Correction of constraint loss in fracture toughness measurement of PCVN specimens based on fracture toughness diagram

Choi, Shin-Beom,Chang, Yoon-Suk,Kim, Young-Jin,Kim, Min-Chul,Lee, Bong-Sang 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3

The aim of this paper is to suggest an approach to generate master curves by using miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimen, made of SA508 carbon steel. Firstly, fracture toughness diagram is derived from comparing finite element analyses results with the fixed mesh size at crack tip between standard compact tension and PCVN specimens. To compensate the constraint effects from different geometry, further examination based on the fracture toughness diagram was performed. In this context, a scale factor to deal with specimen size effects is proposed by statistically manipulating the numerical analysis data. Finally, the proposed scale factor is applied to calculate reference temperature which affects on the master curve. We expect that the approach can be applicable to compensate the geometrical constraint effects on fracture toughness of SA508 carbon steel when the PCVN specimen is used.

소형 굽힘 파괴인성 시편의 소성구속력 손실 보정에 미치는 구속조건의 영향

김만원(Maan-Won Kim),김민철(Min-Chul Kim),이봉상(Bong-Sang Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3

Attention has been paid to the use of small sized specimens for the fracture toughness test of nuclear power plant materials in particular. It has been reported that the stress fields ahead of the crack tip experience a reduction of triaxiality resulting in a constraint size effect when the relevant structural dimensions are not large relative to the zone of extensive plasticity. ASTM E1921, commonly referred to as the Master Curve method, describes a test procedure for measuring the fracture toughness in the transition region for ferritic steels and impose a fracture toughness limit to address the constraint effect. The limit is related to an assumption that the specimen ligament must be large enough to ensure a condition of high crack front constraint at fracture. This requirement is concerned with a constraint limit, 30, in an expression to define a maximum measurable facture toughness, K<SUB>Jc</SUB>. In this study, we utilized a small-scale yielding correction method based on the micro-mechanical scaling model to adjust the constraint loss at the crack front of the small sized pre-cracked Charpy V-notch(PCVN) specimens by using the finite element analysis and post-processing of the numerical and experimental results. We also studied the effect of the constraint limit on the results of constraint loss adjustment at the small sized PCVN specimens. The results showed loss of constraint at M≤100, which is much higer than the corresponding censoring limit of M=30 in the ASTM E1291.

격납건물 라이너 플레이트 열화상검사의 불균등 조사 보상과 서모그램 대비 개선

김준영(Chunyoung Kim),강성민(Seongmin Kang),정윤재(Yoonjae Chung),김옥환(Okhwan Kim),김원태(Wontae Kim) 한국비파괴검사학회 2024 한국비파괴검사학회지 Vol.44 No.2

본 논문은 원전 격납건물 라이너 플레이트(CLP)에 대해, 적외선열화상검사(TT) 적용시 광원의 불균 등 조사에 의한 문제점을 개선하기 위한 연구이다. 광열원을 활용한 위상잠금 열화상(LIT) 탐상 시스템을 구축하고, 목업 및 기준 시험편을 제작하였다. 램프의 불균등한 조사는 열화상이미지에 의도되지 않은 대비를 나타내며, 이에 대한 교정과 보상이 고려될 수 있다. 본 연구는 기준 시험편으로 LIT에서 광열원에 의한 불균등을 미리 확인하고, 열화상의 대비를 보상하여 균일화할 수 있는 두 가지 보상시트를 제시한다. 동일한 시스템과 탐상조건으로 목업 시험편을 탐상하고, 취득된 데이터에 대해 보상시트를 적용하며, 서모그램의 보상 전후 대비와 검출능을 비교하였다. 그 결과, 열화상이미지의 대비를 최대 1/2 수준으로 낮출 수 있으며, 결함 크기와 SNR 간의 추세선 R2값이 0.99 이상으로 비례성이 개선되었다. 향후 CLP에 대한 탐상기법과 장치개발에 활용될 수 있을 것으로 기대한다. This study aims to mitigate the effects of uneven irradiation from lamps during thermographic testing (TT) of containment liner plates (CLPs) in nuclear power plants. A lock-in thermographic (LIT) testing system was constructed, and mock-up and reference specimens were prepared. Halogen lamps exhibited uneven irradiation depending on their locations, leading to unintended contrast variations in thermograms. Therefore, various correction and compensation methods were considered. This study utilized the reference specimens to characterize the unevenness caused by the light source in the LIT inspection setup. Two compensation methods were introduced to address the contrast variations resulting from uneven irradiation in thermograms. Mock-up specimens were then inspected using the same system and conditions. A compensation algorithm was applied to the acquired data, and the impact on thermograms before and after compensation was assessed. The results indicate that the compensation algorithm reduced unintended contrast in the thermograms by up to 50%. Additionally, the R2 value of the linear trend equation exceeded 0.99, demonstrating improved proportionality between the defect size and SNR. The proposed method shows promise for CLP inspection and calibration of testing devices in the future.

