• Journal of the Korea Furniture Society
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• v.10 no.2
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• pp.73-78
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• 1999

This paper describes the relationship between the bending strength properties of sloped finger-jointed woods and the acoustic emissions(AEs) generated during the test. Rhus verniciflua pieces were cut in sloped-finger types and glued with three kinds of adhesives(polyvinyl acetate, polyvinyl-acryl acetate and oilic urethane resin). The slope ratios of finger joints were 0, 1.0, 1.5, and 2.0. The AE cumulative event count and cumulative count were measured during the bending test. The results were as follows: The lower the bending strength(load) was, the generation time of AE event count got and the higher the increasing rate of AE event count became in the sloped finger-jointed specimens bonded with polyvinyl acetate, polyvinyl-acryl acetate oilic urethane resin adhesives. Therefore, the slope from load-AE cumulative event count was very steep. The patterns of AE event count and count were very similar. The relationship between the MOR and the AE parameter from load and AE cumulatve event count in the early stage of the sloped finger-jointed specimens bonded with polyvinyl acetate, polyvinyl-acryl and oilic urethane resin adhesives was much greater than that between the MOE and the MOR. Therefore, the AE signals obtained during bending test are useful for estimating the strength of sloped finger-jointed Rhus verniciflua specimens.

• Journal of Welding and Joining
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• v.5 no.4
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• pp.22-27
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• 1987

The debonding of clad steel was often occurred at interface between stainless steel and carbon steel during the fabrication of pressure vessel. In order to clarify the causes of debonding phenomena, the fabrication sequences were fully analyzed. As a result, possible factors were noticed for causing the debonding of clad steel, that is, thermal treatment on weldment and welding. Moreover the existence of hydrogen diffused from surroundings also expedites the debonding of clad steel. In this stud, the effect of welding thermal cycle, hydrogen and mixed condition under thermal treatment on the interfacial strength of clad steel were investigated to understand the debonding mechanism of clad steel. From this study, it has been confirmed that the interfacial strength of clad steel was remarkablely deteriorated due to welding and/or existence of hydrogen under thermal treatment. In the case of welding thermal cycle effect, the higher temperature at interface experienced by welding, the more reduction in interfacial strength of clad steel resulted in. And the existence of diffusible hydrogen also reduced the interfacial strength. It is also found that the interfacial strength of clad steel became much lower value than that of the as-received plate under coexistence of above mentioned factors.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.68-77
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• 2003

It is important to understand the characteristics of material strength and fracture under the dynamic loading like as earthquakes to assure the integrity of welded structures. The characteristics of dynamic strength and fracture in structural steels and their welded joints should be evaluated based on the effects of the strain rate and the service temperature. It is difficult to predict or measure temperature rise history with the corresponding stress-strain behavior. In particular, material behaviors beyond the uniform elongation can not be precisely evaluated, though the behavior at large strain region after the maximum loading point is much important for the evaluation of fracture. In this paper, the coupling phenomena of temperature and stress-strain fields under the dynamic loading was simulated by using the finite element method. The modified rate-temperature parameter was defined by accounting for the effect of temperature rise under the dynamic deformation, and it was applied to the fully-coupled analysis between heat conduction and thermal elastic-plastic behavior. Temperature rise and stress-strain behavior including complicated phenomena were studies after the maximum loading point in structural steels and their undermatched joints and compared with the measured values.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.80-86
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• 2014

We have successfully fabricated high strengthening Cu/STS/Cu 3 layered clad metal of $70kgf/mm^2$ grade for electric device lead frame, and investigated thermal effect of the mechanical and physical properties on the Cu/STS/Cu 3 layered clad metal lead frame material at different temperatures ranging from RT to $200^{\circ}C$. The fabricated clad metal shows a good thermal stability under 6% degrading of mechanical tensile strength and hardness change at $200^{\circ}C$ and also physical properties show stable thermal and electrical conductance of over $220W/m{\cdot}K$ and 58.44% IACS upto the $200^{\circ}$. The results confirm that fabricated high strengthening Cu/STS/Cu 3 layered clad metal can be applied for the high performed electrical lead frame devices.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1146-1152
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• 2005

