• Journal of Welding and Joining
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• v.33 no.2
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• pp.23-31
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• 2015

Stainless steel is used in automobile muffler and exhaust systems. However, in comparison with other steels it has a high thermal expansion rate and low thermal conductivity, and undergoes excessive thermal deformation after welding. To address this problem, we evaluated the use of arc brazing in place of welding for the processing of an exhaust system, and investigated the parameters that affect the joint characteristics. Muffler parts STS439 and hot-dipped Al coated steel were used as test specimens, and CuAl brazing wire was used as the filler metal for the cold metal transfer (CMT) welding machine, which is a low heat input arc welder. In addition, a Box-Behnken design of experiment was used, which is a response surface methodology. The main process parameters (current, speed, and torch angle) were used to determine the appropriate welding quality and the mechanical properties of the brazing part was evaluated at the optimal welding condition. The optimal processing condition for arc brazing was 135A current, 51cm/min speed and $74^{\circ}$ torch angle. The process was applied to an actual exhaust system muffler and the prototype was validated by thermal fatigue, thermal shock, and endurance limit tests.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.120-125
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• 2012

Because ships and offshore structures have very large dimensions and complicated shapes, it is difficult to determine the deformation or internal stress in the structure by simple lab tests. Thus, a rigorous analysis by using the computer simulation technology is essential for obtaining their distortions by considering the entire production process characteristics. The rapid development of computer technology made it possible to analyze the heat transfer phenomena, deformation and phase transformation in the welded joint. For large shell structures, shell elements modeling contributed primarily to this development. But if a welding is done by multi-pass, shell elements whose thickness are unchangeable can hard to describe the local situation. Recently, it was researched how to introduce the imaginary temperature for V grooved multi-layer butt welding in strain-boundary method (a kind of shrinkage methodologies). In the present study, we formulated the imaginary temperature for the double bevel and double V groove by considering the thickness change of each pass through the bead and the thickness directions simultaneously and also demonstrated the feasibility of the formula by applying it to the thermal distortion analysis of the erection process of crane pedestal.

• Journal of Welding and Joining
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• v.21 no.6
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• pp.55-63
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• 2003

Welded joint generally has heterogeneity of strength, material, and fracture toughness and it is important to understand the characteristics of material strength and fracture of welded joint considering heterogeneous effect. Characteristics of strength and fracture of an undermatched joint under dynamic loading was studied by round-bar tension tests and thermal elastic-plastic analyses in this paper. The strength and fracture of the undermatched joints should be evaluated based on the effects of the strain rate and the temperature including temperature rise during the dynamic loading. The differences of fracture characteristics like such as ductile-to-brittle transition behavior are well precisely explained from the stress-strain distribution obtained by numerical analysis.

• Nuclear Engineering and Technology
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• v.34 no.6
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• pp.574-585
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• 2002

The microstructural characteristics and its related mechanical properties of RPV cladding have been investigated using small punch (SP) tests. SA508 Cl.3 RPV steel plates were overlay cladded with the type ER309L welding consumables by submerged arc welding process. Although the RPV clad material had a small portion of 5 ferrite phase, it still showed the ductile to brittle transition behavior The transition temperature was determined by the SP test and it depended on the content of $\sigma$ phase, specimen size, and determination methods. The fracture appearance of SP specimen was changed from circumferential to radial cracking as test temperature became low, and below the transition temperature region, ER309L cladding usually fractured along the 6 ferrite by the low temperature failure of ferrite phase.

