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Park, Chi-Yong;Lee, Hwee-Sueng;Huh, Nam-Su
- Transactions of the Korean Society of Mechanical Engineers A
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- v.38 no.2
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- pp.177-184
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- 2014
In this study, we investigated the variations in welding residual stresses in dissimilar metal butt weld due to width of repair welding and re-distribution behaviors resulting from similar metal welding (SMW) and mechanical loading. To this end, detailed two-dimensional axi-symmetric finite element (FE) analyses were performed considering five different repair welding widths. Based on the FE results, we first evaluated the welding residual stress distributions in repair welding. We then investigated the re-distribution behaviors of the residual stresses due to SMW and mechanical loads. It is revealed that large tensile welding residual stresses take place in the inner surface and that its distribution is affected, provided repair welding width is larger than certain value. The welding residual stresses resulting from repair welding are remarkably reduced due to SMW and mechanical loading, regardless of the width of the repair welding.
https://doi.org/10.3795/KSME-A.2014.38.2.177 인용 PDF KSCI

Song, Tae-Kwang;Chun, Yun-Bae;Oh, Chang-Young;Bae, Hong-Yeol;Kim, Yun-Jae;Lee, Sang-Hoon;Lee, Kyoung-Soo;Park, Chi-Yong
- Transactions of the Korean Society of Mechanical Engineers A
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- v.33 no.7
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- pp.664-672
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- 2009
Nozzle in nuclear power plant is connected to pipe using safe end. Dissimilar metal weld between nozzle and safe end is followed by similar metal weld between safe end and pipe. And thus residual stress in dissimilar metal weld can be affected by similar metal weld. Similar metal weld impose bending stress on dissimilar metal weld, which is according to the length of safe end. In this study, simple nozzle model which covers various radius to thickness ratios was proposed to quantify residual stress in dissimilar metal weld based on finite element analyses. As a result, short length of safe end was proved to be more effective to mitigate residual stress in dissimilar metal weld and critical effective length of safe end is provided according to the radius to thickness ratio.
https://doi.org/10.3795/KSME-A.2009.33.7.664 인용 PDF KSCI

Bae, H.Y.;Song, T.K.;Chun, Y.B.;Oh, C.Y.;Kim, Y.J.;Lee, K.S.;Park, C.Y.
- Proceedings of the KSME Conference
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- 2008.11a
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- pp.88-93
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- 2008
Weld overlay is one of the residual stress mitigation method which arrest crack. An overlay weld sued in this manner is termed a preemptive weld overlay(PWOL). PWOL was good for distribution of residual stress of dissimilar metal weld(DMW) by previous research. Because range of overlay welding is wide relatively, residual stress distribution on PWR is affected by welding sequence. In order to examine the effect of welding sequence, PWOL was applied to a specific DMW of KORI nuclear power plant by finite element analysis method. As a result, the welding direction that from nozzle to pipe is better good for residual stress distribution on PWR.
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Park, June-Soo;Song, Min-Seop;Kim, Jong-Soo;Kim, In-Yong;Yang, Jun-Seog
- Proceedings of the KWS Conference
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- 2009.11a
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- pp.100-100
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- 2009
This paper is concerned with numerical analyses of residual stresses in welds and material's susceptibility to stress corrosion cracking (SCC) for the primary piping system in nuclear power plants: Both the dissimilar metal weld (DMW) for stainless steel to low alloy steel joints and the similar metal weld (SMW) for forged stainless steel to cast stainless steel joints are considered. Thermal elasto-plastic analyses using the finite element method (FEM) are performed to predict residual stresses generated in fabrication welding and its related processes for both the DMW and SMW, including effects of quenching for cast stainless steel piping, machining of the DMW root, and grinding of the SMW root. As a result, the effect of quenching should be included in the evaluation of residual stresses in the SMW for the cast stainless steel piping. It is deemed that residual stresses in both the DMW and SMW would not affect the SCC susceptibility of the welds providing that the welding processes are completed without any weld repair on the inside wall of the joint. However, the grinding process if performed on the safe-end to piping weld, would produce a high level of residual stresses in the inner surface region and thus a stress improvement process (e.g. buffing) should be considered to reduce susceptibilities to SCC.
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