Al6061-T6 판재의 마찰교반용접 3D 유한요소 해석

구병춘,정현승,Goo, Byeong-Choon,Jung, Hyun-Seung 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.4

Friction stir welding (FSW) is a solid state joining method patented in 1991 by The Welding Institute (TWI). It is widely used for joining light metals such as Al and Mg alloys. Foreign railway vehicle manufacturing companies have been applying FSW to car body welding, but domestic companies are in the beginning of feasibility study. Therefore, lots of experimental and analytical study is needed. In this study, three-dimensional finite element modeling of the friction stir welding of two Al6061-T6 plates was carried out. And temperature field and residual stresses were obtained and compared to experimental results in the literature. It is found the analytic thermal field is in a good agreement with the experimental results, but there are some differences between numerical and experimental residual stresses.

계장화 압입시험에 의한 용접부의 물성 측정 및 피로수명 예측

구병춘,이동형,권동일,최열,Goo, Byeong-Choon,Lee, Dong-Hyung,Kwon, Dong-Il,Choi, Yeol 한국철도학회 2004 한국철도학회논문집 Vol.7 No.2

When material properties depend much on positions in a material or it is difficult to make test specimens from a material or component, an instrumented indentation test described in ISO 14577-1, 14577-2 or KS B 0950 can be used to measure material properties and damage. In this study, first of all, the principals of the instrumented indentation test, KS B 0950 are introduced and yield strengths, tensile strengths and work hardening exponents of base materials, heat affected zones and weld materials are measured. In addition, the influence of post-weld heat treatment on the material properties is investigated. Finally the fatigue lift of butt welded specimens are evaluated by the local strain approach. To calculate local strains and stresses, elasto-plastic finite element analysis is conducted using the measured properties.

용접부의 피로강도 시험평가 및 해외규격과의 비교연구

구병춘,김재훈,Goo, Byeong-Choon,Kim, Jai-Hoon 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.1

A lot of fatigue tests on a material, JIS SM490A, with yielding strength of about 350 MPa and tensile strength of about 520 MPa were carried out. Various butt-welded specimens such as reinforcement removed, as-welded and weld toe ground, several types of fillet-welded specimens and full-size box type components were used. After having obtained S-N curves for the above- mentioned specimens, fatigue strengths were compared to those of foreign design codes, AWS, BS 7608 and ENV. It was found the fatigue strengths at low cycles are not in a good agreement with the foreign codes, but the fatigue limits are in a good agreement.

철도차량 구조물의 피로강도에 관한 실험적 연구

구병춘(Goo Byeong-choon),김재훈(Kim Jae-Hoon),오창록(Oh Chang-rok),김대진(Kim Dae-Jin) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-

We investigated the effect of weld details on fatigue behavior of a material, JIS SM 490 A, with yielding strength of about 350 ㎫ and tensile strength of about 520 ㎫. Tensile tests, instrumented indentation tests and fatigue tests were carried out on double V-grooved butt weld plates such as reinforcement removed, as-welded and weld toe ground. In addition plates with transverse fillet welded web, load carrying cruciform fillet welded plates, non-load-carrying cruciform fillet welded plates, longitudinal butt welded plates and welded rectangular life-size box beams were tested. S-N curves for the above specimens were obtained and analyzed.

파괴역학을 이용한 차륜과 레일의 마모에 관한 연구

구병춘(Goo Byeong-Choon) 한국철도학회 1998 한국철도학회 학술발표대회논문집 Vol.- No.-

A two dimensional elasto-plastic finite element program taking into account contact between crack surfaces is developed in order to analyze subsurface cracking in rolling contact. But the friction between upper and lower surface of the crack is not considered. Under the assumptions of small deformation and small displacement, the incremental theory of plasticity is used to describe plastic deformation. J-integral is computed as the applied Hertzian load slides over the surface with friction. J-integral is correlated with wear rate of the rail. The propagation rate of the right tip of the subsurface crack is fast by 45% than that of the left side.

철도차량 구조물의 대기부식 및 피로에 관한 연구

구병춘(Goo Byeong-Choon),김재훈(Kim Jai-Hoon),장세기(Jang Se-Ky) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-

In general, structural integrity of rolling stock structures should last more than 25 years. During the lifetime corrosive degradation occurs. For structural design and diagnosis, quantitative relationship between corrosive degradation and variation of mechanical properties such as tensile strength and fatigue strength is needed. In this study, first of all we established the atmospheric corrosion test procedure. At regular intervals using specimens of SM490A and SS400 on the atmospheric corrosion test bed, we carried out tensile and fatigue tests. The fatigue strength decreases as the atmospheric corrosion period increases. And we studied the effect of post-weld heat treatment on the tensile and fatigue behaviour.