• Laser Solutions
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• v.4 no.2
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• pp.1-12
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• 2001

This study has been performed to evaluate basic characteristics of CW-CO$_2$ laser welding process of A5083 and A7N01 Al alloy. The effect of welding parameters, such as shielding gas, gas flow rate, laser power and welding speed on the bead shape and porosity from bead on plate welding tests have been investigated. Welds shielded by He gas had deeper penetration and better bead shape than those shielded by Ar. The penetration depth was augmented with the increase of laser Power and the decrease of welding speed. Welds of A7N01 alloy had deeper penetration than those of A5083 alloy In beads of A5083 alloy which has deeper penetration, the volume fraction of porosities was high due to the number of its was few, but size of its was larger. The case of deeper penetration beads of A7N01 alloy, the porosity reduced under relatively higher power The Volume fraction of porosities in weld of A5083 alloy was significantly higher than that in weld of A7N01 alloy.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.42-49
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• 2005

In general, multi-lap spot weld joints are frequently present in automobile. Most research, however, has been focused on the single-lap spot weld joints until now. In this paper, tensile-shear strength tests are performed to examine the weldability of 3-lap spot joint welded by using the high strength steel sheet and the zinc coated steel sheet. The indentation depth and nugget diameter are used to propose the optimum welding conditions. The weldability is affected by the welding current and welding time for 3-lap spot joint. Meanwhile the expulsions is round to decrease with the increase of electrode force. The optimum welding conditions are presented for 3-lap spot joints of high strength steel sheet and zinc coated steel sheet.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.72-81
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• 2011

In the present day, the needs of new steel for lightweight car-body have been increased in the automotive industry. however, the resistance spot welding is difficult to apply to the new steel because of the narrow weld current range and defects. As the solutions to these problems, adhesive bonding process is proposed. Adhesive bonding which reduce noise and vibration can be applied to joining the new steel. In this study, crash tests of b-pillar applied the resistance spot welding, structural adhesive bonding, the mixture of the structural adhesives and resistance spot welding were performed. And FEM crash model for b-pillar applied the structural adhesive bonding was developed. The results of experiment and analysis on b-pillar crash test were compared to verify the validity.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.192-199
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• 2000

The spot-welded automotive side member which has a hat-shaped section and a double hat shaped section has been tested on the axial static(10mm/min) and quasi-static(50mm/min) compressing load. The collapse characteristics of automotive sections have been reviews on shift on shape and in width of the spot-voiding on the flange. On the basis of the results of tests and reviews, the optimum energy absorption capacity of the structure has been studied.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.151-161
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• 1994

FCAW has wide application in ship fabrication, maintenance and field erection. It has many advantages over SMAW.SAW and GMAW process. In many applications, the FCAW provides highquality weld metal. This method can reduce weld defects especially porosity and spatter. But the fatigue characteristics of those deposited metal have been rarely investigated. The purpose of this study is to investigate the cyclic stress-strain behavior and fatigue tests by the constant strain control were carried out on the rounded smooth specimen with deposited metal using the metal type flux cored wire. As the results of this study for the deposited metal welded by the metal type flux cored wire, the hardening or softening characteristics under cyclic load were investigated and cyclic stress-strain curve, strain-fatigue life curve, stress-strain function and fatigue life relation which are useful to estimate the fatigue life under the stress concentration condition were obtained.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.1
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• pp.65-73
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• 1986

Surface fatigue crack propagation tests by plane bending fatigue were conducted on the welding specimens of an aluminium alloy, A5083-0, having an edge through thickness notch to study the fatigue crack growth characteristics. Moreover, the experiments were performed in order to clarify the fatigue crack initiation and growth. The properties of fatigue crack growth were quantitatively inspected in welded metal, heat-affected zone and base metal of the welding specimens. The main results obtained are summarized as follows: 1. It is found that the hardness distributions of A5083-0 aluminium alloy weldments are quite different with those of steel material weldments, so that the hardness distribution becomes lower in the following order: base metal, heat-affected zone and weld metal. 2. It is observed that the grain size of this specimen weldment appears to be almost equal to the base metal, when TIC welding method is adopted. 3. In a surface fatigue crack initiation and growth, the fatigue crack does not begin by opening-closing mechanism until hardening is saturated at the crack tip. 4. The fatigue crack growth characteristics of A5083-0 alluminium alloy weldments can be concluded.$${\frac{da}{dn}}=C({\Delta}K)^n=3.8{\times}10^{-9}{({\frac}{1}{2}{\Delta}S_t{\sqrt{{\pi}a}})}^{2.4}$$