• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.1
• /
• pp.7-11
• /
• 2012

For fault detection about the abrasion stage of rotational machineries under the dynamic loading conditions unlike the traditional diagnosis method used in the past decade, the infrared thermographic method with its distinctive advantages in non-contact, non-destructive, and visible aspects is proposed. In this paper, by applying a rotating deep-grooved ball bearing, passive thermographic experiments were conducted as an alternative way to proceeding the traditional fault monitoring on spectrum analyzer. As results, the thermographic experiment was compared with the traditional vibration spectrum analysis to evaluate the efficiency of the proposed method. Based on the results obtained as NDT, the temperature characteristics and abnormal fault detections of the ball bearing according to the abrasion stage were analyzed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.2
• /
• pp.1-7
• /
• 2002

A procedure for determination of performance point was developed based on the concept of the direct displacement-based design method. Using the proposed procedure, parametric study has been performed for various natural periods of the structure, yield strength, and the stiffness after the first yield. The proposed method was also applied to a 10-story steel frame, and the results were compared to those from the capacity spectrum method and the time history analysis. It was found from the comparison that there were good agreement between the results.

• Journal of Industrial Technology
• /
• v.24 no.A
• /
• pp.195-204
• /
• 2004

To evaluate inelastic seismic responses of multi-span bridge structures, the capacity spectrum method(CSM) incorporating the equivalent single-degree-of freedom(ESDOF) method is presented. Application of the CSM incorporating the ESDOF method is illustrated by example analysis for symmetric and asymmetric bridge structures. To investigate an accuracy of the CSM, the maximum displacements estimated by the CSM are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the CSM provided conservative estimates of the maximum displacements for the symmetric and asymmetric bridge structures, and the trend of conservative estimates of the asymmetric bridge structures was significantly larger than that of the symmetric bridge structure.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.2
• /
• pp.75-84
• /
• 1997

The up-to-date fatigue strength assessment system for ship structures was developed based on the spectral analysis method and numerical calculation for a membrane type LNG carrier was carried out to verify the effectiveness of the developed system. The wave induced loads acting on the ship's hull were calculated based on strip theory. And introducing the concept of influence factor and 3-D fine mesh structural analysis, direct calculation of long-term distribution of wave induced stress components was realized. Using the derived long term distribution of stress components and Miner-Parmgren's linear damage accumulation rule, fatigue strength of structural components were investigated.

• Science of Emotion and Sensibility
• /
• v.2 no.1
• /
• pp.157-168
• /
• 1999

슈트용 직물을 대상으로 직물이 스치는 소리를 재현하여 이를 녹은하고 FFT 분석을 통하여 얻은 음향 스펙트럼을 기초로 음색을 정량화할 수 있는 요인을 개발하여, 음색 요인과 KES system에 의해 측정한 직물의 물리적 성진 간의 관계를 고찰하고자 하였다. 직물 소리의 음향 스펙트럼을 기초로 하여 최고 음압과 최저 음압의 차이인 ΔL과 최고와 최저 음압에 해당되는 주파수 간 차이인 Δf, 총음압 LPT의 세가지 요인을 음색 요인으로 정하여 각 직물의 음색 요인 값을 추출하였고, KES를 이용하여 각 직물의 17개의 물리적 성질의 수치를 구하였다. 세 가지 음색 요인과 직물의 물리적 성질 간의 상관관계에서 ΔL은 직물의 인장 회복력과 두께와 유의적인 상관관계를 Δf는 직물의 인장 선형성화 전단성질, 압축에너지, 무게와 유의적인 상관관계를 보이며, LPT는 최대하중시 신장성, 인장 선형성, 인장 에너지와 유의적인 상관관계를 보이는 것으로 나타났다. 세 가지 음색 요인과 직물의 물리적 성질 간의 단계별 희귀관계에서는 LPT가 직물의 물리적 성직(EM, MIU, RC, LT)에 의해 가장 잘 설명되는 것으로 나타났다. 이와 같은 결과를 바탕으로 본 연구에서 시도한 절량화된 음색은 직물의 물리적 성질과 유의한 관계를 가짐을 확인하였다.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.3 s.49
• /
• pp.65-75
• /
• 2006

