• 한국레이저가공학회지
• /
• 제17권2호
• /
• pp.11-18
• /
• 2014

This research was conducted as a fundamental study to apply tailored blank welding technique into automotive production process. Specially we tried to apply the TWB technique to exhaust system. The materials used in this work were ferritic 439 stainless steel sheet with a thickness of 1.2mm and 0.8mm. Welding tests were conducted for BOP test and dissimilar thickness (0.8 to 1.2t) cases. Major process parameters were position of focus, travel speed, shielding gas and joint (gap) condition. As a result, there are nothing significant welding characteristic compare with TWB of carbon steel. Stainless steel shows the good weldability and mechanical properties (tensile, hardness and forming strength) also shows high level. Just problem is gap condition. However, also in this case, it shows not only good forming strength but also base metal fracture after tensile test. And to conclude, it is good opportunity to make lightweight design muffler using TB welding technique.

• Journal of Welding and Joining
• /
• 제24권5호
• /
• pp.49-56
• /
• 2006

For laser welding in shipbuilding industry, gap bridging capability is one of the most important characteristics to achieve the high productivity and good weld quality. Recently, laser-GMA hybrid welding process is regarded as a distinctive method to overcome the tight gap tolerance with improving the productivity. In this study, the influence of process parameters on the bead formation was experimentally analyzed and the relationship between the process parameters and geometric imperfections was investigated. It was revealed that undercut, excessive weld metal, excessive penetration and incompletely filled groove were the major geometric imperfections. The optimized wire feeding and arc pressure were necessary to ensure the gap bridging ability. The approach to select the process parameters was conducted for butt welding with up to 2mm joint gap, in which the sound weld beads were generated without changing the welding speed.

• 한국정밀공학회지
• /
• 제21권4호
• /
• pp.161-169
• /
• 2004

In this study, we investigated fatigue crack growth behavior of laser welded sheet metal due to a single overload. Fatigue specimens were made using butt joint of cold rolled sheet metal that was welded by $CO_2$ laser. The fatigue crack propagation tests were performed in such a way that fatigue loading was parallel to the weld line while crack propagation was perpendicular to the weld line. Single overload was applied when fatigue crack tip was arrived near the weld line. The distances between the crack tip and the weld line at which a single overload was applied were 6, 4 and 2mm. The effect of specimen thickness and overload ratio on the fatigue behavior was determined. The plastic zone size of crack tip due to the single overload was determined from the finite element analysis. For investigating fatigue crack growth behavior, we used different thickness specimen 0.9mm and 2.0mm, and variable overload ratio applied fatigue crack propagation test. Also we used finite element analysis for investigating the plastic zone size of crack tip when single overload applied

• Journal of Welding and Joining
• /
• 제13권4호
• /
• pp.122-131
• /
• 1995

An automatic welding equipment for thick plates requires the capability of the seam tracking of the weld line which often includes misalignment of the workpiece and variation of groove width. In this study, an automatic welding equipment and control algorithms based on the arc sensor were proposed for the GMA welding of thick plates which had misalignment and gap variation. The developed system being constituted with 5 axis can be automatically controlled by computer and also automnatically set the welding conditions such as welding current, and voltage. The proposed algorithms for the seam tracking in multi-pass welding of the thick plates were constituted as follows : the detection of weaving-end point for findng the variation of groove width, the control of welding velocity for acquiring a constant thickness deposition of weld metal, and the calculation of groove width and height of an arbitrary pass in the multi-pass weld. As results of the application of the system, it was revealed that the system had a good capability in seam tracking and made an excellent weld quality in V groove butt joint.

• 한국해양공학회지
• /
• 제24권6호
• /
• pp.92-96
• /
• 2010

Recently, the application of aluminum alloys has been increasing for lightweight and high quality transport vehicles. Therefore, the proposal has been made to apply high speed hybrid welding methods to the marine grade aluminum alloy (A5052) used for shipbuilding by combining a 3-KW CW Nd : YAG laser and the MIG welding process. In this study, the characteristics of the welding parameters were investigated for a hybrid butt joint. This paper also describes the determination of the heat distribution in a weldment and the welding residual stress using a finite element method. Mechanical experimentation was also used to ascertain the reliability of the weldment.

