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고한서(H. S. Ko),박광희(K. H. Park),서형렬(H. -R. Seo),하종수(J. -S. Ha) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Thermal error compensation has been developed for CNC (Computer Numerical Control) machining center with moving heat sources. The thermal error in CNC machining center has an effect on machining accuracy more than the geometric error does. Thus, temperature distributions of a spindle unit have been analyzed numerically by a Finite Differential Method and experimentally by an infrared (IR) camera in this study. A multiple variable method has been derived to estimate the thermal deformation of the machine origin stably and effectively after measuring deformation and temperature data. The experimental results for a vertical machining center have shown that the thermal errors of the machine origins were reduced more than 30% by the developed method.
박광희,박종현,안희성,박치승 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.2
It has not been performed to inspect the underclad cracking in Korea nuclear plant since there is no Code Requirments for inspection. However, underclad cracks in nuclear pressure vessels were reported firstly in 1970. The objection of this study is to be established the ultrasonic inspection techniques for underclad cracking. The ultrasonic inspection of bimetalic stainless steel weld is very difficult by high attenuation and multiple scattering at weld surface and weld/base metal interface. The various inspection methods using 70。 refracted longitudinal wave. 50/70 tandem transducer, 45。 and 60。single shear wave are compared. Experiments on limited specimens applied same condition to nuclear pressure vessels shows that 70。refracted longitudinal wave method is the best one for the detection of underclad cracks. 50/70 tandem transducer using SPOT(Satellite Pulse Observation Technique) is more effective for underclad crack sizing than other sizing methods.
원자로 In-Core Flux Thimble 결함의 와전류 탐상 기술 개발
박광희,임창재,장윤영,박승식 한국비파괴검사학회 1990 한국비파괴검사학회지 Vol.10 No.2
Since in-core flux thimble tube wear the due to flow-induced vibration could degrade the integrity of nuclear reactor, the effective detection and interpretation of the wear is important. In order to establish an inspection technique for thimble tubes, an eddy current experiment was performed to determine the optimum test frequency, defect sensitivity and evaluation accuracy. Eddy current probes were designed and fabricated with a theory. Specimens with artificial defects were fabricated using electro discharge machining method. The results from inspection technique developed and on-site inspection showed good applicability.
초음파를 이용한 Austenitic Stainless Steel 용접부의 결함검출에 관한 기초적 연구
윤광식,박광희,박문호,서동만 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.1
This paper presents the ultrasonic characteristics of weldment and detectability of defects of weldment in Austenitic Stainless Steel Type 304 that is composed of mostly coolant piping system in nuclear power plants. The results of this experient shows as follows : 1. When the ultrasonic beam detects the detects on the side of base metal and on the opposite side of weldment, the indications which was detected on the screen show different amplitude and different metal path each. 2. The ultrasonically estimated notch depth is generally oversized than actual notch depth. 3. It is easy for the false indication to show up on the screen because of columnar structure of weldment in austenitic stainless steel. 4. The higher frequencies of transducer have more difficulties to detect the defects of the opposite side of weldment because of ultrasonic attenuation in weldment and the longitudinal transmitter-receiver transducer in the most effective in detecting the opposite side defects of weldment.