• 비파괴검사학회지
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• 제29권1호
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• pp.43-48
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• 2009

The fatigue crack growth behavior of high strength X80 pipeline steel was investigated with compact tension specimens that crack growth directions were aligned either parallel or normal to the rolling direction of the pipeline. Also, the fatigue crack growth rates for welded joint of X80 pipeline steel were investigated with compact tension specimens that crack growth directions were aligned either parallel or normal to the welding line. The experimental results indicated the fatigue crack growth behavior was markedly different in three zones, weld metal, heat affected zone and base metal of welded joints. There was a trend toward increment in the fatigue life of weld metal and heat affected zone as compared with the X80 pipeline steel.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1999년도 춘계학술발표대회 논문개요집
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• pp.29-32
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• 1999

The material properties of laser welding zone such as strength coefficient, work-hardening exponent, and plastic anisotropic ratio are analytically obtained from those of base metals based on the tensile tests. . The finite element formulation is developed for predicting strain distributions and weld line movements in the forming processes of laser welded blank. The welding zone(WZ) is modelled with the several, narrow finite elements whose material characteristics are based on the experimental results and the analytical equations. In order to show an application of the developed weld element the stamping process of auto-body door inner panel is simulated. FEM predictions are compared and showed good agreements with experimental observations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.36-39
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• 1998

To predict strain distributions and weld line movements in the forming processes of tailored blank sheets, the 2-dimensional finite element formulation is developed. The welding zone is modelled with the several, narrow finite elements. The material properties of weld elements are calculated from those of base metals, based on the experimental evaluation. To verify the finite element formulation developed, the forming process of an autobody door inner panel section is simulated. FEM predictions are compared and showed good agreements with experimental measurements.

• 한국강구조학회 논문집
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• 제12권3호통권46호
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• pp.269-279
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• 2000

차량하중의 증가 및 부식 등에 의해 손상된 강교량 구조물들은 보수 보강이 요구되어진다. 손상부채를 보수 보강하는 방법은 단면결손이 없다는 장점을 가진 용접에 의한 보수방법이 유리하다. 3차원 탄소성해석 결과를 토대로 공용중 보수용접에 의해 생기는 응력과 변형의 거동에 대해 연구하였다. 균열이 있는 부재에 하중만 작용할 경우 과도 응력의 크기는 보수용접균열길이 및 균열깊이가 큰 순으로 크다. $80MPa({\sigma}_y/3)$ 및 $140MPa({\sigma}_a)$의 응력 작용시 보수용접에 의해 발생되는 응력의 크기는 무응력 상태에서 보수용접시 발생되는 응력의 크기와 하중재하에 의해 생긴 응력의 크기의 합과 비슷하다. 응력 작용시 보수용접에 의해 발생되는 용접선방향 인장과도응력 성분은 부재폭에 대한 균열 길이비(1/b)가 커지면 커짐을 알 수 있다. 또한, 응력 작용시 보수용접에 의해 발생되는 용접선 직각방향의 면내수축변위의 크기는 보수용접길이가 긴순으로 크다.

• Journal of Welding and Joining
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• 제14권1호
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• pp.99-106
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• 1996

Development of an automatic TIG welding system incorporating a vision sensor and torch control mechanism leads to an improved welding quality and greater production efficiency. The automatic welding system should be greatly restricted in its size and weight for the LNG(Liquefied Natural Gas) storage tank and also provide a unique torch rotating mechanism which keeps the torch tip in the constant position while the angle is changed continuously to maintain the welding torch substantially perpendicular to the weld line. The developed system is driven by two translation axes X, Z and one rotational axis. A moving line window method is adopted to the image recognition of the corrugated membranes with specular reflection. This method decides original laser stripe patterns in image which is affected by multi-reflection. A self-teaching algorithm, which guides the automatic welding machine with the information provided by the CCD camera without any previous learning of a reference trajectory, was developed for tracking the corrugated membrane of the LNG tank along the weld line.

