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Analysis of Necking Deformation and Fracture Characteristics of Irradiated A533B RPV Steel
김진원,THAK SANG BYUN 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.8
This paper reports the irradiation effect on the deformation behavior and tensile fracture properties of A533B RPV steel. An inverse identification technique using iterative finite element (FE) simulation was used to determine those properties from tensile data for the A533B RPV steel irradiated at 65 to 100ºC and deformed at room temperature. FE simulation revealed that the plastic instability at yield followed by softening for higher doses was related to the occurrence of localized necking immediately after yielding. The strain-hardening rate in the equivalent true stress–true strain relationship was still positive during the necking deformation. The tensile fracture stress was less dependent on the irradiation dose, whereas the tensile fracture strain and fracture energy decreased with increasing dose level up to 0.1 dpa and then became saturated. However, the tensile fracture strain and fracture energy still remained high after high-dose irradiation, which is associated with a large amount of ductility during the necking deformation for irradiated A533B RPV steel.
Evaluation methods for the hoop strength of small-sized tubular ceramic components
Hong, Seong-Gu,Byun, Thak-Sang,Snead, Lance L.,Lee, Chong Soo Cambridge University Press (Materials Research Soc 2009 Journal of materials research Vol.24 No.4
<P>Miniaturized test methods were developed and applied to measure the hoop strength of small tubular components. A diametrical loading method and an internal pressurization method using elastomeric insert were adopted in the development of testing methods. Detailed analyses to assess these testing methods were attempted by using theoretical solutions and finite element analysis for stress distributions and the characteristics of the Weibull statistics. To demonstrate the applicability of the test methods, commercially available alumina tubes and miniature silicon carbide coatings from surrogate nuclear fuel particles were tested and their fracture strength distributions were analyzed with Weibull statistics. The size scaling relationship on the fracture strength was investigated by correlating with effective surface area. Furthermore, the applicability of the testing methods was discussed in terms of multiaxial stress fields, altered stress distribution by flattened loading contact, and availability of insert, focusing on high-temperature applications.</P>
A comparative study on the wear behaviors of cladding candidates for accident-tolerant fuel
Lee, Young-Ho,Byun, Thak Sang Elsevier 2015 Journal of nuclear materials Vol.465 No.-
<P><B>Abstract</B></P> <P>Accident-tolerant fuels are expected to have considerably longer coping time to respond to the loss of active cooling under severe accidents and, at the same time, have comparable or improved fuel performance during normal operation. The wear resistance of accident tolerant fuels, therefore, needs to be examined to determine the applicability of these cladding candidates to the current operating PWRs because the most common failure of nuclear fuel claddings is still caused by grid-to-rod fretting during normal operations. In this study, reciprocating sliding wear tests on three kinds of cladding candidates for accident-tolerant fuels have been performed to investigate the tribological compatibilities of self-mated cladding candidates and to determine the direct applicability of conventional Zirconium-based alloys as supporting structural materials. The friction coefficients of the cladding candidates are strongly influenced by the test environments and coupled materials. The wear test results under water lubrication conditions indicate that the supporting structural materials for the cladding candidates of accident-tolerant fuels need to be replaced with the same cladding materials instead of using conventional Zirconium-based alloys.</P>
ANALYSIS OF NECKING DEFORMATION AND FRACTURE CHARACTERISTICS OF IRRADIATED A533B RPV STEEL
Kim, Jin Weon,Byun, Thak Sang Korean Nuclear Society 2012 Nuclear Engineering and Technology Vol.44 No.8
This paper reports the irradiation effect on the deformation behavior and tensile fracture properties of A533B RPV steel. An inverse identification technique using iterative finite element (FE) simulation was used to determine those properties from tensile data for the A533B RPV steel irradiated at 65 to $100^{\circ}C$ and deformed at room temperature. FE simulation revealed that the plastic instability at yield followed by softening for higher doses was related to the occurrence of localized necking immediately after yielding. The strain-hardening rate in the equivalent true stress-true strain relationship was still positive during the necking deformation. The tensile fracture stress was less dependent on the irradiation dose, whereas the tensile fracture strain and fracture energy decreased with increasing dose level up to 0.1 dpa and then became saturated. However, the tensile fracture strain and fracture energy still remained high after high-dose irradiation, which is associated with a large amount of ductility during the necking deformation for irradiated A533B RPV steel.
페라이트-마르텐사이트-베이나이트 강의 파괴인성에 미치는 미세조직의 영향
김인섭,변택상 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.6
The effect of microstructure on the fracture toughness of ferrite-martensite bainite steels was investigated with Fe-0.11C 1.64Mn-0.78Si composition. One inch compact tension specimens (1T-CTSs) were machined from hot rolled plates. The microstructure of ferrite-martensite-bainite was introduced to the specimens by the heat treatment of inter critical annealing at 800˚C and isothermal holding at 350C Holding at 350 C increased volume fraction of bainite. while decreased that of martensite, and refined martensite particles. Single specimen unloading compliance method was used in fracture test to obtain J-resistance (J-R) curve and to determine the fracture toughness(J_(IC)). Introduction of bainite to the ferrite-martensite steel1 improved the fracture toughness due to the deformation of bainite which relaxed the stress concentration on the interface of ferrite and martensite. Observation of fractgraphs through the scanning electron microscope (SEM) identified the fracture mechanism of ferrite- martensite-bainite steels as dimple nucleation and crack growth by decohesion of ferrite matrix and second phase particles and by mi crovoid coalescence.