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최재강,임만배 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4
In this study, under large scale yielding conditions crack propagation is found to governed by parameters based on the J-integral or on the crack opening displacement. But initiation of crack propagation of ductile material seems to be controlled by just on parameter that is the strain. The relationship between the critical value of J-integral and the local fracture strain in uniaxial tensile test in the region of maximum reduction in area. Therefore, the fundamental theoretical equation by the proposed elastic-plastic fracture toughness and the local fracture strain has a merit, in comparison with the ASTM method, which can measure by using the load-displacement curve and the specimens in tensile test.
최재강,안광주 한국산업안전학회 1997 한국안전학회지 Vol.12 No.3
To evaluate the elastic-plastic fracture toughness by this modified offset method, the origin of J-R curve is set with drawing the blunting line on the maximum point of the negative crack growth and R curve is modified by adding the blunting factor of the experimented point on the R curve. The elastic-plastic fracture toughness J_(IC) of A5083-H112 material by the modified offset method are 44kN/m on the smooth CT specimens.
안광주,이상봉,최재강 東義大學校 産業技術開發硏究所 1996 産業技術硏究誌 Vol.10 No.-
In this study the elastic-plastic fracture toughness J???? for ion-nirided structural steel SS41 has been estimated with the single specimen unloading compliance techniques and focused on the J???? values of CT specimens through a comparison of the normalized with the ion-nitrided. The results throughout the evaluation of fracture toughness J???? were obtained as follows ; 1) In the ASTM E 813-92 R-curve method. J??? value for the nomalized CT specimen was evaluated as J???=440kN/m but its value is invalid for the J???? in respect to the effective conditional requirements. 2) In the ASTM E 813-92 R-curve method. J??? values for the ion-nitrided CT specimen were evaluated as 275 kN/m and 280 kN/m, respectively and it values is valid for the elastic plastic fracture toughness J????. 3) J???? evaluation for high ductile materials had better use of the measured blunting line rather than the assumed blunting line in the ASTM E 813-92. 4) In the cases of high ductile materials. The best fitting curve for the R-curve is able to give as y=cx??? and y=a+bx???, and they can apply efficiently to evaluate J????.
제하컴플라이언스법에 의한 A5083 알루미늄합금의 탄소성파괴인성 평가
안광주,최재강 東義大學校 産業技術開發硏究所 1997 産業技術硏究誌 Vol.11 No.-
A 5083-H112 aluminum alloy in AI-Mg group is an important material and used for manufacturing a LNG tank which transports the liquified natural gas. In this investigation, the elastic- plastic fracture toughness of this material is evaluated by an unloading compliance method according to the ASTM E813-89 method on the smooth and side groove ?CT specimens. The effect of heat treatment (annealing and quenching) and welding is studied on the elastic-plastic fracture toughness. A modified offset method is proposed for the negative crack due to the negative crack effect.
금속 재료의 피로 균열 전파 속도(da/dN)평가를 위한 변형율 확대 계수의 유효성 검토
유재환,최재강,손종동 한국산업안전학회 1996 한국안전학회지 Vol.11 No.2
Fatigue fracture is the cyclic fracture phenomena at a very small local area near a crack tip. Therefore, the detailed quantitative experimental analysis about local cyclic strain distribution near a crack tip is prerequisite in order to make an effective parameter able to account for fatigue fracture problems. However, there are few reporta on detailed quantitative experimental analysis of a local cyclic strain distribution near a crack tip, because of experimental difficulties. In this study, the distribution of local fatigue strains near a fatigue crack tip was in detail studied using by fine dot grid strain measurement method. From these results, a single parameter, which characterizes local fatigue strain field, was proposed. In addition, this parameter was applied to evaluate the fatigue crack propagation rate.
안광주,최재강,박준수 한국산업안전학회 1999 한국안전학회지 Vol.14 No.3
This paper were performed to evaluate the elastic-plastic fracture toughness J_(IC) by the unloading compliance method for 1/2 CT specimen of A5083-H112 aluminum alloy. A modified offset method for negative crack growth effect is presented and compared with Voss offset method. We found that the modified offset method presented can be used efficiently for a determination of the stable crack onset. The J_(IC) by Voss offset method can be overestimated, but the suggested offset method showed a high reliability within 5% of tolerence from the results by the multi-specimen method.
안광주,박일주,최재강,원종식 東義大學校産業技術開發硏究所 1993 産業技術硏究誌 Vol.7 No.-
IIn this paper, the elastic-plastic fracture toughness J₁c of a structural steel SS41 was discussed. The main efforts were focussed on the comparison of the J₁c values determined by the ASTM R-curve method, the JSME R-curve method, the ASTM partial unloading compliance method, and impact test method. In parallel with this efforts, however, measurements were also made simulaneously to detect the relationship between △aASTM,△aJSME and △a21. The results obtained are as follows ; 1) A relation between △aASTM,△aJSME and △a21 for each specimen shows that the following linear equation stands △aASTM=1.0533 △a21 △aJSME=1.4478 △a21 and it is ascertained that the △aASTM is a simple reliable method in the evaluation of crack extension. 2) In the ASTM E 813-81 R-curve method, the valid ?? values are obtained as JQ=165.18 kN/m, while on the other hand, in the ASTM E 813-88 method the JQ values are not obtained because there is no J-△a point between a line parallel to the blunting line at an offset of 1.0mm and the 1.5mm exclusion line. Hence, the ASTM E 813-81 R-curve method is more desirable than the ASTM E 813-88 R-curve method. 3) In the partial unloading compliance method, the JQ values obtained by E 813-81 and E 813-88 are more excessively estimated by 9.9% and 24.3% than those by the JSME R-curve method. On the other hand the J₁c values by the modified E 813-88 method which proposed by Carlson are fairly close to those by the JSME R-curve method. So the modified E 813-88 method is desirable to estimate the J₁c value of structural steel. 4) The J₁c values by the impact test method has 13% deviation from those by the ASTM E 813-81 R-curve method in SS41 specimens. However the impact test method also can be used as a reliable method in case the correction factor adopted.