고마찰 동계 소결 마찰재 개발

구병춘(Byeong-Choon Goo) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.3

유한요소법에 의한 휠/레일 스킬소음 해석

구병춘(Byeong-Choon Goo) 한국철도학회 2015 한국철도학회 학술발표대회논문집 Vol.2015 No.5

국부변형률법과 독자모델에 의한 용접부 피로수명 평가

구병춘(Byeong Choon Goo),양승용(Sung Yong Yang),서정원(Jung Won Seo),정흥채(Hung Chai Jung) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8

To evaluate the fatigue lives of welded joints taking into residual stress relaxation, two approaches are applied. One is based on the conventional local strain analyses. The other is based on a model developed by the authors. In the first approach, the Ramberg-Osgood relation, Lawrence model and S.W.T. parameter are used. In the second approach, The S-N curve for a welded joint is deduced from that of the parent material corresponding to the welded joint. Residual stress relaxation obtained by finite element analysis is considered. Finally, we evaluate the fatigue lives of butt welded plates and plates with transverse filet welded rib using the two approaches.

C/C-CrSi₂-Si 복합재 마찰 · 마모 특성 연구

구병춘(Byeong-Choon Goo) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.10

탄소 기지와 탄소 섬유로 이루어진 탄소/탄소 (C/C) 복합재와 Si를 함침한 C/C-SiC 복합재는 가볍고, 내열성과 내마모성이 우수하여 항공기, 자동차의 제동 마찰재, 클러치 등에서 전통적인 마찰재를 대체하는 신소재로 사용되고 있다. 탄소/탄소 복합재의 성능을 향상하기 위해 Si 외에, Cu, Ti, Zr, B 등 여러 원소를 첨가한 복합재가 개발되고 있다. 본 연구에서는 우선 탄소 섬유와 페놀 레진을 섞어 혼합물을 만들어 이 혼합물을 170 ℃까지 가열하여 이 온도에서 30분 동안 유지하여 복합재 전구체를 제작하였다. 탄소/탄소 복합재를 만들기 위해 이 혼합물을 불활성 가스 분위기에서 10 ℃/min의 속도로 1,000 ℃까지 가열한 후 2,000 ℃에서 열처리 하였다. 마지막으로 이 복합재 표면에 CrSi2와 Si 분말을 놓고 1,550 ℃까지 가열하여 분말이 용해되어 함침되게 하여 C/C-CrSi₂-Si 복합재를 제작하고 여러 종류의 시편을 채취하여 특성을 평가하였다. 주사전자현미경과 에너지 분산 X-선 분광기를 이용하여 조직과 성분을 분석하였다. 복합재의 인장강도는 약 10 MPa, 항복강도는 26 MPa 정도였다. 횡방향과 수직방향의 열전도도는 25 ℃에서 각각 85.2와 30.7 W/m-K로 C/C-SiC에 비해 더 큰 값을 보였다. CrMoV 합금을 상대재로 하고 C/C-SiC, C/S-SiC-Cu, C/C-CrSi₂-Si 세 종류의 탄소/탄소 복합재 시편을 사용하여 미끄럼마모 시험을 하였다. 마찰계수는 C/C-SiC, C/S-SiC-Cu, C/C-CrSi₂-Si 순서로 작고, 마찰면에는 응착마모와 연삭마모가 관찰되었다. Carbon/carbon (C/C) composites have been used as new friction materials for aerospace, automobiles, and clutches because they are light and have good friction and wear characteristics at high temperatures. Other additive elements, such as Si, Cu, Ti, Zr, and B, are added to produce new C/C-based composites to improve the tribological properties of C/C composites. In this study, C/C composites were produced using carbon fibers and resin. Chopped carbon fibers were mixed with a phenol resin powder. The mixture was heated to 170 ℃ for 30 minutes. The C/C composites were obtained by heating the mixture to 1,000 ℃ at 10 ℃/min in an inert gas, followed by heat-treatment at 2,000 ℃. Finally, the C/C composite was infiltrated with molten CrSi₂ and Si at 1,550 ℃. Several specimens were extracted from C/C-CrSi₂-Si composites. Scanning electron microscopy and energy dispersive spectroscopy analysis were conducted. The tensile and bending strengths were approximately 10 MPa, and 26 MPa, respectively. The heat transfer coefficients in the transverse and vertical directions were 85.2 and 30.7 W/m-K at 25 ℃, respectively. Compared to the C/C-SiC composite, the heat transfer coefficient was significantly high. Sliding friction and wear tests were conducted using a CrMoV alloy from a KTX brake disc as a mating counterpart. The test results were compared with those of the C/C-SiC and C/S-SiC-Cu composites. A microscopic examination of the friction surface showed that adhesive wear and abrasive wear occur together.