• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.68-76
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• 1997

The welding-induced initial imperfections such as residual stresses and initial strains in plated structures of ships and offshore structures can be effectively evaluated by the thermal elasto-plastic analysis method proposed in this paper. In the analysis of heat conduction of plate structures, both the analytical method and the numerical method are used. For the thermal elasto-plastic analysis of plates, the finite element analysis is performed, based on the initial strain method. In the plastic domain during incremental process, the 2nd order terms of stress increments and yield stress increments were considered, so that time increment could be controlled for more stable solution. To measure temperature distribution and angular distortion of plates during welding, bead-on-plate experiment are perform with various heat input and plate thickness. Measured data show good agreement with the calculated results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.96-101
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• 2020

In this paper, we present the results of our research to perform 3D laser scanning functions by adding a focusing lens to a conventional 2D laser scanner. For the optical design, the ray-tracing technique was used along with a total of four lenses as the variable incident focusing lens, the collimating lens, and the F-Theta lens. As design variables, the curvature of the incident focusing lens (Lens #1) was assumed to be us, l mm and sumed mm, and the incident angles were set at 0cidenus, l. In addition, the distance between the focusing lens and the collimating lens was set to vary from 5 mm to 15 mm. When the incident focal length was varied from 5 mm to 15 mm, the exit focal length was calculated to vary from 67.5 mm to 56.8 mm for the lens with R = 100 mm and from 108.5 mm to 99.0 mm for the lens with R = 150 mm. When the incident angle was 0°, the focal aberration was only slightly observable at 10㎛ in both the x- and y-direction. At 7.5° was the focal aberration of approximately 20~50㎛ was measured at 20㎛. To investigate the chromatic aberration of the designed optical device, the distortion of the focus was observed when the 550 nm beam was simulated on lens designed for a 980 nm wavelength.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.285-288
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• 2003

The bending phenomenon during extruding one product using four billets can be obtain by the difference of hole diameters in the multi-hole container. The difference of hole diameter caused the difference of billet amount inserted in the die cavity. As results, it can bend during extruding products by the different amount of two billets and by the cohesion of billets in the porthole dies cavity. And the bending curvature can be controlled by the size of holes and billets. The experiments using aluminium material had been done for the rectangular and square curved tube product. The results of the experiment show that the curved aluminum tube product can be bended by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. The curvature of product is affected by shape of cross section and the difference of billet diameters. It is known that the welding and extruding and bending can be done simultaneously in the die cavity when a rectangular hollow curved tube would be extruded by porthole dies using four different size billets made of aluminum material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.102-105
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• 2001

The bending process for the curved tube can be developed by the hot metal extrusion machine with the multiple punches moving in the different velocity. The bending phenomenon has been studied to be occurred by the different of velocity at the die extrusion. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the welding of billets inside the porthole die chamber. The multiple billets are moving differently by the multiple extrusion punches controlled by PLC with the servo mechanism units. The results of the experiments show that the curved tube can be bended by the extrusion process and that the defects such as the distortion of section and the thickness change of thick tube, tile folding and wrinkling of thin tube can not be shown after the bending processing by the extrusion bending machine.

• Journal of Computational Design and Engineering
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• v.2 no.4
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• pp.248-252
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• 2015

Currently composite manufacturing process, such as linear friction welding plus NC machining, is the main method for the manufacturing and repairing of complex parts with integrated structure. Due to different datum position and inevitable distortion from different processes, it is important to ensure sufficient machining allowance for complex parts during the NC machining process. In this paper, a workpiece localization approach for machining allowance optimization of complex parts based on CMM inspection is developed. This technique concerns an alignment process to ensure sufficient stock allowance for the single parts as well as the whole integrated parts. The mathematical model of the constrained alignment is firstly established, and then the symmetric block solution strategy is proposed to solve the optimization model. Experiment result shows that the approach is appropriate and feasible to distribute the machining allowance for the single and whole parts for adaptive machining of complex parts.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.5
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• pp.496-503
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• 2007

Although weld-induced deformation is inevitable in shipbuilding, it is important to reduce it as low as possible during fabrication for a more efficient production of ships' blocks. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates, and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the transverse and longitudinal deformation. in order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. Numerical simulation has been also carried out to compare the weld-induced deformation and residual stress. From the present study, it has been found that the tensioning method is very effective on reduction of weld-induced residual stress as well as weld-induced deformation.

• Journal of Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.103-108
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• 2006

It has been well appreciated that reducing weld-induced deformation as law as possible is important during fabrication for a more efficient production of blocks. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the weld-induced deformation. In order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present experimental study, it has been found that the tensioning method is very effective on reduction of weld-induced residual stress as well as weld-induced deformation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.171-179
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• 2020

Recently, studies have shown that convolution neural networks are achieving the best performance in image classification, object detection, and image generation. Vision based defect inspection which is more economical than other defect inspection, is a very important for a factory automation. Although supervised anomaly detection algorithm has far exceeded the performance of traditional machine learning based method, it is inefficient for real industrial field due to its tedious annotation work, In this paper, we propose ADGAN, a unsupervised anomaly detection architecture using the variational autoencoder and the generative adversarial network which give great results in image generation task, and demonstrate whether the proposed network architecture identifies anomalous images well on MNIST benchmark dataset as well as our own welding defect dataset.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.69-77
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• 2003

This paper presents test results on eight reduced beam section(RBS) steel moment connections. The testing program addressed bolted versus welded web connection and panel zone(PZ) strength as key variables, Specimens with medium PZ strength were designed to promote energy dissipation from both PZ and RBS regions such that the requirement for expensive doublet plates could be reduced. Both strong and medium PZ specimens with a welded web connection were able to provide satisfactory connection rotation capacity for special moment-resisting frames. On the other hand, specimens with a bolted web connection performed poorly due to premature brittle fracture of the beam flange of the weld access hole. If fracture within the beam flange groove weld was avoided using quality welding, the fracture tended to move into the beam flange base metal of the weld access hole. Plausible explanation of a higher incidence of base metal fracture in bolted web specimens was presented. The measured strain data confirmed that the classical beam theory dose not provide reliable shear transfer prediction in the connection. The practice of providing web bolts uniformly along the beam depth was brought into question. Criteria for a balanced PZ strength improves the plastic rotation capacity while reduces the amount of beam distortion ore also proposed.