• 한국가구학회지
• /
• 제26권4호
• /
• pp.409-420
• /
• 2015

This study intends to explore a teaching philosophy of a Master, a joiner, a cabinet maker, Byeung-Soo Kim who has devoted his entire life on creating and making traditional Korean wood furniture since the elementary school. His teaching method is to make his learners skillful by learning how to make traditional Korean furniture with the traditional technique or joint handmade. They are able to create the furniture in passing through some levels such as a beginning, a middle, a high, and a special class for three years. Each level suggests that the students should study its own joints from laminating, dado, butt, dovetail, mitered, mortise-and-tenon, rabbet, tongue-and-groove and so on. The teaching method is very unique as the technique different and difficult to fine it from other education processes throughout the country.

• 한국기계가공학회지
• /
• 제16권1호
• /
• pp.90-95
• /
• 2017

Recently, smaller and lighter products have become of interest in industry applications that increasingly demand thin plate joints of thickness 1.0 mm or less using friction stir welding. In this study, high frequency spindles that run at 3,500-6,500 rpm are introduced for thin friction stir-welded plates. Weldability tests are performed for the butt-joint method of Al5052-H32 alloy of 1.0 mm thickness under 3,500-6,500 rpm spindle revolution with 250-400 mm/min feed speed. An optical microscope was used to analyze the bid structure of the welded zone and stir zone. The tensile-strength and hardness of the welded zone were then measured.

• Journal of Mechanical Science and Technology
• /
• 제20권3호
• /
• pp.335-344
• /
• 2006

A comprehensive review of through thickness transverse residual stress distributions in a range of as-welded and mechanically bent components made up of a range of steels has been carried out, and simplified generic transverse residual stress profiles for a plate and pipe components have been proposed. The geometries consisted of welded pipe butt joints, T-plate joints, tubular T-joints, tubular Y-joints and a pipe on plate joints as well as cold bent tubes and pipes. The collected data covered a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. Measured residual stress data, normalised with respect to the parent material yield stress, has shown a good linear correlation versus the normalised depth of the region containing the residual stress resulting from the welding or cold-bending process. The proposed simplified generic residual stress profiles based on the mean statistical linear fit of all the data provides a reasonably conservative prediction of the stress intensity factors. Whereas the profiles for the assessment procedures are fixed and case specific, the simple bilinear profiles for the residual stresses obtained by shifting the mean and bending stress from the mean regression line have been proposed and validated.

• 한국산학기술학회논문지
• /
• 제14권4호
• /
• pp.2021-2026
• /
• 2013

냉각법은 용접과 동시에 용접토치로 부터 일정한 거리 떨어져 있는 용접부를 냉각기체를 이용하여 냉각시켜 용접변형을 최소화시키는 기술이다. 냉각기체에 의해 용접부의 온도를 감소시키면 용접부에 발생하는 열응력이 감소되고 그 결과 소성변형이 최소화되어 최종적으로 용접좌굴과 각변형을 방지할 수 있는 기술이다. 이 방법은 용접부 표면을 냉각시키는 방법으로 용접부를 직접 냉각시킴으로서 현장 적용성 면에서 다른 용접변형 방지법 보다 효율적이다. 본 연구에서는 맞대기용접을 대상으로 용접 후면의 냉각조건(폭, 길이)을 변화시켜 열탄소성해석을 실시하여 해석적방법으로 용접 각변형에 미치는 영향을 검토하였다. 그 결과 용접토치와 냉각 선단과의 거리는 25mm, 냉각 길이는 80mm, 냉각 폭은 30mm의 경우가 각변형 저감에 제일 큰 효과가 있었다. 이때 냉각길이는 길면 길수록 각변형을 감소시킨다.

• Journal of Welding and Joining
• /
• 제26권6호
• /
• pp.54-58
• /
• 2008

Laser welding with AZ61 filler wire was carried out to improve formability though reduction of porosity and formation of under fill bead. Optimum welding condition and mechanical properties of butt joint for $400{\times}500{\times}1.3mm$ magnesium sheets were studied. Optimal welding conditions of laser power, welding speed, and defocusing length are 1000W, 3m/min, and 2mm, respectively. Results of tensile test indicated that both tensile strength and elongation of specimens welded with filler wire were improved at room temperature because of reduction of porosity and under-filled bead formation in addition to the precipitation hardening and microstructure refinement by Al-Mn and Mg-Al-Zn precipitates. At elevated temperature of $200{\sim}350^{\circ}C$, fracture location of tensile specimen was shifted from weld metal to base metal, indicating less softening of weld metal than base metal.