Influence of a Regular, Standardized Meal on Clinical Chemistry Analytes

Gabriel Lima-Oliveira,Gian Luca Salvagno,Giuseppe Lippi,Matteo Gelati,Martina Montagnana,Elisa Danese,Geraldo Picheth,Gian Cesare Guidi 대한진단검사의학회 2012 Annals of Laboratory Medicine Vol.32 No.4

Background: Preanalytical variability, including biological variability and patient preparation, is an important source of variability in laboratory testing. In this study, we assessed whether a regular light meal might bias the results of routine clinical chemistry testing. Methods: We studied 17 healthy volunteers who consumed light meals containing a standardized amount of carbohydrates, proteins, and lipids. We collected blood for routine clinical chemistry tests before the meal and 1, 2, and 4 hr thereafter. Results: One hour after the meal, triglycerides (TG), albumin (ALB), uric acid (UA), alkaline phosphatase (ALP), Ca, Fe, and Na levels significantly increased, whereas blood urea nitrogen (BUN) and P levels decreased. TG, ALB, Ca, Na, P, and total protein (TP) levels varied significantly. Two hours after the meal, TG, ALB, Ca, Fe, and Na levels remained significantly high, whereas BUN, P, UA, and total bilirubin (BT) levels decreased. Clinically significant variations were recorded for TG, ALB, ALT, Ca, Fe, Na, P, BT, and direct bilirubin (BD) levels. Four hours after the meal, TG, ALB, Ca, Fe, Na, lactate dehydrogenase (LDH), P, Mg, and K levels significantly increased, whereas UA and BT levels decreased. Clinically significant variations were observed for TG, ALB, ALT, Ca, Na, Mg, K, C-reactive protein (CRP), AST, UA, and BT levels. Conclusions: A significant variation in the clinical chemistry parameters after a regular meal shows that fasting time needs to be carefully considered when performing tests to prevent spurious results and reduce laboratory errors, especially in an emergency setting. Background: Preanalytical variability, including biological variability and patient preparation, is an important source of variability in laboratory testing. In this study, we assessed whether a regular light meal might bias the results of routine clinical chemistry testing. Methods: We studied 17 healthy volunteers who consumed light meals containing a standardized amount of carbohydrates, proteins, and lipids. We collected blood for routine clinical chemistry tests before the meal and 1, 2, and 4 hr thereafter. Results: One hour after the meal, triglycerides (TG), albumin (ALB), uric acid (UA), alkaline phosphatase (ALP), Ca, Fe, and Na levels significantly increased, whereas blood urea nitrogen (BUN) and P levels decreased. TG, ALB, Ca, Na, P, and total protein (TP) levels varied significantly. Two hours after the meal, TG, ALB, Ca, Fe, and Na levels remained significantly high, whereas BUN, P, UA, and total bilirubin (BT) levels decreased. Clinically significant variations were recorded for TG, ALB, ALT, Ca, Fe, Na, P, BT, and direct bilirubin (BD) levels. Four hours after the meal, TG, ALB, Ca, Fe, Na, lactate dehydrogenase (LDH), P, Mg, and K levels significantly increased, whereas UA and BT levels decreased. Clinically significant variations were observed for TG, ALB, ALT, Ca, Na, Mg, K, C-reactive protein (CRP), AST, UA, and BT levels. Conclusions: A significant variation in the clinical chemistry parameters after a regular meal shows that fasting time needs to be carefully considered when performing tests to prevent spurious results and reduce laboratory errors, especially in an emergency setting.

이차전지 결함 검출용 CT (Computerized Tomography) 장비의 교정을 위한 기준 시편 및 교정 절차 개발

이재민(J. M. Lee),문성준(S. J. Mun),백상우(S. W. Baek),서민상(M. S. Seo),곽동근(D. G. Gwak),최우석(W. S. Choi),김진수(J. S. Kim),이동혁(D. H. Lee) Korean Society for Precision Engineering 2023 한국정밀공학회 학술발표대회 논문집 Vol.2023 No.11

비선형 위상배열 영상화를 위한 시스템 비선형성 개선

박춘수(Choon-Su Park),David Roue,Pierre Calmon 한국비파괴검사학회 2020 한국비파괴검사학회지 Vol.40 No.3

비선형 위상배열 초음파 영상은 기존의 선형 위상배열 영상에서는 검출할 수 없는 결함을 보여줄 수 있다. 특히, 비선형 저조파 영상은 결함이 발생하였으나 외력이나 잔류 응력 등에 의해 닫혀 있어 기존의 선형 초음파 기법으로는 검출할 수 없는 닫힘 결함을 찾아낼 수 있다. 이러한 초음파의 비선형적 거동을 잘 관찰하기 위해서는 시스템의 비선형성을 파악하는 것이 필요하다. 시스템 비선형성에 영향을 주는 요인을 파악할 수 있으면, 이를 개선할 수 있는 방안도 도출할 수 있기 때문이다. 본 논문에서는 비선형 영상화를 위한 시스템의 비선형성을 정의하고, 이 비선형성에 영향을 미치는 인자 중 가진 신호의 주기 수(number of cycle)의 영향을 알아본다. 초음파 영상에서 신호의 주기 수는 영상의 공간해상도와 직접적으로 관련되기 때문에 비선형성 개선과 공간해상도를 동시에 고려하여야 한다. 시스템 비선형 특성을 교차배열 변환기를 이용해 살펴보고, 개선되는 정도를 정량화하여 관찰하였다. Nonlinear ultrasonic phased array imaging can reveal hidden cracks from linear imaging. In particular, nonlinear subharmonic imaging is well known for detecting closed cracks whose surfaces return into contact with each other through resilient forces. This enables ultrasound waves to pass through the cracks without reflection but generates lower harmonics of excitation frequency. Identifying system nonlinearity for recognizing the nonlinear behavior of ultrasound from the closed crack is extremely important. In this study, system nonlinearity for nonlinear imaging is defined, and the effect of the number of signal cycles on system nonlinearity is particularly observed. Increasing the number of cycles lowers system nonlinearity but decrease the spatial resolution of ultrasound imaging. Therefore, it should be carefully selected for compromise between them. An interleaved array transducer for multifunctional phased array imaging is employed to observe the enhanced system nonlinearity in nonlinear phased array imaging.