• 한국공작기계학회논문집
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• 제16권1호
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• pp.9-18
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• 2007

There have been continuous efforts for automation of joint tracking system. This automation process is mainly used to do in root pass of gas metal arc welding in the field of heavy industry and shipbuilding etc. For automation, it is important using of vision sensor. Welding robot with vision sensor is used for weld seam tracking on welding fabrication. Recently, it is used to on post-weld inspection for weld quality evaluation. For real time seam tracking, it is very important role in vision process technique. Vision process is included in filtering and thinning, segmentation processing, feature extraction and recognition. In this paper, it has shown performance comparison results of seam tracking for real time root pass on gas metal arc welding. It can be concluded better segment splitting method than iterative averaging technique in the performance results of seam tracking.

• Journal of Welding and Joining
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• 제19권6호
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• pp.636-642
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• 2001

Partial penetration welding joint defines the groove welds that applies the one side welding which does not use steel backing and both side welding without back gouging, that is, the partial penetration welding joint leaves an unwelded portion at the root of the welding area. In this study, we analyzed the residual stress and fracture on the thick metal plates that introduced the partial penetration welding method. As results of using above mentioned welding method, we could draw a conclusion that longitudinal stress and traverse stress occurred around the welding area was so minimal and did not affect any influence. We also performed the fracture behavior evaluation on the partial penetration multi-pass welding with 25.4mm thick plate by using theJ-integral, which finally led us the conclusion that the partial penetration multi -pass welding method is more applicable and effective in handling the root face with less than 6.35mm.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1813-1819
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• 2001

Partial penetration welding Joint defines that groove welds without steel backing, welded from on side, and groove weeds welded from both sides but without back gouging, that is. it has an unwelded portion at the root of the weld. In this study we analysed fur residual stress and displacement distribution on partial penetration welding condition of thick plate metal. For 25.4mm thick plate, theoretical residual stress and displacement analysis by finite element method using ABAQUS was carried out and compared with the experimental result using hole-drilling method. In results of the condition of partial penetration, it appeared that longitudinal stress at welding area was a little difference and transverse stress did not have any effect by partial penetration multi-pass welding. From a point of welding distortion in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• Journal of Welding and Joining
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• 제17권5호
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• pp.47-54
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• 1999

It is well known that solidification cracking often occurs in welds of root pass for one-side welding under the conditions of high welding currents and speeds. In this study, the solidification in 590MPa class steel for pressure vessels SPPV490 was investigated by using flux-cored arc welding(FCAW) with 4 types of welding wires and welding conditions of 200∼280A and 2.8∼ 4.2mm/sec. In order to compared the result of cracking in SPPV490, 0.2%C steel for welded structure of SWS400 and 0.45%C steel for machine structural SM45C were also used as base metals. As the results, all the cracks formed in some welding conditions were observed near the center of weld bead. The solidification cracks were generally initiated near the upper surface of bead and propagated toward the inner part. The solidification cracking generally increased with welding current and welding speed in the same base metal and welding material. In cracking susceptibility, SPPV490 showed higher cracking susceptibility than SWS400 in all welding conditions and welding materials. It was considered that cracking susceptibility could not be evaluated with the hardness of weld metals. The cracking ratio increased with decreasing of a/b(a and b; the width of the upper surface and the back surface of the bead) as shape factor of bead. The cracking tendency with shape factor of bead was extended under the condition of higher welding currents.

• 한국생산제조학회지
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• 제20권1호
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• pp.74-80
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• 2011

In this study, a variety of welding experiments were carried out to optimize root-pass welding process using GMA process. Based on the experimental results, optimal welding conditions were selected after analyzing correlation between welding parameters and back-bead geometry. Then, effectiveness of empirical models developed was compared and analyzed, and optimized empirical models were finally developed for predicting back-bead by analyzing the main effect of each factor which affects back-bead geometry and their influence on interaction. Also, functions proper for expressing the surface of back-bead were selected using diverse quadratic functions, and back-bead geometry was visualized using empirical models developed and quadratic functions.

