• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.102-111
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• 2017

An automobile ball joint is the element for connecting the control arm and the knuckle arm, allowing rotational motion. The ball joint consists of the stud, plug, socket, and seat. These components are assembled through the caulking process that consists of plugging and spinning. In the existing research, the pull-out strength and gap stiffness were calculated, but we did not consider the uncertainties due to the numerical analysis and production. In this study, the uncertainties of material property and tolerance are considered to predict the distributions of pull-out strength and gap stiffness. Also, pull-out strength and gap stiffness are predicted as the a distribution rather than one deterministic value. Furthermore, a robust design applying the Taguchi method is suggested.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.733-734
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• 2010

• Journal of Welding and Joining
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• v.20 no.3
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• pp.122-128
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• 2002

The laser welding in the automotive industries has been used widely for the butt joint of blank sheets rather than the lap joint of automotive body panels. But as a substitute far the spot welding of automotive body panels, the so called three dimensional laser welding will be important far the body panel engineers. Specially the laser welding of body panels with a smooth weld line is applied increasingly, for example, to the side panels. So far, some criteria of the laser weld quality was suggested by in-house regulations or national standards from experiences and/or rule of thumbs. In the manufacturing places, a go or no-go criterion is adopted because of the simplicity or a lack of rational criteria. It is true specially for the selection of the process parameters, which gives the basic causes for the good quality of laser welds. In this study, the effects of joint combination, gap and welding speed on the lap joint $CO_2$ laser welding of two mild steel sheets with different thicknesses are obtained through a $2{\times}3{\times}7$ factorial experiment. The results of the weld quality are statistically analysed using analysis of variance (ANOVA) and compared between two characteristic zones, which are separated by the type of sectional shapes and the level of input energy per volume. The thickness combinations are 0.8mm/1.2mm, 1.2mm/0.8mm of mild steel sheets. The welding speed covers from the deep penetration to the partial penetration. The gap size has three levels of no-gap, 0.16m, and 0.26mm. The bead width, penetration depth and input energy per volume are measured and used as the weld quality criteria.

• Journal of Welding and Joining
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• v.14 no.1
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• pp.82-91
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• 1996

The maximum butt-joint gap size in $CO_2$ laser beam welding of SAPH steel plates with different thicknesses and its bending formability were studied. In the range of the gap size$\geq$0.1mm, the optimal butt welding speed was faster than that of no gap (air gap) condition. This behaviour was independent on the difference of thickness at any combination. Also, the allowable gap size in steel plates with different thicknesses was larger than with same thicknesses. In the range of $T/T_0$(bead shape) $\geq$ 0.8, good bending formability was obtained at any combination of thickness. The formability was improved by reducing the hardness in weld bead using pre-heating process. Finally, FEM result of the laser beam welded underframe with different thicknesses was compared to that of the conventional spot welded underframe.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.510-516
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• 2002

Recently the laser welding technology has been applied increasingly for the automotive bodies. But the lap joint laser welding for 3 dimensional automotive body is new while the butt joint laser welding is well known as the tailored blank technology. In this study, the process window was found for the full penetration welding of the lap joint of the 1mm-thick high strength steel sheets. The limit curves and characteristic curves were suggested to define the boundaries and the contour lines in a space of the welding speed and the gap size. The characteristics of the weld sectional geometry were used to determine the limit curves. They are bead width, penetration depth and sectional area. After the observed data was analysed carefully, it was noticed that there was a transition point at which the sectional shape was changed and the bead area jumped as the welding speed was increased. Also a new concept of 'input energy Per volume' was suggested to distinguish the difference at the transition Point. The difference of sectional areas at the transition point can be related to the dynamic keyhole phenomena.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.950-955
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• 2005

