• Journal of Welding and Joining
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• v.21 no.6
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• pp.40-45
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• 2003

Steel members have advantages of resisting torsion and axial compression. In design, residual stresses at the welded joint of T-shape steel pipes are one of the most important points to be considered. In this paper, characteristics of residual stresses of welded joints are clarified by carrying out 3D non-steady heat conduction analysis and 3D thermal elastic-plastic FE-analysis. According to the results, the production mechanism of residual stresses at the welded joint of T-shape steel pipe is clarified. In this paper, circumferential stresses depended on thermal histories but axial and radial stresses were more dependent on geometrical shape than thermal histories. Residual stresses in the axial direction on the lower part of pipe member were tensile, controlled by geometrical shape. However, in case of middle part, residual stresses in all the directions were controlled by thermal histories.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.279-289
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• 2000

Residual stress induced in U-bending and tube-to-tubesheet joint processes of PWR's row-1 heat exchanger tube was measured by X-ray method and Hole-Drilling Method(HDM). Compressive residual stresses(-) at the extrados surface were induced in U-bending, and its maximum value reached -319 MPa in axial direction at the position of $\psi$ = $0^{\circ}$. Tensile residual stresses(+) of $\sigma_{zz}$ = 45 MPa and $\sigma_{\theta\theta}$ = 25 MPa were introduced in the intrados surface at the position of $\psi$ = $0^{\circ}$. Maximum tensile residual stress of 170 MPa was measured at the flank side at the position of $\psi$ = $90^{\circ}$, i.e., at apex region. It was observed that higher stress gradient was generated at the irregular transition regions (ITR). The trend of residual stress induced by U bending process of the tubes was found to be related with the change of ovality. The residual stress induced by the explosive joint method was found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the transition region (TR), and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.101-107
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• 2008

A composite mechanics for discontinuous fiber reinforced polymer matrix composites(PMC) is analysed in order to predict fiber axial stresses. In continuum approach. frictional slip which usually takes place between fibers and polymers is accounted to derive PMC equations. The interfacial friction stress is treated by the product of the coefficient of friction and the compressive stress norma1 to the fiber/matrix interface. The residual stress and the Poisson's contraction implemented by the rule of mixture(ROM) are considered for the compressive stress normal to the fiber/matrix interface. In addition. the effects of fiber aspect ratio and fiber volume fraction on fiber axial stresses are evaluated using the derived equations. Results are illustrated numerically using the present equations with reasonable materials data. It is found that the fiber axial stress in the center region shows no great discrepancy for different fiber aspect ratios and fiber volume fractions while some discrepancies are shown in the fiber end region.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.57-65
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• 2000

The stress corrosion crack growth is simulated assuming a small axial surface crack inside a S/G tube. Internal pressure and residual stresses are considered as applied forces. Stress intensity factors along crack front, variation of crack shape and crack growth rate are obtained and discussed. It is noted that the aspect ratio of the crack is not depend on the initial crack shape but depend on the residual stress distribution.

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.7-13
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• 2009

The objective of this study is to design a laboratory specimen for simulating residual stress of circumferential butt welding between pipes. Specimen type and method to generate residual stress were proposed based on the review of prior studies and parametric finite element analysis. To prove the proposed specimen type and loading method, the residual stress was generated using the designed specimen by applying proposed method and was measured. The measured residual stress using X-ray diffraction reasonably agreed with the results of finite element analysis considered in the specimen design. Comparison of residual strains measured at several locations on the specimen and given by finite element simulation also showed good agreement. Therefore, it is indicated that the designed specimen in this study can reasonably simulate the axial residual stress of a circumferential butt welding of pipe.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.163-169
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• 1999

Residual stresses causing stress corrosion cracking (SCC) of thin-walled steam generator U tubes were investigated. The residual stresses were measured by hole drilling methods, and the applied stresses resulting from the internal pressure and the temperature gradient in the steam generator were estimated theoretically. In U-bent regions, the residual stresses at extrados were induced with compressive stress(-), and its maximum value reached -319MPa in axial direction at $\phi$= $0^{\circ}$ in position. Maximum tensile residual stress of 170MPa was found to be at the flank side at position of $\phi$= $90^{\circ}$, i.e., at apex region. Hoop stress due to the pressure and temperature differences between primary and secondary side were analyzed to be 76 MPa and 45 MPa, respectively.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.8 no.1
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• pp.19-24
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• 2012

This paper presents the results of finite element analysis for the effects of hydrostatic test and operating condition on the weld residual stress at dissimilar metal weld of a pressurizer safety nozzle in a nuclear power plant. For the study, the weld residual stress at ambient condition was analyzed using ABAQUS in the first place. After the weld residual stress analysis, the hydrostatic test condition and operating condition was applied to the same model one after another. The weld residual stress was observed to change due to the successive hydrostatic test and operating condition. The axial residual stresses on inner surface of the dissimilar metal weld and HAZ region were decreased by hydrostatic test and operating condition, which gives beneficial effect on preventing primary water stress corrosion cracking.

• Transactions of Materials Processing
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• v.14 no.8 s.80
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• pp.704-711
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• 2005

The influence of process parameters in drawn wire on residual stresses was investigated. Based on a FE-simulation of the wire drawing process, the effects of process parameters such as semi-die angle, reduction, friction coefficient and bearing length on the residual stresses were investigated. The validity of the FE-simulation results was verified by the comparison of the previous simulated results with experimental data. In this study, semi-die angle and die reduction have significant effect on the residual stresses at the surface of drawn wire. Several methods such as, addition of axial tension, application of skin pass, straightening in multi-roll straightener etc, were suggested in the previous studies to reduce the residual stresses. In this study, the results show that the concurrent application of skin pass with low die reduction and low semi-die angle at the final stage of drawing operation reduces dramatically the both axial and hoop residual stresses after drawing

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1384-1392
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• 2002

Single fiber pull-out technique has been commonly used to characterize the mechanical behavior of interface in fiber reinforced composite materials. An improved analysis considering the effects of transversely isotropic properties of fiber and the effects of thermal residual stresses in both radial and axial directions along the fiber/matrix interface is developed for the single fiber pull-out test. Although the stress transfer properties across the interface is not much affected by considering the transversely isotropic properties of fiber, interfacial debonding is notably encouraged by the effect. The interfacial shear stress that plays an important role in interfacial debonding is very much affected by the component of axial thermal residual stress in the bonded region, which can induce a two-way debonding mechanism.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.834-837
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• 2005

This study presents a study on the influence of process parameters(semi-die angle, die reduction, friction condition, and bearing length) in drawn wire on residual stresses were investigated using FE-analysis. In this study, semi-die angle and die reduction have a significant effect on the residual stresses at the surface of drawn wire. In the previous study, in order to reduce the residual stresses, several methods were suggested: addition of axial tension, application of skin pass, straightening in multi-roll straightener etc. In this study, it can be known that the concurrent application of skin pass with low die reduction and low semi-die angle at the final stage of drawing operation reduces dramatically the both axial and hoop residual stresses after drawing.