• Journal of Welding and Joining
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• v.32 no.2
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• pp.43-47
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• 2014

Famous artificial neural network (ANN) is applied to predict proper process window of arc welding. Target weldment is variously combined lap joint fillet welding of automotive steel plates. ANN's system variable such as number of hidden layers, perceptrons and transfer function are carefully selected through case by case test. Input variables are welding condition and steel plate combination, for example, welding machine type, shield gas composition, current, speed and strength, thickness of base material. The number of each input variable referred in welding experiment is counted and provided to make it possible to presume the qualitative precision and limit of prediction. One of experimental process windows is excluded for predictability estimation and the rest are applied for neural network training. As expected from basic ANN theory, experimental condition composed of frequently referred input variables showed relatively more precise prediction while rarely referred set showed poorer result. As conclusion, application of ANN to arc welding process window derivation showed comparatively practical feasibility while it still needs more training for higher precision.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.7-13
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• 2000

Forming characteristics of tailored blank are mostly effected by the welding method. Recently, laser welding is widely used for the tailored blank. However, tensile and forming characteristics vary due to welding conditions such as welding speed, heat flux etc. The objective of this paper is to evaluate the effect of welding speed on the tensile and forming characteristics of laser welded tailored blank. For this purpose, tailored blank specimens with different welding speed were prepared and tensile tests were performed. Also forming tests such as LDH and OSU test, were performed to evaluate the effect of welding speed on the forming characteristics. Finally, forming limit diagrams were obtained for different welding speed.

• Journal of Welding and Joining
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• v.24 no.3
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• pp.22-26
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• 2006

It is necessary to investigate the welding performance and fracture resistance of welding part in structure. This study presented a most suitable condition of welding process for butt and lap joints by $CO_2$ arc welding which is widely used in the vehicle structure. Also it was conducted to tensile and fatigue test under various welding conditions. For butt and lap joints, the best conditions of welding voltage and current were 30V and 320A, respectively, in 3.2 and 4.5 mm thick steel plate. Under this condition it could be taken the highest tensile strength and fatigue strength, and a good bead appearance.

• Laser Solutions
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• v.2 no.1
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• pp.61-67
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• 1999

This study introduces the new concept in the evaluation criteria of the $CO_2$ laser Tailored Blank weldability, The materials used are 0.7mm, 1.5mm thick low carbon automotive galvanized steels. Welding tests were conducted for both similar thickness(0.7mm-0.7mm, 1.5mm-1.5mm) and dissimilar thickness(0.7mm-1.5mm) cases. The criteria developed for optimum welding conditions were based on relationship between results of die press forming test, weld transverse tensile test Erichsen test and weld penetration measurements. Application of the developed criteria(fracture ratio, strength ratio and D/To) in obtaining optimum welding condition revealed that a weld which satisfied any of the criteria did not fracture during actual die press test.

• Journal of Welding and Joining
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• v.27 no.5
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• pp.34-41
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• 2009

Thermal and mechanical characteristics in dissimilar SS400-STS304 steel weldment have been investigated by 3D thermal elastic-plastic analysis. Moreover, the influence of welding residual stresses on the mechanical behaviour of this welded joint, by applying superimposed external load (tension load) was determined. The residual stresses obtained by numerical simulation were compared with the experimentally measured results. The FE results were in good agreement with the measured values. The mechanical test (hardness, tensile test) and metallurgical analysis was carried out to ensure the weld integrity. Hence, possibility of applying SS400-STS304 dissimilar steels in industries has been established.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.50-57
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• 2013

The high temperature thermal attacks in welding can affect the residual stress of a frame for automotive assembly accompanying frame deformation. Also the residual stress can induce the negative effect on durability performance of the automobile. In order to analyze the frame deformation, the simplified test frame which had the similar shape (form) of the real automotive frame was fabricated. The contactless optical 3D scanner was used for the shape difference measurement of the frame between before and after the welding. The FE-model of the test frame was composed and the deformation and residual stress simulation were performed. The simulated results were compared with the measured results for the reference of the frame design following as the variation of welding sequency. The deformation shape of the frame by simulation was in good agreement with that by the experimental measurement. In addition, the optimized welding sequency with reduced deformation after welding could be achieved through these analyses.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.54-60
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• 2016

In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of three types of austenitic stainless steels (type 310: A mode, type 316-A: AF mode, type 316-B: FA mode solidifications), the laser beam welding (LBW) transverse-Varestraint tests consisted of multi-mode fiber laser, welding robot and hydraulic pressure system were performed. As the welding speed increased from 1.67 to 40.0 mm/s, the solidification brittle temperature range (BTR) of laser welds for type 316 stainless steels enlarged (316-A: from 37 to 46 K, 316-B: from 14 to 40 K), while the BTR for type 310 stainless steel reduced from 146 to 120 K. In other words, it founds that solidification cracking susceptibility could not be simply mitigated through application of LBW process, and the BTR variation behavior is quite different upon solidification mode of austenitic stainless steels.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.55-60
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• 2001

The automobile is made up of thousands of parts. Some parts are formed by pressing and combined by spot welding. To find weldability conditions of spot welding, clearance between two welding plates was made and after spot welding, weldability is evaluated by means of tensile shear load, nugget size and shape. Specimen used in this study was a steel plate of 1.2mm thickness and electrode was Cu-Cr alloy of 6mm diameter. When spot welding started, the clearance of two specimens was changed 0mm, 3mm and 5mm and distance from vise to measure influence of bending moment 25mm, 45mm, 65mm step by step. The fractured surface of specimen after this test was observed by Optical Microscope to measure microstructure and nugget shape. When clearance of two specimen was 3mm and 5mm, strength and nugget size was decreased and nugget shape was not clear. The much bending moment and crosshead speed are the much tensile shear load is.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.381-389
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• 2001

The objective of this paper is to evaluate the fracture resistance characteristics of SA508 Cl.1a to SA508 Cl.3 welds manufactured for the reactor coolant loop piping system of nuclear power plants. The effect of the crack plane orientation to the welding process orientation and the preheat temperature on the fracture resistance characteristics were discussed. Results of the fracture resistance test showed that the effect of the crack plane orientation to the welding process orientation of the fracture toughness is significant, while that of preheat temperature on the fracture toughness is negligible. The micro Vickers hardness test, the metallographic observation and the fractography analysis were conducted to analyse the crack jump phenomenon on the L-R crack plane orientation in the multi-pass welding zone. As these results, it is shown that the crack jump phenomenon was produced because of the inhomogeneity between welding beads and the crack plane orientation must be considered for the safety of the welding zone in the piping system.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.11a
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• pp.257-262
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• 2002

The object of this study is to investigate the effect of compounded welding through the AE (Acoustic Emission) characteristics for weld HAZ (Heat Affected Zone) on static tensile test. This study was carried out a SM 490A, high tension steel using the low hydrogen type E4316 of electronic shield metal arc welding, compound wire of $CO_2$ gas arc welding and tungsten electrode of TIG welding.