• Proceedings of the KWS Conference
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• 1998.10a
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• pp.129-132
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• 1998

The dynamic resistance monitoring in primary circuit or T/C is one of the important issues in that in-process and real time quality assurance of resistance spot weld is needed to increase the product reliability. It is well known that tile dynamic resistance curve gives us very useful information about nugget growth and weldability. In the present paper, a new dynamic resistance detecting method is presented as a practical manner of weld quality assurance using instantaneous current and voltage measured by primary circuit. Primary dynamic resistance patterns are basically similar to those of the secondary, but there is evident advantage such as no extra devices are needed to obtain the quality assurance index and eventually feedback control will be possible caused by T/C based monitoring system.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.4-4
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• 2009

Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) was welded through a combination of a diode laser and CNC. Laser beam passed the transparent PC and was absorbed in an opaque ABS. Polymers were melted and welded by absorbed and conducted heat. Experiments were carried out by varying working distance from 44mm to 50mm for the focus spot diameter control, laser input power from 10W to 25W, and scanning speed from 100 to 400mm/min. The weld bead size and the specimen cross-section were analyzed, and tensile results were presented through the joint force measurement. With focus distance at 48mm, laser power with 20W, and welding speed at 300mm/min, experimental results showed the best welding quality which bead size was 3.75mm and the shear strength was $22.8N/mm^2$. Considering tensile strength of ABS is $43N/mm^2$, shear strength was sufficient to hold two materials. A single process was possible in CNC machining processes, surface processing, hole machining and welding. As a result, the process cycle time was reduced to 25%. Compared to a typical process, specimens were fabricated in a single process, with high precision. By combining two operations processes developed process gained 50% more efficiency.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.49-54
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• 2015

Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.1-12
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• 1993

용접과 관련되는 분야에서, 재료평가와 비파괴 검사법으로서의 Acoustic Emission의 응용을 살펴 보았다. 재료 평가법으로서의 AE는 다른 시험방법들이 검출해 내지 못하는 재료 내부에서의 미시적인 현상들을 정량적으로 평가할 수 있는 장점을 가지고 있다. 앞으로 새로운 용접재료의 개발이라든지, 고도의 신뢰성이 요구되는 용접부위의 정량적인 평가를 위해서 AE의 응용은 중요한 정보들을 제공하게 될 것이다. 한편 용접구조물의 비파괴적 평가법으로서의 AE는 균열의 동적인 거동 및 균열의 위치를 검지할 수 있다는 장점 때문에 응용범위는 더욱 넓어질 것이다. 여기서 유의하여야 할 점은, 목적으로 하는 AE신호를 수만배 까지 증폭시키는 과정에서 환경잡음의 영향을 무시할 수 없는 경우에는 우선적으로 잡음을 적극적으로 제거하는 고도의 연구도 함께 병행되어야 한다는 것이다.

• Journal of Environmental Health Sciences
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• v.33 no.6
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• pp.506-512
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• 2007

This study was conducted to describe the exposure levels of welding fumes by the type of manufacturers, work process, welding type and the size of manufacturers, and to find out the trend of chronological changes of airborne welding fume levels. The subjects of this study were 509 manufacturers, consisting of 11 types of manufacturers, 3 work processes, 7 welding types, in Busan from January, 1997 to December, 2005. Airborne concentration of welding fume was determined by manual of National Institute for Occupational Safety and Health (NIOSH), and the data were analyzed by using SPSS 10.0 for Windows program. The mean concentration of airborne welding fume in all manufacturers was $1.29\;mg/m^3$ (Range: $0.01{\sim}3.00\;mg/m^3)$. The level of welding fume was the highest, as $1.96\;mg/m^3$, for manufactures of motor vehicles, trailers and semi-trailers, which was lower than $5.0\;mg/m^3$ of 8 hr-TWA in Korean permissible exposure limit for welding fume. There was a significant difference in the mean levels of welding fumes by work process, showing the highest in welding workshop ($1.39\;mg/m^3$), followed by pipeline welding workshop ($1.26\;mg/m^3$) and engineering workshop ($1.20\;mg/m^3$). Among welding types, the mean level of welding fume was the highest in the type of $CO_2$ & arc welding, as $1.46\;mg/m^3$, followed by $CO_2$ welding ($1.40\;mg/m^3$), shielded metal arc welding ($1.31\;mg/m^3$), spot welding ($1.27\;mg/m^3$), and so on. The highest mean level of welding fume was $1.58\;mg/m^3$ in work process of pipe line welding workshop for the manufacturers of basic iron and steel, and $2.27\;mg/m^3$ in the type of arc welding for the manufactures building ship and boats. By the size of manufacturers, the mean concentration of welding fume for manufactures in small scale with less than 50 workers was the highest as $1.45\;mg/m^3$ (Range: $0.07{\sim}3.00\;mg/m^3)$. The mean level of welding fume was the highest as $1.39\;mg/m^3$ both in 1997 and in 2005, showing a trend of fluctuating periodically within a range of $1.10{\sim}1.39\;mg/m^3$. The above results suggested that more effective control program for work environment producing welding fumes should be developed and applied since there were significant variations in welding fume levels by the type of manufacturers, work processes, welding types, the size of manufactures, and by year.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.1
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• pp.90-96
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• 2011

