• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1059-1064
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• 2012

In this study, tensile tests were performed on specimens that simulated the cold-bending and heat-treatment of pipe bends to understand the mechanical properties of pipe bends manufactured by cold-bending followed by heat-treatment for relieving residual stress. The strength and ductility of cold-worked materials were respectively found to be higher and lower than those of the parent material although heat-treatment was carried out to relieve residual stress. In addition, the increase in strength and decrease in ductility were proportional to the applied strain levels for cold-working. It was thus inferred that the intrados and extrados regions of pipe bends that were cold-bended and heat-treated show higher strength and lower ductility compared to the parent straight pipe and that the mechanical properties at the crown region are nearly the same as those of the parent straight pipe.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.347-347
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• 2005

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.333-340
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• 2010

This paper presents the distributions of the tensile and fracture properties of an alloy 82/182 dissimilar weld joint between an SA508 Gr.3 nozzle and F316L SS safe-end at ambient temperature. Tensile and J-R tests were conducted using specimens extracted from base metals, heat-affected zones (HAZs), buttering regions, and various regions of the weld metal. The results show that the root region of the weld has higher strength than the upper region. The yield and tensile strengths vary considerably within the root region of the weld. The buttering region had the lowest strengths. The strengths gradually increased as the F316L stainless steel weld boundary was approached. The variation of the strengths within the upper region of the weld is insignificant. The fracture toughness of the alloy 82/182 weld metal is less than those of both the base metals and both HAZs. Within the alloy 82/182 weld, the center of weld has a slightly lower fracture toughness than the weld boundary and buttering region, and the root region has greater toughness than the upper region of the weld.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.655-662
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• 2014

This study conducted tensile tests on an Alloy 690TT tube at room temperature (RT) and at $343^{\circ}C$ using tube- and ring-type specimens to investigate the stress-strain behavior and tensile properties of a steam generator (SG) tube in the axial and circumferential directions at RT and at the design temperature of a nuclear power plant (NPP). The results of the axial tensile test showed that yield point phenomena appeared at both RT and $343^{\circ}C$, and serrated flow in the stress-strain curve appeared at $343^{\circ}C$. Yield and tensile strengths for both directions were clearly lower at $343^{\circ}C$ compared to RT; however, the elongations were approximately the same at both test temperatures. Regardless of the test temperature, the strengths in the circumferential direction were lower by approximately 5~10 % than those in the axial direction. In addition, the test data revealed that the reduction in the yield and tensile strengths of the Alloy 690TT SG tube with the test temperature was more significant than that estimated by the temperature correction factor of ASME Sec.II.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.70-70
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• 2007

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.455-467
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• 2001

In this study, the stacking phase shift effect on the effective property and stress distribution was investigated for 8-harness satin weave textile composites under uni-axial tension. Textile configurations with varied phase shifts were modeled by unit cells and repeating boundary conditions were applied at the outer periodic surfaces. The effective property and stress were calculated by the unit cell analysis using macro-element to reduce the computational resource. It was found that stresses were dependent on the variation of tow arrangement of adjacent layers. The in-phase and the shifted configurations showed large differences in the stress distribution pattern. The stress level was very high in the resin region and the distribution of the maximum stresses was widely scattered.

• Composites Research
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• v.13 no.6
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• pp.63-72
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• 2000

In this paper, statistical treatments of effective properties for plain weave textile composites were presented. Configurations up to 32 layers with varied stacking phase shifts were considered. Effective properties were calculated by numerical simulation in which uni-axial tensile and shear load were applied at unit cell. Sample analysis was utilized to consider the inherent randomness in the phase shift and the results were treated statistically. It was found that effective properties were dependent on stacking phase shifts for thin plain weave textile composites. The distribution of $E_{xx}$ and $V_{xy}$ were skewed and the range of possible values was relatively large. As the number of layers increased, however, the distribution width became narrower and mean values converged. In contrast, $G_{xy}$ was not affected by phase shifts and thickness changes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.41-52
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• 2003

In this paper, three-dimensional thermo-mechanical properties of carbon-phenolic 8-hamess satin weave composites were predicted considering geometric parameters of microstructures. The effective properties were calculated by a series of numerical experiments based on unit cell analysis. The microstructural details were modeled through macro-elements, and the periodic boundary conditions were derived for corresponding un it cell types. The Monte Carlo method was employed to consider the random phase shift between the layers, and the results were investigated on the effect of the geometric parameters of shift, number of layers and waviness ratios. Experimental tests were also performed and the results were compared.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.73-80
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• 2008

Experimental study has been performed in order to construct the standard test methods and appraisal criteria by investigating the influence of specimen types(property, width, layers) and loading rate on the tensile characteristics of FRP used in strengthening RC structures. The FRP composite tested in this study are the unidirectional CFRP sheet/strip and the bidirectional GFRP sheet. Test variables consist of the various width ranging from 10mm to 25mm and number of CFRP sheets plied up to 5 layers. Test results indicated that maximum tensile strength and minimum coefficient of variation are recorded at each different width according to the fiber types and weaving directions. Also, the average tensile strengths of CFRP sheets are decreased as the number of layer of CFRP sheet are increased.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.734-739
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• 2008

In this study, the nonlinear mechanical behavior of flexible textile composites was predicted by two-step analyses: micromechanics and mesomechanics. The effective material properties for fiber tows of flexible textile composite lamina were calculated in micromechanics, which were then used to calculate the effective tensile stress-strain curve of flexible textile composites in mesomechanics. A user defined material algorithm was developed and inserted in ABAQUS to account for the geometric non-linearity due to the large rotation and shear deformation of fiber tows in mesomechanics. It was found that the stress-strain behavior of flexible textile composites exhibited significant non-linearity. The effective tensile modulus agreed well with the test result.