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돌출부 성형공정을 고려한 고강도강 돌출저항용접 용접성능에 대한 영향 분석
최완섭(Wansup Choi),하상언(Sangun Ha),이형일(Hyungyil Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Resistance projection welding (RPW), which is a modified procedure of spot welding, is a process to join materials by passing the current through the projection placed on the part of material. RPW has been widely used in the automobile and vessel manufacturing process for neat appearance and fine adjustability of weld part. Despite this compelling usefulness of RPW, studies on the high strength steel RPW process are limited in the literature. Better understanding of the process undergoing in RPW will help to select the welding parameters such as electrode force, welding current, welding time to get good weldment according to the material properties and dimensions. In this research, we use the fully coupled electrical-thermal-mechanical finite element (FE) analysis to characterize the resistance projection welding process combined with stamping process. The dimension and shape of projections in welding materials are determined by punch and die in stamping process. Prior studies on RPW ignored the results residual stress formed around projection in the stamping process. To check the effect of residual stress on RPW, three dimensional FE analysis of RPW combined with stamping process is established by using commercial FE code (Abaqus, 2013). The FE analysis results of RPW with residual stress around the projection are compared with those without residual stress. The effect of contact area and current density variation on RPW is also studied by conducting fully coupled electrical-thermal-mechanical FE analysis.
경골 원위부 골절 치료에서 교합성 골수강내 금속정과 저 접촉성 압박금속판( L D - D C P ) 과의 비교
박영준,최완섭,윤경동,나화엽,고상훈,이영상 대한골절학회 2002 대한골절학회지 Vol.15 No.2
목 적:경골 원위부 골절의 치료에 있어 교합성 골수강내 금속정 고정술과 저 접촉성 압박금속판 고정술을 이용하여 치료한 예를 대상으로 그 결과를 분석하여 효용성을 알아보고 비교하고자 한다.대상 및 방법:1 9 9 8 년 8월부터 2 0 0 1 년 8월까지 교합성 골수강내 금속정과 저 접촉성 압박금속판 고정술로 치료한 경골 원위부 골절 4 3예중 1년이상 추시 관찰 가능하였던 3 8예를 대상으로 하였다. 23예에서 교합성 골수강내 금속정을 사용하였고, 15예에서 저 접촉성 압박금속판을 사용하여 고정하였으며,방사선학적 결과 및 임상적 결과를 비교 분석하였다.결과:골절의 형태는 Robinson 등의 분류에 따르면, 교합성 골수강내 금속정 고정군에서 제 1 형이 1 2예(52.1%) , 제2 a형이 1 1예 ( 4 7 . 8 % ) 이었고, 저 접촉성 압박금속판 고정군에서는 제1형이 4예 (26.7%), 제2 a 형이 8예 (53.4%), 제2 c형이 3예 ( 2 0 . 0 % ) 이었다. 골유합은 교합성 골수강내 금속정 고정군에서 평균1 6 . 2 주, 저 접촉성 압박금속판 고정군에서는 평균 1 2 . 3 주에서 이루어졌으며 기능적 결과는 K l e m m 등의분류에 따라 교합성 골수강내 금속정 고정군에서 만족스러운 결과가 1 8예(78.2%), 저접촉성 압박금속판 고정군에서는 만족스러운 결과가 1 3예( 8 6 . 6 % ) 였다. 합병증으로 교합성 골수강내 금속정 고정군 1예에서 1 0도 외반 변형을 보였고, 저 접촉성 압박금속판 고정군에서는 특별한 것이 없었다.
45세 이하 대퇴골두 무혈성 괴사에 대한 무시멘트성 인공 고관절 전치환술 -최소 5년 이상의 추시 결과-
한창동(Chang Dong Han),최완섭(Whan Sub Choe),이우석(Woo Suk Lee),조재호(Jae Ho Cho) 대한고관절학회 1999 Hip and Pelvis Vol.11 No.1
Cementless primary porous-coated total hip arthroplasties, which were performed upon 36 patients (47 hips) 45 years old and less with a diagnosis of osteonecrosis from January 1988 to December 1993, had a minimum followup of 5 years and a mean followup of 75.8 (60-120)months. Patients were rated using the Harris hip score, and by serial radiographs. The mean Harris hip score increased from 75.8 points preoperatively to 97.0 points at the most recent followup. Using radiographic criteria, 46 stems met the criteria for bone ingrowth and one stem was considered stable with fibrous fixation. None of the acetabular components showed evidence of measurable migration or loosening. The mean extent of linear wear was 1.01 (0-3.60)mm and the mean rate of linear wear was 0.18 (0-0.60)mm/year. Osteolytic lesions were first detected at an average of 51.8 (12-96) months postoperatively and developed in 48.9% of the femurs and in 17.7% of the acetabulums. Polyethylene wear and linear wear rates were significantly correlated with the frequency of the osteolysis, but were not correlated with onset of time or size of it osteolysis. No revisions were performed for aseptic loosening, but 10 hips were revised for excessive wear in the polyethylene liner and progressive osteolysis. Based on this study, we concluded that polyethylene wear and progressive osteolysis remain more serious problem than mechanical failures in the young patients.