The shock absorber base assembly is one of the parts in the shock absorber equipment that controls the vehicle movement. It absorbs the shock and vibration to guarantee riding stability and comfort. It demands strength, reliability and strict airtightness of the welded section because the shock absorber base assembly is a container which resists pressure and needs durability by being filled with gas and oil. However, the current engineering needs a lot of production time, has a high cost and shows a low production rate. These problem due to the eight production processes, four of which are spot welding, reinforcement welding like metal active welding (MAG), prior process of the base assembly cap and tube for precision and pressing. We will analyze the manufacturing processes of the base assembly and suggest an improved manufacturing method that uses frictional welding. The results will show that the new method of the frictional welding is better than the previous welding technique. Through the use of this concept of frictional welding, the welding conjunction will be strengthened, measurements will be more precise, and the cost and the number of processes will be reduced.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.29-29
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• 2009

On this research, laser welding technology for manufacturing automobile body is studied. Laser welding technology is one of the important technologies used in the manufacturing of lighter, safer automotive bodies at a high level of productivity; the leading automotive manufacturers have replaced spot welding with laser welding in the process of car body assembly. Korean auto manufacturers are developing and applying the laser welding technology using a high output power Nd:YAG laser and a 6-axes industrial robot. On the other hand, the robot-based remote laser welding system was equipped with a long focal laser scanner system in robotic end effect. Laser system, robot system, and scanner system are used for realizing the high speed laser welding system. The remote laser welding system and industrial robotic system are used to consist of robot-based remote laser welding system. The robot-based remote laser welding system is flexible and able to improve laser welding speed compared with traditional welding as spot welding and laser welding. The robot-based remote laser systems used in this study were Trumpf's 4kW Nd:YAG laser (HL4006D) and IPG's 1.6kW Fiber laser (YLR-1600), while the robot systems were of ABB's IRB6400R (payload:120kg) and Hyundai Heavy Industry's HX130-02 (payload:130kg). In addition, a study of quality evaluation and monitoring technology for the remote laser welding was conducted. The welding joints of steel plate and steel plate coated with zinc were butt and lapped joints. The quality testing of the laser welding was conducted by observing the shape of the beads on the plate and the cross-section of the welded parts, analyzing the results of mechanical tension test, and monitoring the plasma intensity and temperature by using UV and IR detectors. Over the past years, Trumf's 4kW Nd:YAG laser and ABB's IRB6400R robot system was used. Nowadays, the new laser source, robot and laser scanner system are used to increase the processing speed and to improve the efficiency of processes. This paper proposes the robot-based remote laser welding system as a means of resolving the limited welding speed and accuracy of conventional laser welding systems.

• Journal of Welding and Joining
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• v.27 no.4
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• pp.73-78
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• 2009

Characterization of the microweld CCFL electrode for the TFT-LCD backlight unit was carried out in terms of the glass beading heat treatment conditions. We evaluate the weld zone and parent metal of the microweld CCFL electrodes that were exposed to simulated glass beading heat treatment. The CCFL electrode was composed of the cup made with pure Ni, the pin made with pure Mo and the lead wire made with Ni-Mn alloy. Each part of the electrode was assembled together by micro spot welding process and then the assembled electrodes were exposed to simulated glass beading temperatures of $700^{\circ}C,\;750^{\circ}C$ and $800^{\circ}C$. The microstructures of the microweld CCFL electrode were observed by using optical microscope, scanning electron microscope and EDS. Micro-tensile and microhardness test were also carried out. The results indicated that the grain coarsening in the HAZs(heat affected zones) for both the cup-pin weld and pin-lead wire were exhibited and the grain coarsening of the HAZ for the cup and the lead wire was more obvious than the HAZ of the pin. The micro-tensile test revealed that the fracture occurred at the cup-pin weld zone for all test conditions. The fracture surface could be classified into two parts such as pin portion and cup portion including weld nugget. The failure was seemed to be initiated from the boundary between nugget and pin through the weld joint. The result of the microhardness measurement exhibited that the relatively low hardness value, about 105HV was recorded at the HAZ of the cup. This value was about 50% less than that of the original value of the cup. The reduction of the microhardness was considered as the cause of the grain coarsening due to welding process. It was also appeared that there was no change in electric resistance for the standard electrodes and heat treated electrodes.

• Journal of Welding and Joining
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• v.26 no.1
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• pp.69-75
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• 2008

Spot welding which use the main process for side block production of stainless steel railway vehicle is legged behind in laser welding about a quality and productivity. Although the laser welding has many potential advantages such as low heat input and aspect ratio of weld bead, its application to a new structural component still is required many engineering data including mechanical properties such as tensile, fatigue strength, etc on. Therefore, experimental analysis was carried out to understand the fatigue phenomena of different thickness stainless steel overlap joining panels by Nd:YAG laser welding. The fatigue life curves were obtained through fatigue tests with the various levels of applied load. The fatigue life is related with the parameters such as gap size and penetration depth through experiment. As the results, tensile strength and fatigue life were proportional in heat input level and gap was identified the major factor for fatigue life. Also we could know that deferent a-ferrite content at HAZ depend on welding heat input was important factor to determine a formation of initial crack and total fatigue life cycle.

• Laser Solutions
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• v.12 no.3
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• pp.14-17
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• 2009

The laser welding was performed for the flange joint of two overlapped coaxial circular pipes which serve as the inlet and connector pipes of STS 316L. The laser welding test finally resulted in a good penetration depth of 1.8 to 2.0 mm. On the way to get the good welding quality, two important parameters were found to be optimized. One is the focal positioning which is the offset of the laser beam focus to the exact welding seam line, which is more critical in the inner flange laser welding. When the beam spot size was deviated more than $200\;{\mu}m$ from the seam line, welding of two pipes is failed. The other is a gap size since a certain amount of gap is inevitable due to fabrication tolerance, or artificial allowances for smooth insertion of a pipe. However, it is required to restrict the gap allowance within 0.2mm to avoid undesirable undercut on a welding bead.