• Journal of Welding and Joining
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• v.10 no.4
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• pp.250-258
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• 1992

In order to clarify the mechanical behavior of welding crack and to evaluate the mechanical characteristics of welded parts in thick plate, it is very important to accurately predict the welding deformation and residual stress including transient state before welding. In this paper, the theory of a three-dimensional elasto-plastic problem for the analysis of mechanical phenomenon of welding joint on the plate is developed into an efficient and accurate method based on the finite element method, and then several examples are considered by using the proposed model. The results of numerical analyses are discussed in the viewpoint of the mechanical characteristics of the distribution of three-dimensional welding residual stresses, plastic strains and their production mechanism on the thick plate.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.115-123
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• 1997

The buckling strength, fatigue strength, stress corrosion cracking are considerably effected on one of initial imperfections, the residual stresses produced by a circumferential weld between axisymmetric cylinders. Therefore, we study the residual stresses, plastic strain and temperature distribution with using thermal elasto-plastic analysis which are generated by a circumferential weld between axisymmetric cylinders. It is investigated that welding residual stresses have an effect on the strength of cylinder for inner and outer shell under external pressure.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.6-9
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• 2012

• Journal of Welding and Joining
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• v.26 no.4
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• pp.14-20
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• 2008

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.505-510
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• 2002

The Friction Stir Welding (FSW) is a new joining method that was developed at The Welding Institute (TWI) in England in 1991. It applied heating by the rotational friction and material plastic flow. It was developed as a new joining method to solve the problems of epochally in the welding of Al alloys. In the study, 6000series of Alloy composed of AI-Mg-Si, one of the Al alloys that are utilized for shipbuilding and construction, is selected as a specimen and the numerical is executed against the welded zone of FSW. The material used in this study had the unique properties of strength and anti-corrosion, but since the welded joint of this material is easily softened by the welding heat, FSW is executed and the numerical analysis is carried out around the joint. To examine the mechanical behaviors and properties, F.E.M analysis is executed and the developed thermal-elastic-plastic [mite analysis are used.

• Journal of Welding and Joining
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• v.6 no.4
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• pp.35-43
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• 1988

Welding residual stresses were calculated by two dimensional thermal elasto-plastic analysis using element method. Complicated plastic behavior during heat transfer was simulated with time. Fist, temperature distributions. To consider time varying behavior of material properties and loading and unloading processes, iterative calculation based on initial stiffness method was carried out. The method proposed by Yamata was used in time increment control which determined the accuracy of claculation. comparison with other caculated and experimental results shows fairly good agreement.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.83-88
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• 2000

Variation of welded-joint hardness and tensile strength of a accelerated-cooled fine-grained ferritic-pearlitic steel with heat input was investigated. In a weld heat-affected zone, a softened zone was formed and it had lower hardness than that of a base metal. While the width of a softened zone increased continuously with an increase of heat input up to 100kJ/cm. the minimum hardness in a softned zone was almost constant after a continuos decrease up to 60KJ/cm. Because of a softened zone, the welded-joint was fractured in the HAZ and its maximum reduction of tensile strength was about 20%. Measured welded-joint tensile strength and calculated minimum tensile strength in a welded-joint was almost same, which means that the plastic restraint of a softened zone did not occur in this experiment. It is believed that as a softened zone width-to-specimen thickness ratio is as high as 2~6 in this experiment, the plastic restraint effect does not occur. Theoretical analysis shows that the plastic restraint effect occurs only when the ratio is below 0.5.

• Journal of Welding and Joining
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• v.2 no.1
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• pp.41-48
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• 1984

Recrystallization technique was applied to analyze plastic strain at the notch tip of coarse grain HAZ in mild steel (SB 41) and high strength steel (SA 588). The notch tip of specimen was deformed by three point bending. Accumulated displacement (Crack Opening Displacement ${delta}t$) by the monotonic and cyclic loading under room temperature and hot strain embrittlement temperature ($250^{\circ}C$) was 0~1.0mm. Recrystallization heat treatment conditions were $650^{circ}C{ imes}3hr$ for SB 41 and $700^{circ}C{ imes}3hr$ for SA 588. The experimental results obtained were as follows ; 1) Distribution of the effective plastic strain at plastic zone was appeared by the function of crack opening displacement, and plastic zone or the effective plastic strain increased with crack opening displacement. 2) Plastic strain at notch tip of HAZ due to accumulated hot strain calculated as follows. .epsilon. over bar $_{p}$ = .epsilon. over bar $_{cr}$ (x/ $R_{x}$ ) $^{m}$ (m=0.25) 3) Work hardending ratio of notch tip for hot strain was linearly increased with .epsilon. over bar $_{max}$ and dependent upon the material types.s.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.288-289
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• 2004

In this report, stress analysis of restraint specimen was done by numerical method (finite element method). Calculations were done by elastic-plastic analysis and thermo-elastic-plastic analysis. The results showed similarities for both cases, and by thermo-elastic-plastic analysis transient characteristics of welding could be found.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.131-135
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• 2003

The form-joining process (or clinching) uses a set of die and punch to impose the plastic deformation-induced geometric constraint on a sheet metal pair, But their joining strength ranges 50-70 percent of that of the resistance spot welding. In this paper, a new form-joining process with the aid of adhesive is proposed in which an epoxy adhesive is applied to a sheet metal pair, to improve joining strength. The strength and mechanical properties of the new process are discussed and compared for other joining processes.