• 한국정보통신학회논문지
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• 제5권1호
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• pp.144-149
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• 2001

산업현장의 열악한 작업중의 하나인 용접작업을 자동화하기 위한 방법으로 본 논문은 비접촉식 센서인 Fiber Sensor를 이용하여 용접선을 1차적으로 추적하고, 추적한 데이터를 텍스트 파일로 저장함과 통시에 2차적으로 추적한 용접선을 X-Y 로봇의 좌표값으로 다시 출력하여 용접을 하도록 하고 있다. Fiber Sensor를 통하여 읽어 들인 데이터는 Delphi Version 3.0을 이용하여 만들어진 프로그램을 통하여 처리하였고, I/O 입출력은 16 채널의 Relay Actuator 출력과 16 채널의 opto-isolated 입력이 가능한 PC의 ISA슬롯에 직접 삽입하여 사용하는 카드를 통해서 이루어졌다. 본 실험에서 용접선 추적은 직선, 기울기를 가진 직선 및 곡선에 관하여 추적을 행하였고, 추적한 데이터를 토대로 인버터 $CO_2$ 용접기를 사용하여 용접을 행하여 보았다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 추계종합학술대회
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• pp.558-561
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• 2000

산업 현장의 열악한 작업중의 하나인 용접작업을 자동화하기 위한 방법으로 본 논문은 비접촉식 센서인 Fiber Sensor를 이용하여 용접선을 1차적으로 추적하고, 추적한 데이터를 텍스트 파일로 저장함과 동시에 2차적으로 추적한 용접선을 X-Y 로봇의 좌표값으로 다시 출력하여 용접을 하도록 하고 있다 Fiber Sensor를 통하여 읽어 들인 데이터는 Delphi Version 3.0을 이용하여 만들어진 프로그램을 통하여 처리하였고, I/O 입출력은 16 채널의 Relay Actuator 출력과 16 채널의 opto-isolated 입력이 가능한 PC의 ISA 슬롯에 직접 삽입하여 사용하는 카드를 통해서 이루어졌다. 본 실험에서 용접선 추적은 직선, 기울기를 가진 직선 및 곡선에 관하여 추적을 행하였고, 추적한 데이터를 토대로 인버터 CO2용접기를 사용하여 용접을 행하여 보았다.

• Journal of Welding and Joining
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• 제25권6호
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• pp.64-70
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• 2007

Recently, several models to control weld quality, productivity and weld properties in arc welding process have been developed and applied. Also, the applied model to make effective use of the robotic GMA(Gas Metal Arc) welding process should be given a high degree of confidence in predicting the bead dimensions to accomplish the desired mechanical properties of the weldment. In this study, a development of the on-line learning neural network models that investigate interrelationships between welding parameters and bead width as well as apply for the on-line quality control system for the robotic GMA welding process has been carried out. The developed models showed an excellent predicted results comparing with the predicted ability using off-line learning neural network. Also, the system will extend to other welding process and the rule-based expert system which can be incorporated with integration of an optimized system for the robotic welding system.

• 대한기계학회논문집A
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• 제21권1호
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• pp.124-132
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• 1997

This paper describes an experimental and numerical study on growing ductile crack-tip behaviors. The hybrid experimental and numerical method by means of a computer image processign technique, was applied to the analysis of both base metal and weld metal CT specimens. In the weld metal specimen, the initial crack-tip was placed in front of fusion line, and the crack orientation was perpendicular to it. Finite element analysis of crack growth behaviors in both base and weld matal specimens made of A533B Class 1 steel were also performed to examine the effects of weldment on near crack-tip fields. a series of experimental studies on crack-tip behaviors have clearly shown the qualitative effects of material properties, especially a hardening exponent. The experimental and numerical results have also shown that weldment does not affect displacement and strain fields near a crack-tip while a stress field is influenced by the difference between yield stresses of both base and weld metals.

• 한국레이저가공학회지
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• 제8권3호
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• pp.11-19
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• 2005

In automotive industry, light weight vehicle is one of issues because of the air pollution and the protection of environment. Therefore, automotive manufacturers have tried to adopt light materials such as aluminum alloy to production line. Aluminum welding using laser has some advantages high energy density and high productivity. It is very important to understand weld characteristic according to welding condition in order to determine the possibility of application to car body. In this study, Nd:YAG laser welding of 5182 aluminum alloy with filler wire AA5356 was carried out through experimental design according to wire feed rate, laser power and welding speed. Weld bead shape in terms of cross section photo, bead with, height of reinforcement and penetration depth and mechanical property in terms of tensile strength and formability was investigated. Analysis of variation (ANOVA) was performed to know the effect of weld parameter for weldability, laser power was statistically most significance factor of three variables.