This paper describes an intelligent filler wire feeding device which can control 3- dimensional seam tracking and the filler wire speed by measuring the gap position and the joint gap width in laser welding. By means of visual sensor controlled filling the missing material into the joint gap and 3 dimensional seam tracking, lineup errors from manufacturing tolerances and the repeatability of lineup jigs and weld robot can be balanced and at an even seam quality which avoids weld defects. In this paper, we assessed weld quality in 2mm sheets of A16061 which had various gap width by using the intelligent filler wire feeding device.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.27-35
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• 2010

Asphalt Plug Joint(APJ) is an buried expansion joint that enabling the smooth connection of expansion gap and road pavement by filling the gap with bituminous mixture of 20% bitumen and 80% aggregate by weight, so it secures evenness and expansion or contraction using the material's properties. Although APJ is designed to have a 6-7 year lifecycle, there are some cases where it is damaged within the first six months. This early damage cause traffic congestion due to frequent repair works, and social cost exceeding the installation cost of the joint. So, in this research, we have developed a new system of Buried Folding Lattice Joint(BFLJ) which can overcome the disadvantages of APJ, and have analyzed and compared it's performance with the conventional APJ through experiment with specimens. As a result of the experiment, APJ had crack formation on both ends of the gap plate, spreading to the surface of the expansion joint. With this result, we can conclude that the reason for early damage is the tension failure due to the concentration of strain in the asphalt mixture along the end of gap plate and the debonding along the joint section. In contrast, the newly developed BFLJ induced even transformation in the joint by applying moving stud and high performance material, and resolved APJ's disadvantage of strain concentration. Therefore, it could be seen that the newly developed BFLJ could overcome the disadvantages of APJ and prevent early damage.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.836-839
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• 1997

In recent years, much progress has been made in the automation of welding coped with a variety of highly flexible sensors. Among these sensors, only the eddy current sensor can detect the center location of the butt joint whose gap distance is zero. Thus, in this study the eddy current sensor is used to develop a robust and useful joint tracking system. The developed system is tested to qualify the performance of the system and seam tracking algorithm is proposed and two simulation are executed to show the performance of the proposed tracking algorithm.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.68-74
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• 2016

Adoption of narrow gap welding shall be increased for the butt joint of thick plate, because the deformation and welding cost is reduced by decrease of cross-sectional area. However, sometimes narrow gap causes defects such as lack of fusion since it has small groove angle and narrow groove width. Therefore, GMAW, GTAW and SAW process shall be adopted to narrow gap welding with small bead hight and low deposition rate. In this study, Super-TIG welding using C-type strip was applied to semi-narrow gap butt joint in order to increase the welding productivity. High deposition rate 10kg/hr was obtained by high current 600A without undercut, humping bead and other welding defects. Measuring the mean and standard deviation of the melting depth to evaluate the developed processes, the fusion line type was determined by measuring the difference between maximum and minium melting depth. Furthermore, a model on arch fusion line and linear fusion line was suggested in order to prevent LF on groove wall in narrow gap butt welding.

• Laser Solutions
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• v.5 no.1
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• pp.33-42
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• 2002

In order to investigate the characteristics of the plasma induced by lap-joint CO$_2$ laser welding of automotive steel sheets, the effects of welding speed, shield gas flow rate, gap size, and laser beam defocus to plasma intensity emitted from keyhole have been investigated. The plasma light is measured by fiber and photodiode. Also, the plasma images were captured by the high speed digital camera in 1000frames/sec in order to correlate the plasma light signal with plasma pattern. From the results, it is observed that the difference of the plasma intensity for between the deep penetration and partial penetration exists from 1.2 to 2 times. The plasma light intensity decreased in case of the deep penetration Is observed due to the exhausting of the plasma gas under the sheet. On the other hand, under the conditions of the deep penetration, the plasma intensity is significantly increased by controling the conditions decreasing the penetration depth. It was specially founded that the effect of 0.3mm gap size at partial penetration condition is approximately similar to deep penetration in 0mm gap. It is concluded that the plasma intensity is able to evaluate the penetration depth in lap-joint welding and appears to offer the most straightforward correlation to the welding process.