• 대한조선학회논문집
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• 제39권3호
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• pp.81-88
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• 2002

용접구조물의 루트부는 외력에 의한 응력 집중에 의해 파손되기 쉽다. 따라서 구조물의 안전성 및 신뢰성 측면에서 홈 가공한 그루브 용접에 의한 완전용입 용접이 일반적으로 요구되어진다. 하지만 필릿 T-이음부 용접은 루트부의 갭과 같은 불완전 용입부를 만들어내기 쉬움에도 불구하고 홈 가공 시간 및 용접봉 소모량을 줄이기 위해 이러한 필릿용접이 자주 행해지고 있다. 따라서, 본 연구에서는 필릿 용접구조물의 플래이트(또는 플랜지)와 웨브 부분에 발생하는 용접잔류 응력과, 특히 불완전 용입에 의한 루트부 갭을 갖는 양면 T-이음부의 노치부분에 발생하는 잔류응력 분포를 해석하고자 하였다. 해석을 위해서 서브머지드 아-크 용접에 의한 단층 및 다층패스용접 모델을 선정하였으며, 열전도 및 열탄소성 이론을 고려한 유한요소 프로그램을 사용하였다.

• 대한기계학회논문집A
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• 제41권4호
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• pp.321-327
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• 2017

본 연구에서는 수평 자세에서의 TIG 용접 시 반응표면법(RSM)을 이용하여, 최적의 이면비드 형상을 구하는 연구를 진행하였다. 입력변수로는 베이스 전류, 피크 전류, 용접속도를 선정하였고, 이면비드 폭을 용접품질에 관한 출력변수로 하여 목표값을 5.4 mm로 설정하였다. Box-Behnken 실험계획법에 따라 실험을 진행하였고, 비드 폭에 관한 2차 회귀모형을 구한 후, F-테스트를 이용하여 회귀모델을 검정하였다. 그리고 망목특성의 호감도 함수를 사용하여 이면비드 형상을 평가함으로써 최적화를 수행하였다. 이렇게 도출된 최적의 용접조건은 코드화된 값으로 베이스 전류; 0.9204, 피크 전류; 0.8676, 용접속도; 0.3776이었다. 검증실험 결과 목표값에 근접한 5.38 mm의 이면비드 폭을 얻을 수 있었다.

• 대한기계학회논문집A
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• 제26권2호
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• pp.300-307
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• 2002

Partial penetration welding joint is defined as groove welds welded from one side, without steel backing or groove welds welded from both sides but without back gouging. So it has an unwelded portion at the root of the weld. Study of partial penetration weldment fracture behavior includes residual stress analysis and fracture analysis. The J-integral loses its path independency in residual stress field. Therefore, it is necessary to introduce a new J-integral, J, which is defined including the effect of plastic deformation and thermal strain. In this study, theoretical formulation and program were developed for the evaluation of J-integral for the crack tip located in the weldment. Evaluations of fracture behavior were performed for partial penetration multi-pass weldment of 25.4mm thick plate by J-integral. From a point of fracture in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• Journal of Welding and Joining
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• 제7권4호
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• pp.22-29
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• 1989

In this paper weld distortion both in butt and fillet welds by flux cored arc welding has been investigated by changing welding parameters such as heat input and plate thickness, and the weld distortion was expressed as a function of welding parameters adopting the inherent strain theory as proposed by Watanabe and Satoh in 1961. As results of the research it is proposed that transverse shrinkage in root pass butt welds in proportional to ln[(Q/t_-tan.theta.] where Q is heat input(cal/mm), t is plate thickness(mm), and 2.theta. is groove angle(degree), and angular distortion .phi.(radian) in one pass of fillet welds has the following relationship: .phi..var.(Q/ $t^{1.5}$)$^{3}$exp[-(Q/ $t^{1.5}$ )$^{2}$3/] These equations provide us with basic tools to predict the amount of weld distortion in welded structures.

• 한국강구조학회 논문집
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• 제10권4호통권37호
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• pp.709-720
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• 1998

용접잔류응력의 모재두께방향을 포함하는 3차원 분포를 파악하기 위해, 용접상세를 변화시킨 필렛용접이음을 대상으로 해서 실험 및 해석을 수행하였다. 특히, 지금까지 계측이 곤란했던 필렛용접이음의 용접루트부의 잔류응력을 실측하였다. 파라메타로써는 용접입열량과 용접층수를 취급하고, 모재두께방향을 포함하는 3차원 잔류응력의 분포를 조사하였다. 그 결과, 입열량이 증가하면, 용접토우와 루트부를 포함하는 용접부에서는 잔류응력의 크기에 변화가 거의 없지만, 인장잔류응력의 영역이 크게 나타났다. 또 단층과 다층용접의 비교에서는, 다층용접 쪽이 단층용접보다 잔류응력이 상당히 낮음을 알 수 있었다. 용접부 근방의 인장잔류응력의 영역도 다층용접 쪽이 단층용접보다 작게 나타난 것을 알 수 있었다.