• 대한기계학회논문집A
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• 제39권4호
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• pp.383-390
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• 2015

본 논문에서는 원전 배관 재료의 변형거동에 미치는 하중속도의 영향을 파악하기 위해서, SA508 Gr.1a 저합금강과 SA312 TP316 스테인리스강 배관재를 대상으로 상온과 원전 운전온도인 $316^{\circ}C$에서 다양한 변형률 속도로 인장시험을 수행하였다. 시험 결과, 상온에서는 두 배관재의 변형거동이 일반적인 하중속도 의존성을 보였다. 즉, 하중속도가 증가함에 따라 강도는 증가하고 연성은 감소하는 경향을 보였다. 그러나, $316^{\circ}C$에서는 하중속도가 증가함에 따라 SA508 Gr.1a 저합금강의 강도와 연신률이 모두 감소하였고 단면수축률은 감소 후 증가하는 비선형 거동을 보였다. SA312 TP316 스테인리스강의 강도, 연신률, 그리고 단면수축률은 하중속도에 관계없이 거의 일정한 값을 보였다. 시험 온도에 관계없이 SA508 Gr.1a 저합금강의 가공경화능력은 하중속도에 거의 영향을 받지 않았으나, SA312 TP316 스테인리스강에서는 하중속도가 증가함에 따라 가공경화능력이 감소하였다.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• 한국압력기기공학회 논문집
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• 제13권1호
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• pp.75-83
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• 2017

This study investigated deformation behavior of major nuclear structural materials under cyclic loading conditions via cyclic stress-strain test. The cyclic stress-strain tests were conducted on SA312 TP316 stainless steel and SA508 Gr.3 Cl.1 low-alloy steel, which are used as materials for primary piping and reactor pressure vessel nozzle respectively, under cyclic load with constant strain amplitude and constant load amplitude at room temperature (RT) and $316^{\circ}C$. From the results of tests, the cyclic hardening and softening behavior, stabilized cyclic stress-strain behavior, and ratcheting behavior of both materials were investigated at both RT and $316^{\circ}C$. In addition, appropriate considerations for cyclic deformation behavior in the structural integrity evaluation of major nuclear components under excessive seismic condition were discussed.

• Corrosion Science and Technology
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• 제13권3호
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• pp.87-94
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• 2014

Recently, the application of bending products has been increased since the industries such as automobile, aerospace, ships, and plants greatly need the usage of pipes. For facility fabrication, bending process is one of key technologies for pipings. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. Because of local heating and compressive strain, detrimental phases may be precipitated and microstructural change can be induced. This work focused on the effect of induction heat bending process on the properties of ASME SA312 TP316 stainless steel. Evaluation was done on the base metal and the bended areas before and after heat treatment. Microstructure analysis, intergranular corrosion test including Huey test, double loop electropotentiokinetic reactivation test, oxalic acid etch test, and anodic polarization test were performed. On the base of microstructural analysis, grain boundaries in bended extrados area were zagged by bending process, but there were no precipitates in grain and grain boundary and the intergranular corrosion rate was similar to that of base metal. However, pitting potentials of bended area were lower than that of the base metal and zagged boundaries was one of the pitting initiation sites. By re-annealing treatment, grain boundary was recovered and pitting potential was similar to that of the base metal.

• 대한기계학회논문집
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• 제18권5호
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• pp.1106-1116
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• 1994

Leak Before Break(LBB) design concept is applied to piping systems of newly-built Yonggwang 3, 4 nuclear generating stations as a design alternative to the provision of pipe whip restraints, in recognition of the questionable benefits of providing such restraints. The objective of this paper is to evaluate the material properties (tensile and fracture toughness) of SA312 TP316 stainless steel and their associated welds manufactured for shutdown cooling system of Yonggwang 3, 4 nuclear generating stations. Effect of various parameters such as specimen orientation, test temperature, welding on material properties were examined.