프로젝션용접 FE 해석을 통한 재료강도에 따른 적정용접구간 도출
하상언(Sang Un Ha),최완섭(Wan Sub Choi),임성상(Sung Sang Lim),박영도(Yeong Do Park),이형일(Hyungyil Lee) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.2
프로젝션용접이란 국부적인 열발생을 유도해 원하는 위치에 재료를 접합시키는 용접법이다. 돌출부는 스탬핑 공정을 통해 제작되므로 돌출부 주변 잔류응력은 재료에 따라 변한다. 최근 다양한 고강도강의 개발로 재료특성이 저항용접에 미치는 영향에 대한 관심이 높아졌다. 그러나 고강도강의 적정용접구강은 기존의 강과 다르며 이는 많은 용접문제를 유발한다. 이에 본 연구에서는 Abaqus (6.13ver)로 전기-열-응력이 3중 연계된 3차원 프로젝션용접 전산모사를 수행하며 가압력, 전류, 통전시간, 돌출부 높이, 재료강도에 따라 얻은 해석 너깃크기를 토대로 적정 용접변수 구간을 제시한다. 고강도강 중 하나인 DP780강에 대한 실험과 해석 간 너깃크기의 평균오차는 6.8 %이다. The resistance projection welding is a welding method for inducing local heat generation to join a material to a desired position. As the projection is formed through the stamping process, the residual stresses around the projection varies with the material. Recent developments of various high-strength steels have kindled interest in the effect of material properties on resistance welding. However the acceptable welding domain of high-strength steel differs from that of conventional steels, resulting in various welding problem. In this study, we perform a fully coupled electricalthermal-mechanical finite element analyses (FE) of a 3-dimensional resistance projection welding model using Abaqus(6.13ver). The acceptable welding domains are obtained by using nugget size from FE analyses for various welding parameters such as electrode force, current, welding time, height of projection and material strength. For DP780 steel, one of the high-strength steels, the average error of the nugget size between the experiment and the analysis is 6.8 %.
고령의 대퇴골 경부 골절 환자에서 무시멘트 이극성 고관절 반치환술의 평가
한창동 ( Chang Dong Han ),최완섭 ( Wahn Sub Choe ),심동준 ( Dong Joon Shim ) 대한고관절학회 1997 Hip and Pelvis Vol.9 No.2
From January 1988 to March 1995, we performed 66 consecutive cementless bipolar hemiarthroplasties for displaced femoral neck fractures in elderly patients with serious medical illness and evaluated the clinical and radiological results. Only 41 patients (62. l%) were followed-up for more than two years and only 15 patients (22.7%) visited the hospital regularly. The mean age of the patients was 74.3 years (range, 62 to 92 years). Twelve patients were men and 54 were women. The hospital- ization period was less than 3 weeks for 80.3% of patients (mean period, 32.7 days). Walking with partial weight-bearing was begun at the mean of 4.7 days (range, 1-2l days) postoperatively. All patients acquired initial stability of their prostheses. Daily activity of life was excellent or good in 78.0% (32 patients) of the followed-up patients. For patients who visited regularly, Harris hip scores were higher than 80 points in 80.0% (12 patients) and all prostheses had stable fixation by bone ingrowth and no loosening. Acetabular protrusion was not detected. Early or late complications were insignificant. The postoperative mortality rate was 4.5%, and the follow-up mortality rate was 12.2% in the second year, 4.9% in the third year, and 2.4% in the fourth year. Cementless bipolar hemiarthroplasty in elderly patients with displaced femoral neck fracture and high surgical risk showed satisfactory results despite poor bone quality and osteoporosis.