• Journal of Welding and Joining
• /
• v.29 no.5
• /
• pp.24-30
• /
• 2011

• Journal of Welding and Joining
• /
• v.30 no.3
• /
• pp.4-14
• /
• 2012

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.10
• /
• pp.141-151
• /
• 1999

The resistance Spot Welding is widely used in the field of assembling the plates. However we don't still have any satisfactory solution, which is non-destructive quality evaluation in real-time or on-line, against it. Moreover, even though the rate of welding under the condition of expulsion has been high until now, quality control of welding against expulsion hasn't still been established. In this paper, it was proposed on the quality assurance technique of resistance spot welding pieces using Neuro-Fuzzy algorithm. Four parameters from electrode separation signal in the case of non-expulsion, and dynamic resistance patterns in the case of expulsion are selected as fuzzy input parameters. The parameters consist of Fuzzy Inference System are determined through Neuro-Learning algorithm. And then, fuzzy Inference System is constructed. It was confirmed that the fuzzy inference values of strength have within ${\pm}$4% error specimen in comparison with real strength for the total strength range, and the specimen percent having within ${\pm}$1% error was 88.8%. According to KS(Korean Industrial Standard), tensile-shear strength limit for electric coated of zinc is 400kgf/mm2. Judging to the quality of welding is good or bad, according to this criterion and the results of inference, the probability of misjudgement that good quality is valuated into poor one was 0.43%, on contrary it was 2.59%. Finally, the proposed Neuro-Fuzzy Inference System can infer the tensile-shear strength of resistance spot welding pieces with high performance for all cases-non-expulsion and expulsion. And On-Line Welding Quality Inspection System will be realized sooner or later.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.35-36
• /
• 2006

In Nd:YAG laser welding, evaluation methods of welding flaw are various. But, the method due to fume shape is difficult to classification of welding flaw. The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. At the present time, some methods are studied for measurement of fume shape by using high-speed camera and photo diode. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. In this study, fume shape was measured by infrared thermal camera that is non-contact/non-destructive thermal measurement equipment through change of laser generating power, speed, focus. Weld was performed on bead-on method. Measurement results are compared as two equipments. Here, two results are composed of measurement results of fume quantities due to fume shape by infrared thermal camera and inspection results of weld bead include weld flaws by ultrasonic inspector.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.12 no.6
• /
• pp.45-51
• /
• 2013

Friction stir welding using aluminum alloys has been widely applied for transportation vehicles because of the light specific weight, which can be used to obtain sound joint and high mechanical properties. This study shows the effects of rotation speed, welding speed, welding load, and tool shape on defect formation with extruded AA6005, which is used for railway vehicle structures of non-uniform thickness welded by friction stir welding using load control systems. Optical microscopy observations and liquid penetrant testing of each FSW joint were carried out in order to observe defect formation. Two kinds of defects, that of probe wear and that of lack of penetration in the bottom of the welded zone, were observed. In the case of using a taper shaped tool, the defect free zone is very narrow, within 100 kgf; however, in case of using a cylindrical shape tool, the defect free zone is wider.

• Journal of Welding and Joining
• /
• v.3 no.1
• /
• pp.3-10
• /
• 1985

Lamellar tearing susceptibility and through-thickness tensile ductility have been investigated in $40kg/mm^2 and 50kg/mm^2$ class tensile strength steel plates in terms of cleanliness of non-metallic inclusion and welding condition. The plate which had 0.01% cleanliness of A-type inclusion (MnS) had 61% of the reduction of area in the through-thickness direction and did not show lamellar tearing. Lamellar tearing susceptibility decreased with increasing the preheat and interpass temperature. The plate which had 0.04% cleanliness of A-type inclusion did not show lamellar tearing under the condition of 75.deg. C of preheat and interpass temperature.

• Journal of Ocean Engineering and Technology
• /
• v.16 no.1
• /
• pp.64-70
• /
• 2002

This paper shows the results of the development of a small size of digital type continuous and intermittent welding auto-carriage based on microprocessor (Intel 80196KC) for welding process with long welding line. The developed welding auto-carriage loads welding torch and tracks welding line. It is an automaton largely used for welding process with a lot of long welding lines such as shipbuilding and structure. Most traditional auto-carriages have been developed based on analog circuit for open loop control. So this analog circuit welding auto-carriage cannon control welding speed. Specially welding auto-carriage for intermittent welding condition is so complicated and has the low precision of control performance in welding distance and non-welding distance. The auto-carriage developed in this paper has the following characteristics: It has not only functions of traditional carriage but also functions such as pseudo-welding process of big iron structures, intermittent welding in order to limit heat for welding thin plates, crater treatment of the final step of welding, acceleration at the initial step of welding and deceleration in the final step of welding. The main control board of auto-carriage, power supply system and DC motor drive wee developed and manufactured. The welding speed and the welding distance of the developed auto-carriage are controlled accurately by feedback control using photo-sensor. Hardware and software robust against the heat and noise produced on the welding process are developed.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.378-383
• /
• 2002

In previous study, the decrease and recovery of total stiffness in welded structure was discussed on the basis of experimental examination through tensile loading and unloading test of welded specimen. The recovery of structure stiffness was caused by the release of welding residual stress through mechanical loading. In this study, analysis model that is indispensable for the effective application of MSR method was established on the basis of test and measurement result. Thermal elasto-plastic analysis for welding process was performed by non-coupled analysis. Analysis results of welding process were transfer to elasto-plastic model for tensile loading & unloading by restart technique. In elasto-plastic analysis model for mechanical loading & unloading, hardening appearance of weld metal was considered by rezoning technique and tying technique was used for JIG condition of test machine.

• Journal of Welding and Joining
• /
• v.29 no.1
• /
• pp.9-13
• /
• 2011

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2005.05a
• /
• pp.71-76
• /
• 2005

The defects evaluation of the interior and the surface would be considered as vital characteristics in predicting the total life span of the steel structure. More importantly, the understandings in the interior composite of welding zone and the notifications in the presence, the formation, and the positioning of the non-metallic inclusion are necessary as well, since there were signs of relatively high defect frequency presented in the welding zone. The ultrasonic testing is a highly recommended technique chosen from among other techniques because of variety of advantages in conducting the non-destructive testing for the welding zone. However, the ultrasonic testing had technical disadvantages referred as followings; the problems due to the couplant between the PZT and the specimen, the formations that were miniature and complex, the moving subject, and the high temperature surrounding the specimen. This research was conducted to resolve the technical disadvantages of the contact ultrasonic testing by studying the non-contact ultrasonic testing where the ultrasonic waves were transferred by the laser, and revealing the specimen defects at its interior part and its surface part. The ultimate goal of this research was to develop a non-destructive evaluation applying the laser manipulated ultrasonic method for the steel structure.