• 한국정밀공학회지
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• 제18권5호
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• pp.105-111
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• 2001

The creep crack growth properties in 3.3NiCrMoV steel were investigated at 55$0^{\circ}C$ by using CT specimen under constant load and constant Ct condition that was held during crack growth of Imm distance. Ct lelied on load line displacement rate, C＊usually increased with crack length though load is reduced in order to maintain constant Ct value as crack growth and appeared scatter band. At constant load and Ct region, crack growth slope was 0.900 and 0.844 each, on the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip increased as Ct increase to the critical value, and after that value FCA decreased. For the tertiary creep stage of crack growth test, the most of displacement was due to the steady state creep, except only small part due to the primary creep and other effects. Therefore, tests were mainly interrupted in the tertiary stage to obtain high value of Ct.

• 대한핵의학회지
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• 제39권4호
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• pp.263-265
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• 2005

A 25 years old male patient with Hodgkin's disease, considered as complete remission, underwent $^{18}F$-FDG whole body PET/CT. $^{18}F$-FDG whule body PET/CT showed unexpected hypermetabolic nodule in left quadratus femoris muscle suggesting local recurrence. Subsequent MRI also revealed well-enhancing nodular lesion with intermediate and high signal intensity on T1WI and T2WI, respectively. The lesion was confirmed as nodular fasciitis by pathologic examination of the excited specimen.

• Nuclear Medicine and Molecular Imaging
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• 제42권5호
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• pp.410-413
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• 2008

A 56 years old woman referred to our hospital with dysphagia and epigastric soreness. Gastroendoscopy revealed huge submucosal tumor with ulceration extending from distal esophagus to lesser curvature of stomach. Subsequent computed tomography(CT) demonstrated soft tissue mass encircling distal esophagus, and 18F-FDG PET/CT demonstrated intense $^{18}F-FDG$ accumulation in it. Finally this case was diagnosed as esophageal leiomyoma based on pathologic evaluation of the surgical specimen.

• 한국방사선학회논문지
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• 제17권5호
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• pp.651-662
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• 2023

본 연구에서는 검출기의 중심축을 자동 보정하는 초소형 CT를 설계 및 제작하고 성능을 검증하였다. 3D CAD 데이터와 초소형 CT 검출기 중심축을 수동으로 보정하여 촬영한 X-ray 데이터를 사용하여 3차원 재구성 성능을 평가하였다. 그 결과, 중심축이 0.25° 이상 기울면 원형 깨짐 현상이 발생하면서 3차원 재구성 영상의 품질이 급격히 저하된다는 사실을 발견하였다. 검출기 중심축 자동보정 장치를 적용하여 검출기 중심축이 시편 회전축과 일치하도록 보정하여 3차원 재구성 성능을 향상시켰다.

• 대한기계학회논문집A
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• 제26권5호
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• pp.890-895
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• 2002

Cold expansion method is retarded of crack initiation due to the compressive residual stress developed on the hole surface. Previous research has just been study about residual stress distribution in the hole surrounding. But, The purpose of this study was to improve the understanding of the residual stress effect in hole surrounding as crack growth from another hole. In this paper, it is shown that residual stress is redistributed due to the application of cold expansion process for CT specimen using finite element method. It is further shown that tensile stress increases in proportion to cold expansion ratio in the vicinity of crack. It is thought that stress intensity factor increases with cold expansion ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.855-861
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• 2005

Fracture toughness defined near the initiation of stable crack growth is investigated by R-curve and Direct Current electric Potential Determination(DCPD) under mode I plane strain conditions for CT specimen with 25.4mm thickness of SS400 steel. Fracture toughness. $J_{IC}$lit near crack tip of CT specimen by R-curve is 17.14 $kg_{f}/mm$ and however. its value by DCPD is 22.82 $Rg_{f} mm$ The value of fracture toughness by DCPD is larger than that by R-curve. Therefore, it is suggested that the evaluation of fracture toughness by R-curve is optimum than by DCPD, when considering amount of crack growth about each of fracture toughness.

• 한국생산제조학회지
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• 제8권1호
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• pp.119-125
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• 1999

The distribution of fatigue crack growth rate is subjected to the measuring interval and calculated method of growth rate. In this paper, in order to establish the method of determining the distribution of fatigue crack growth rate, which ignores those influences, a series of fatigue crack growth experiments and measuring intervals of crack length calculated reasonable are presented. The main conclusions obtained are summarized as follows: 1) As a result of the ΔP constant test and ΔK constant test, it is thought that an approximate measuring interval of 0.3~0.7mm is reasonable, which allows for few errors and is little subjected to the calculated method of crack growth rate. 2) After generally comparing the error estimation by using the experimental data of CCT specimen with the error rating of the CT specimens, it is possible that the fatigue test has few errors within the measuring interval, ξ(Δa/W)=0.0067~0.017, regardless of the dimension of specimen geometry.

• 한국해양공학회지
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• 제9권1호
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• pp.132-141
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• 1995

The purpose of the present study is to investigate the statistical characteristics of m and C in the fatigue crack propagation law, da/dN=C(.DELTA.K)/sup m/ and to studies on the randomness of fatigue crack propagation and retardation behavior. Fatigue tests were perfomed on 32 CT specimens of SPV50 steel under the same one condition. First, the value of m and C were determined for each specimen, and all the data were analyzed statistically. second, the material's resistance to fatigue crack propagation is modeled as a stchastic process, which varies randomly along the crack path. The statistical analysis of the material resistance is performed with the data obtained by constant load controlled tests. Finally, retardation behavior was examined experimentally by using a CT specimen, and a retardation parameters were analyzed statistically.

• 한국해양공학회지
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• 제9권1호
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• pp.111-119
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• 1995

The elastic-plastic fracture toughness($J_{IC}$) and fracture resistance (J-R curve) of SA508-3 alloy steel used for nuclear reactor pressure vessel are investigated by using CT-type specimens. Fracture toughness tests are conducted by unloading compliance method and multiple specimen method at room temperature, -2$0^{\circ}C$ and 20$0^{\circ}C$. The apparent negative crack growth phenomenon which usually arises in partial unloading compliance test is well known. The negative crack growth phenomenon in determining J sub(IC) or J-R cure from partial unloading compliance experiments may be eliminated by the offset technique. In this study, the evaluation of $J_{IC}$ multiple specimen method recommended by the JSME gives the most reliable results by using half-size CT(similar-type) specimens.

• 동력기계공학회지
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• 제5권2호
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• pp.50-56
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• 2001

In this study, the effect of specimen thickness and stress ratio on fatigue crack growth in S45C steel was investigated. Acoustic emission was monitored during the fatigue crack growth test. Both crack closure and AE technique were used in assessing fatigue crack growth behavior. Constant amplitude loading tests were performed on CT type specimen with three different thicknesses and stress ratios. Crack closure was investigated to explain the influence of specimen thickness and stress ratio on the fatigue crack growth in the second growth region. The crack closure effect was decreased with specimen thickness and stress ratio.