• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.148-159
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• 1998

Spot welding palys a key role in increasing productivity and weight reduction of the final products. This paper proposes a systematic approach on the design of spot weld configuration, dealing with the requried number and location of spot weld joints under the given design parameters, such as the applied loads, lap area, and individual spot weld strength. The optimal design of a spot-welded joint is postulated as a state when the safety factors of all spot weld points (i) are evenly distributed and (ii) reach maximum value. A CAD program is developed to arrange the optimal location of each spot weld based on the derived objective function and constraints. The CAD tool integrates the optimization procedure with Finite Element Analysis (FEA) code through an interface. The interface automatically provides geometrical data and mesh configuration for different spot weld locations to FEA model. It also extracts the transmitted load of each spot weld from the FEA code, and allows the optimization code predict an improved arrangement of spot weld locations. The feasibility of the developed approach is demonstrated by the selected examples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.471-478
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• 2002

In real structures, multi-spot welded joints are more frequently used than a single-spot welded joint. Most researches, however, have been focused to a single-spot welded joint until now. In this paper, the fatigue behavior of multi-spot welded joints are investigated using the finite element solutions of the multi-spot welded specimens. The local strain approach is used rather than the stress intensity factor approach to estimate the fatigue life since the former is quite simple and straightforward. It is found that the fatigue behavior of multi-spot welded joints is different from that of single-spot welded joints. The local strain approach is still applicable to multi-spot welded joints.

• Journal of the Korea society of information convergence
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• v.7 no.2
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• pp.59-65
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• 2014

Grassfire spot matching method is based on similarity comparison of topological patterns for neighbor spots. This is a method where spot matching is performed as if fire spreads all around on grass. Spot matching starts from a seed spot pair confirmed as a matched pair of spots and spot matching spreads to the direction where the best matching result is produced. In this paper, it is a bit complicated way of grassfire method where multi-seed matched spot pair are manually selected and spot matching is performed from each multi-seed matched spot pair. The proposed method shows better performance in detection rate and accuracy than that of the previous method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.38-51
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• 2000

The study on the mechanical behavior of a spot-welded specimen is largely divided into the quasi-static overload failure analysis and the fatigue failure prediction. The main issue in an overload analysis is to examine the critical loads, thereby providing a generalized overload failure criterion. As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. In this study, we first present the limit loads of 4 representative types of single spot-welded specimens in terms of the base metal yield strength and specimen geometries. Recasting the load vs. fatigue life relationships experimentally, obtained here, we then predict the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key, role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot.

• Applied Biological Chemistry
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• v.17 no.2
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• pp.125-137
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• 1974

The chemical structure of glycolipid of Selenomonas ruminantium cell wall was to be elucidated. The bacterial cells were treated in hot TCA and the glycolipid fractions were extracted by the solvent $CHCl_3\;:\;CH_3OH$ (1 : 3). The extracted glycolipids fraction was further separated by acetone extraction. The acetone soluble fraction was named as the spot A-compound. The acetone insoluble but ether soluble fraction was named as the spot B-compound. These two compounds were examined for elucidation of their chemical structure. The results were as follows: 1. The IR spectral analysis showed that O-acyl and N-acyl fatty acids were linked to glucosamine moiety in the spot A-compound. However in the spot B-compound in addition to O and N-acyl acids phosphorus was shown to be attached to glucosamine. 2. It was recognized by gas liquid chromatography that spot A compound contained beta-OH $C_{13:0}$ fatty acid in predominance in addition to the fatty acid with beta-OH $C_{9:0}$, whereas the spot B compound was composed of the predominant fatty acid of beta-OH $C_{13:0}$ with small amount of beta-OH $C_{9:0}$. 3. According to the paper chromatographic analysis of hydrazinolysis products of the spot A compound, a compound of a similar Rf value as the chitobiose was recognized, which indicated a structure of two molecules glucosamine condensed. The low Rf value of the hydrazinolysis product of the spot B-compound confirmed the presence of phosphorus attached to glucosamine. 4. The appearance of arabinose resulting from. ninhydrin decomposition of the acid hydrolyzate of the spot A compound indicated that the amino group is attached to $C_2$ of glucosamine. 5. The amount of glucosamine in the N-acetylated spot A compound decreased in half of the original content by the treatment. with $NaBH_4$, indicating that there are two molecules of glucosamines in the spot A compound. The presence of 1, 6-linkage between two molecules of glucosamine was suggested by the Morgan-Elson reaction and confirmed by the periodate decomposition test. 6. By the action of ${\beta}-N-acetyl$ glucosaminidase the N-acetylated spot A compound was completely decomposed into N-acetyl glucosamine, whereas the spot B compound was not. This indicated the spot A compound has a beta-linkage. 7. When phosphodiesterase or phosphomonoesterase acted on $^{32}P-labeled$ spot B compound, $^{32}P$ was not released by phosphodiesterase, but completely released by phosphomonoesterase. This indicated that one phosphorus is linked to glucosamine moiety. 8. The spot A compound is assumed to have the following chemical structure: That is glucosaminyl, ${\beta}-1$, 6-glucosamine to which O-acyl and N-acyl fatty acids are linked, of which the predominant fatty acid is beta-OH $C_{13:0}$ fatty acid in addition to beta-OH $C_{9:0}$ fatty acid 9. The spot B compound is likely to have the linkage of $glucosaminyl-{\beta}-1$, 6-glucosamine to which phosphorus is linked in monoester linkage. Furthermore both O-acyl and N-acyl fatty acids contained beta-OH $C_{13:0}$ fatty acid predominantly in addition to beta-OH $C_{9:0}$ fatty acid.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.197-209
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• 1995

