• Proceedings of the KWS Conference
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• 2002.10a
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• pp.151-155
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• 2002

In GMA(Gas Metal Arc)Welding, the weld size that is a locally melted area of a workpiece is one of the most important considerations in determining the strength of a welded structure. Variations in the weld power and the welding heat flux may affect the weld pool formation and ultimately the size of the weld. Therefore, an accurate prediction of the weld size requires a precise analysis of the weld thermal cycle. In this study, a model which can estimate the weld bead geometry and a method for thermal analysis, including the model, are suggested. In order to analyze the weld bead geometry, a mathematical model was developed with transformed coordinates to apply to the horizontal fillet joints. A heat flow analysis was performed with a two dimensional finite element model that was adopted for computing the base metal melting zone. The reliability of the proposed model and the thermal analysis was evaluated through experiments, and the results showed that the proposed model was very effective for predicting the weld bead shape and good correspondence in melting zone of the base metal.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.67-71
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• 2005

This paper is concerned with a study on fracture strength of composites in an adhesive single lap joint. The tests were carried out on joint specimens made with hybrid stacked composites consisting of the polyester and bamboo natural fiber layer. The main objective of this work was to evaluate the fracture properties adjacent to adhesive bonded joint of natural fiber reinforced composite specimens. From the results, natural fiber reinforced composites have lower tensile strength than the original polyester. But tensile-shear strength of natural fiber reinforced composites with bamboo layer far from adhesive bond is as high as that of the original polyester adhesive bonded joints. Spew filet at the end of the overlap reduced the stress concentration at the bonded area. Spew fillet and position of bamboo natural fiber layer have a peat effect on the tensile-shear strength of natural fiber reinforced composites including adhesive bonded joints.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.709-720
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• 1998

In order to study the distribution of welding residual stress through the plate thickness. experiment and analysis of fillet welding details were carried out. Especially, a residual stress in the weld root part of T-joint fillet weld whose measurement was difficult up to now was measured. By using the heat input and the number of the weld layers as parameters, the distribution of the 3-dimensional residual stress was investigated. As a result, we can say that with increasing the heat input, the residual stress in the weld toe and weld root barely changes. But, the area of the tensile residual stress became wide. Then, comparing a single pass with multi-pass weld method, it was found that the residual stress decreased more in multi-pass than in single pass. Moreover, it was found the thing that the area of tensile residual stress by multi-pass is lower than that by single-pass in the near weld part.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.55-62
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• 1985

This study modeled in axisymmetric solid elements and analyzed the neighbourhood of the contact surface zone between liner and block in a diesel engine. The results of finite element analysis show that this model is deformed by bolt jointed load and pressure load and that stresses can vary much due to major dimensional changes in the joint area. Guidelines have been developed for selecting fillet radii and for the width of the contact area between liner and block.

• The Korean Journal of Food And Nutrition
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• v.10 no.4
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• pp.553-558
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• 1997

Frozen cod fillet block(7.0$\times$4.6$\times$0.6cm, 18$\pm$0.5g) was purchased from a supermarket in Taegu area. Three experimental groups of fish fillet, frozen-thawed cod fillet refrigerated at 5$^{\circ}C$(R), frozen at -2$0^{\circ}C$(F) and repeated freezing and refrigerating(RFR) every other day, were incubated at each temperature. Changes in the viable counts of mesophiles and psychrotrops, the amount of free drip and pH of cod muscle during cold storage were 6.5$\times$104 and 7.4$\times$103 CFU/g of muscle, respectively. The viable counts of cod muscle R and FRF exceeded 107 CFU/g within 8 days and 16 days, respectively, while the viable counts of cod muscle F were not exceeded 107 cells/g throughout the storage period. The viable counts of psychrotrops exceeded that of mesophiles at the end of cold storage period. The viable counts of cod muscle showed positive correlation with pH(r=0.73-0.96,the highest in RFR) during cold storage. The amount of free drip in cod muscle R, F and RFR was 27.06$\pm$9.75, 27.56$\pm$8.02 and 33.97$\pm$10.70%, respectively. The amount of free drip in RFR increased as the progress of storage.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.3
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• pp.85-94
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• 1984

