선하고자 하였다. 진동해머-말뚝-지반으로 구성되는 진동시스템의 기존 지배방정식에 지반저항의 댐핑효과와 클러치마찰력을 추가하였다. 또한, 개발된 해석기법의 하중전이곡선을 모사하는 수정 Ramberg-Osgood 모델의 매개변수를 재산정하여 해석기법을 개선하고자 하였다. 수정된 프로그램에 의한 해석결과를 현장시험결과와 비교해 볼 때 시간에 따른 말뚝의 변위 및 하중전이거동이 현장시험결과에 좀 더 유사하였다. 개발된 프로그램에 의한 말뚝 관입깊이별 관입속도를 상용 프로그램에 의한 결과 및 현장시험결과와 비교해 볼 때 상용프로그램보다 훨씬 더 현장시험결과에 가까웠다.