Recently, multi cell tube which is used for a cooling system of automobiles is mainly manufactured by the conform extrusion but this method is inferior as compared with direct extrusion in productivity per the unit time and in the equipment investment. Therefore, it is essential for the conversion of direct extrusion with porthole die. The direct extrusion with porthole die can produce multi cell tube which has the competitive power in costs and qualities compared with the existing conform extrusion. This study is designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection that is affected by variation of porthole shape in porthole die. Estimation is carried out using finite element method under the non-steady state. Also this study was examined into the cause of mandrel fracture through investigating elastic deformation of mandrel during the extrusion.

• Composites Research
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• v.12 no.1
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• pp.19-27
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• 1999

A design development test for carbon/epoxy composite laminates for an aircraft flight control system is performed. The design development test includes moisture absorbing test, tensile, compressive, bearing and lap shear tests. The moisture absorbing behavior for different fiber orientation angles is investigated and the changes in mechanical characteristics are compared. In the in-plane tensile test, the effect of damages such as scratches and impacts is studied. The bearing test is performed for different fastening types. The resulting design allowable stress and environmental load enhancement factor are used for the structural analysis and certification tests for the flight control system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.739-746
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• 2014

The objective of this test series was to determine shear load per unit length which causes a unit slip in the fastener joint. The shear load is one of major factors which reflect partial composite action for cold-formed steel wall stud panels. Test method used were based on the methods presented in the 1962 AISI Specification. According to the comparison with experimental strength, it is seen that the shear loads used in nominal axial strength predictions made acceptable results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.829-836
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• 2009

3-Dimensional flow which is represented by horseshoe vortex is generated as a type of secondary flow about the main flow. As well, it causes the flow loss. The present study deals with the leading edge fence shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge fence was optimized with the design variables of the installed height, length, width, and thickness of the fence as the design variables. Approximate optimization design method is used as the optimization. The study was investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. Total pressure coefficient of the optimized design case was decreased about 7.5 % compare to the baseline case.

• Journal of Welding and Joining
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• v.6 no.2
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• pp.56-63
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• 1988

The effects of PWHT (poste weld heat treatment) and stress simulating the residual stress during PWHT in weld HAZ of low and high strength steels on corrosion fatigue crack growth were evaluated. The obtained results are summarized as follows. 1. Fatigue crack growth rate of HAZ in air and 3.5% NaCl solution was slower than that of parent due to the signgularity in weld HAZ. 2. In the case of HT-80, 3.5% NaCl solutio nacts to accelerate the crack growth for all specimens, and the sensitivity of as-weld to corrosion environment was the greatest among other PWHT specimens. 3. Corrosion fatigue crack growth of parent, as-weld and PWHT speciments ofr SS41 as well as SM53B was retarded in comparison with the fatigue crack growth in air. 4. There was a tendency that crack growth of PWHT specimens subjected $10kg/mm^2$ was faster than that of PWHT specimens without stress during PWHT. 5. The retardation phenomenon of crack growth in corrosion environment is attributed to the crack branching decreased .DELTA.K due to the corrosion products and multi-cracks.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.29-32
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• 2002

The mechanical joining process of a sheet metal pair has been developed in order to replace the resistance spot welding process in case that joining of mechanically unweldable materials and coated sheet metals with different thickness are needed. Form-joining or clinching, a kind of mechanical joining process, is defined as joining process of a sheet metal pair by geometric constraint imposed by plastic deformation of workpieces without any additive part. It has been reported that the joining strength by commercial form-joining apparatus is 50∼70 percent of that by resistance spot welding. Therefore, a two-step form-joining process with a secondary punch is proposed. The device is designed to improve the joining strength by increasing the geometric constraint of the deformed shape by combining a primary punch, a secondary punch and a female die. In order to verify the improved joining strength by the designed process, the tensile-shear strength, the peel-tension strength and the asymmetric peel-tension strength are compared with those by the TOX process and resistance spot welding.