Nonlinear pushover analysis is used to evaluate the earthquake response of building structures. To accurately predict the inelastic response of a structure, the prescribed story load profile should be able to describe the earthquake force profile which actually occurs during the time-history response of the structure. In the present study, a new modal combination method was developed to predict the earthquake load profiles of building structures. In the proposed method, multiple story load profiles are predicted by combining the modal spectrum responses multiplied by the modal combination factors. Parametric studies were performed far moment-resisting frames and walls. Based on the results. the modal combination factors were determined according to the hierarchy of each mode affecting the dynamic responses of structures. The proposed modal combination method was applied to prototype buildings with and without vertical irregularity. The results showed that the proposed method predicts the actual story load profiles which occur during the time-history responses of the structures.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.5 no.4
• /
• pp.67-77
• /
• 2002

This paper introduces the calibration results of the fatigue crack growth models for damage tolerance analysis of the aircraft structures. Generalized Willenborg model and Wheeler model are calibrated with experimental data tested under the load spectrum of a trainer. The retardation factors such as, shut-off ratio in Generalized Willenborg model and shaping exponent in Wheeler model, are evaluated for aluminum alloys AL2024-T3511, AL7050-T7451 and AL7075-T73511. It is shown that the retardation effect of the crack growth rate depends on the yield strength of material and the maximum stress in the load spectrum. Generalized Willenborg model and Wheeler model give satisfactory prediction of crack growth life but the calibration of the experimental parameters with test is required.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.768-772
• /
• 1994

공작기계의 주축은 최근 고속화,고정밀화 및 고강성화되어가는 경향이 커지고 있다. 이러한 경향에 따라서 주축의] 설계는 매우 중요하며, 주축용 베어링은 앵귤러 콘택트 볼베어링이 많이 사용되고 있다. 공작기계의 주축은 고속 회전에 따른 고강성의 필요성이 증대하게 되고, 고상성을 얻기 위하여 축 방향의 일정한 예압을 주게된다. 이 예압량은 결국 축 방향의 하중이므로 주축용 베어링의 수명을 변화 시키게 된다. 따라서 축 방향 하중의 변화에 따른 베어링의 수명 특성을 파악하여야 하며, 적절한 베어링 수명의 판단을 통해 기계의 보수 및 관리에 관한 재경비를 절감할 수 있다. 그러므로 본 연구에서는 실험을 통해 베어링의 특성 주파수를 이끌어 내고 주파수 스펙트럼 분석을 이용하여 베어링의 상태를 진단하 는 기본겆인 데이터를 얻는다.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.385-389
• /
• 2004

Test facilities for the wind turbine performance monitoring and mechanical load measurements are installed in Vestas 100 kW wind turbine in Wollyong test site, Jeju island. The monitoring system consists of Garrad-Hassan T-MON system, telemetry system for blade load measurement, various sensors such as anemometer, wind vane, strain gauge, power meter, and etc. The experimental procedure for the measurement of wind turbine loads, such as edgewise(lead-lag) bending moment, flapwise bending moment, and tower base bending moment, has been established. Strain gauges are on-site calibrated against load cell prior to monitoring the wind turbine loads. Using the established monitoring system, the wind turbine is remotely monitored. From the measured load data, the load analysis has been performed to obtain the load power spectral density and the fatigue load spectra of the wind turbine.

• Journal of the Society of Naval Architects of Korea
• /
• v.44 no.4
• /
• pp.425-438
• /
• 2007

In this paper, unsettled technical controversies concerning about fatigue strength analysis for FPSO, one of the representative floaters, associated with welding types, screening methods, fabrication tolerances, corrosion margins and Morison loads are described based on yard practices. Basic theory for stochastic fatigue analysis is introduced as detail as possible. In order to resolve large parts of the controversies, a new fully stochastic fatigue analysis program for FPSO is developed.