• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.26-33
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• 2014

In this study, Non-load-carrying EH Grade steels in fillet welded joints were evaluated with both the hot spot stress method and the 1mm stress method. The thickness effect criterion for fatigue strength evaluation of welded of welded steel structures recommendations of the IIW was used to evaluate the fatigue strength of EH40 and EH36 and Both EH40 and EH36 have been compared with FAT 125 curve recommended in the IIW. Furthermore, fatigue strength of the welded tow and the ground conditions for Non-load-carrying EH36 based on the 1mm stress method has been discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2845-2852
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• 2000

When welding a car frame with one spot welding there are same limitations because many parts of it cannot be simplified by one spot welding alone. It is presented two spot welding model for the description of the spot welding which is usually used in a car frame structure. This study primarily covers fatigue behavior taking spot welded SPCC(Steel plate carbon C) with different ungget intervals as a tension shear specimen. It was prepared that intervals between two nuggets are varied as 9mm, 14mm, and 20mm respectively. The tensile tests and fatigue tests were executed to know the mechanical properties under static and fatigue load condition. In addition, the relationship between fatigue life and nugget intervals was illustrated by finite element method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.224-231
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• 1984

Having found by means of a tension-shear test an optimal spot welding condition under which the maximum weld strength is to be brought forth, this study made an examination of behavior of fracture concerned with behavior of stress distribution, observed around the nugget periphery of the specimens prepared under the optimal conditions, with one point spot welded mild steel sheets. The resultant findings are as follows: (1)There remarkably exists an optimal spot welding condition to indicate the maximum weld strength, and fracture of the specimens spot welded under that condition occurs outside the nugget boundary. (2)An experiment on the basis of a photoelastic model reveals that the maximum stress is distributed along the center line of the steel plate width but occurs on the region corresponding to heat affected zone of spot welds. (3)Heat affected zone of spot welds consists of coarse grains with considerably low micro Vickers hardness value and of fine grains of high micro Vickers hardness value, and in this unbalanced structure weak region are represented in coarse grain region, where fracture is initiated and continues its propagation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.283-288
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• 2017

A spot welded joint is modeled using 3-D finite elements with embedded strong discontinuities. The spot weld is represented by a special cohesive law on the embedded discontinuity surface, instead of meshing its geometry. This strategy naturally eliminates the need of adaptive FEM meshes fitting the local geometry of the spot weld. Mesh independent solutions are guaranteed by explicitly modeling the detailed shape of the spot weld, which is in contrast with the exiting approach using point constraints for the spot weld.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.80-86
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• 2003

Arc-spot welding is generally used in joining of precise parts such as case and core in electric compressor. It is important to control joining deformation in electric compressor because clearance control of micrometer order is needed for excellent airtightness and anti-nose. The countermeasures for this deformation in field have mainly been dependent on rule of try and error by operator's experience because of productivities. For control this deformation problem without influence on productivities, development of exact simulation model should be needed. In this study, on the basis of previous study, the analysis model io predict deformation of precise order in arc-spot welded structure with non-uniform stiffness is brought up through feedback and tuning between monitoring data and analysis results. For this, deformation monitoring system was built and boundary condition considering mechanical melting temperature was applied.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.579-584
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• 2006

Aluminum Resistance Spot Weld(Al RSW) is an enabling technology for body assembly of low mass fraction vehicles. Due to the unreliable durability of spot-welded joints, applications of Al RSW are limited. This study presents experimental investigation on the use of a post-weld cold working process to improve the fatigue strength of Al RSW. The post-weld cold working process includes special shaped indenters that are pressed or driven into the structure to induce compressive residual stresses. The mechanical properties of the post-weld cold worked Al RSW were investigated, including the experimental results of fatigue and micro-hardness tests. Comparisons of the mechanical properties and qualitative results between the as-welded RSW specimens and the post-weld cold worked RSW specimens are discussed. The post-weld cold worked Al RSW samples had an increase in both microhardness and fatigue life.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1153-1160
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• 2005

Many methods of spot weld modeling have been developed to increase efficiency and guarantee the robustness fer the CAE analysis. In this research they are introduced and the performance is compared in a viewpoint of stiffness and durability. For evaluating the performance a multi-spot welded specimen as well as two single welded specimen is used. The results show that the CWELD element considering 'patch to patch' is stiffer than other modeling methods in stiffness and more conservative in durability. It also offers simple modeling and since it is much easier to maintain the orrhogonality of the BAR element expressing a nugget, we can obtain more exact reaction forces and moments in a nugget. Therefore the CWELD element is the most excellent in the assessment of durability.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.842-847
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• 2001

In order to reinforce the plate in bending spot-welding method is usually used. To analyze the effect of the reinforcement of the plates spot-welded, finite element method was employed to take advantage of the deflection obtained with respect to the change of the aspect ratio and area ratio. The reinforcement effect represented by the equivalent thickness. Was maximum when the aspect ratio was around $1.2{\sim}1.6$ and the area ratio was 0.05.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.69-75
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• 1999

Spot welding has been used in the sheet metal joining processes because of its high productivity and convenience. In this study, predicting methods of fatigue life of spot welded joint have been investigated and fatigue and static tests were conducted with the peel-tension specimens using cold rolled steel plate(SPCC). Fatigue life of peel-tension spot welded joint was influenced by tail effect. Fatigue life evaluation using modified stress index parameter, considering the effective eccentric length, can predict the life more exactly than conventional stress index parameter.

• Journal of Welding and Joining
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• v.24 no.6
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• pp.39-43
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• 2006

A ferritic stainless steel, STS430, and a galvanized steel for case and frame of electronic goods are welded by resistance spot welding and resistance projection welding methods. In this study, resistance spot welding has been performed to investigate the weldability of dissimilar materials such as a ferritic stainless steel and a galvanized steel. Tensile load of the spot weld without heat treatment was 196 kN and brittle fracture occurred at interface between STS430 and nugget due to the high hardness, 380 Hv, in nugget. It was found that the hardness of as-welded nugget increased with higher cooling rate during resistance spot welding by comparing with GTA weld of same materials. Heat treatment by applying second current made nugget softened. Tensile load of heat treated weld increased and reached to 303 kN and fracture occurred at base metal, a galvanized steel.