The WILDHABER-NOVIKOV gear, one of the circular arc gears, has the large contact area between the convex and concave profiled mating teeth, moves from one end of the tooth to the other axially making a face contact. Hence it provides a large load capacity than the Involute gear and still satisfying the law of gearing. In order to analyze the gear stress, a photoelastic investigation was carried out. Photo elastic model of the WILDHABER-NOVIKOV gears were made of Araldite CT200 in this investigation. For both the many teeth gear and the few teeth gear segments, External gears of all addendum type WILDHABER-NOVIKOV gear and the involute gear were tested. Included were the models with various profile raddi at the same pressure angle 20 .deg. and module 13.5. The flank stresses and fillet stresses of these gears were observed in each case and compared with those of gears. From this investigation, the following results were obtained. A. In the case of having many teeth gear: As the profile radius is increased, the fillet stresses of the WILDHABER-NOVIKOV gear become the same or less than that of the INVOLUTE gea, and the flank stress becomes smaller than that of the INVOLUTE gear. Therefore the better design condition is satisfied with a large profile radius. B. IN the case of having a few teeth gear: As the profile radius is increased the flank stress of WILDHABER-NOVIKOV gear becomes smaller than that of the INVOLUTE gear, but the fillet stresses become larger than that of the INVOLUTE gear. Therefore the larger design condition is satisfied with small profile radius.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.79-83
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• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• Plant Journal
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• v.7 no.1
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• pp.49-55
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• 2011

This study analyzed causes and status of cracks to suggest preventives for welding cracks generated on fillet welding zone of atmosphere corrosion resisting steel box girder. Penetrant testing, a sort of non-destructive testing, was conducted for inspection of crack status on welding zone. As a result of test, welding cracks were found on the point of start, center and end to fillet welding zone of 32 mm-thickness. The result of carbon equivalent composition of materials was 0.452%. According to welding specification, to preheat prevent welding crack, preheat temperature of $100{\sim}200^{\circ}C$ should be kept before welding execution. It was failed to keep preheat temperature because it had been executed on winter season and the structure of box girder had wide heat transfer area. As a result of examination of time varying preheating temperature of 32mm-thickness material, it was understood that preheat temperature of above $230^{\circ}C$ on both 130mm-long sides of welded joint can prevent welding crack.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.93-98
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• 2022

Adiabatic blanking is a method to improve productivity through an autocatalytic cycle that occurs repeatedly through plastic deformation and thermal softening caused by impact energy. In this study, an axisymmetric analysis model comprising a punch, die, holder, and specimen was developed to confirm the temperature and deformation characteristics caused by an impact load. Through this, the impact energy, diameter of the punch, gap between the punch and die, and the effect of the fillet were analyzed. Because this process occurs in a very short time, adiabatic analysis can be performed using the explicit time-integration method. The analysis, confirmed that it is necessary to design a structure capable of increasing the local temperature and plastic deformation by controlling the impact energy, working area, gap, and the fillet.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.131-139
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• 1996

The response of the arc sensor using the welding current and/or welding voltage as its outputs has been obtained by the analysis and/or experiments of the static characteristics of arc sensor. But in order to improve the reliability of arc sensor, it is necessary to know its dynamic characteristics. So in this paper, it is presented the dynamic model of arc sensor including the power source, arc voltage, electrode burnoff rate, and wire feed rate. A numerical simulation of the dynamic model of arc sensor was implemented, computing the welding current with input of CTWD. The results of computer simulations and experiments of $CO_2$arc welding showed that a linear relationship between weaving center - weld line distance and current area difference was established. Additionally, a real-time weld seam tracking system interfaced with industrial welding robot was constructed, the result of the weld seam tracking experiment for weld line with an initial offset error of 5$^{\circ}$was good.