This paper is a third report about the new fungal diseases of economic resource plants in Korea. It contains short descriptions on symptoms, occurrence conditions, pathogen, and some phytopathological notes for each of 10 fungal plant diseases. They are angular leaf spot of Achyranthes japonica by Cercospora achyranthis causing leaf spot and defoliation in the shade of plants, leaf spot of Armoracia lapathifolia by Cercospora armoraciae causing leaf spot to blight from the rainy season to autumn, hypophyllous mold of Dioscorea tokoro by Distocercospora pachyderma causing leaf spot and yellowing, hypophyllous mold of Artemisia spp.by Mycovellosiella ferruginea causing leaf spot and yellowing, angular leaf spot of Aralia elata by Pseudocercospora araliae causing velvety leaf spot and defoliation, hypophyllous mold of Lycium chinense by Pseudocercospora chengtuensis causing velvety leaf spot and defoliation from the rainy season to autumn, angular leaf spot of Diospyros lotus by Pseudocercospora disospyri-morrisianae causing leaf spot and defoliation from summer to autumn, brown leaf spot of Impatiens textori by Pseudocercospora nojimae causing leaf spot to blight from the rainy season, leaf spot of Cephalonoplos segetum by Ramularia cirsii causing leaf spot to blight throughout the growing season, and white mold of Leonurus sibiricus by Ramularia leonuri causing leaf spot to blight mostly in autumn.

• Transactions of Materials Processing
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• v.23 no.5
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• pp.282-288
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• 2014

It is difficult to control welding variables during spot welding of non-ferrous metals like aluminum because of the low electrical resistance of the material. It has been suggested that a solid state welding process such as friction stir spot welding or extru-spot welding can be used to spot weld aluminum plates. In the extru-spot welding, there is a need to increase the weld strength by improving the shape of the welding die. The current study shows that the weld strength for an extru-spot welding can be increased by using a pin placed on the inside of the upper electrode in the welding die. In the current study, the deformed shape of the insert rivet and the stress distribution in the welding zone were analyzed by simulation. Extru-rivet spot welding experiments were performed by changing the height of pin on the inside of the upper electrode. From the experimental result, it is shown that the weld strength for an extru-rivet spot welding can be increased by adjusting the height of the pin. The optimal shape of the deformed rivet after the extru-rivet spot welding can be observed from the simulation results. The deformed shape of the insert rivet can also be controlled by the height of pin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1065-1070
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• 2003

In arc spot welding process, the arc is not moving and heat input is concentrated in one spot so that the heat input efficiency of arc is higher than that of GMAW. In other words, the heat input efficiency of arc change during weld time because arc start is done in spot and weld metal is filled. Therefore, the heat input model of arc spot welding should be different from that of general GMAW. In present study, the calculating model of heat input efficiency in arc spot welding was suggested by temperature monitoring near spot in arc spot welding of copper plate. The result showed that the heat input efficiency of arc was changed three times during weld time. The accuracy of calculating method of heat input efficiency was verified by heat transfer analysis of arc spot welding process using finite element method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.554-561
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• 1998

Vehicle body structures are formed by thousands of spot welds and fatigue failure of vehicle structures occur near the spot welds after driving a long way at a durability test road. It is necessary to know accurately the reason of the fatigue failure of the spot weld in the developing stage in order to reinforce it. Many investigations have been done regarding the strength of spot welded joints, contributing to understand its fatigue strength. In developing process, a fatigue failed spot welded area can be repaired by $CO_2$ welding or another method to continue the test. To know the effect of reinforcing these welds, several methods of welding were analyzed and compared to spot welding. With the results of this test, the appropriate repair method can be used instead of spot welding during the development of new car and best design guide can be given for the strength. In this study, fatigue and static tensile tests are made and microstructure is investigated for the purpose of estimating the strength of welded joints by using spot welded and $CO_2$ plug welded specimens. The tested specimens are of two types : Tensile-shear type(TS) and L-tension type(LT).

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.41-49
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• 1997

Laser spot welding offers a unique combination of high speed. precision and low heat distortion, compared with conventional resistance spot welding. This combinatin of advantages is especially attractive for the automotive industry. Until now automobile fabrication is widely used resistance spot welding, however, because of geometric and structural problem, spot welding is required many welding machine in that reason by substituting spot welding with laser welding, it save the equipment cost. In the present study we measured ultimate strength and observed bead cross section of laser welded specimen and compared with that of the resistance spot welding results in order to adapt laser welding in automobile industry. Also for strength esti- mation we calculated the residual stress of laser welded zone. All calculations are performed with the ABAQUS code on a workstation.