• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.9-12
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• 2008

The residual stress induced in the superconducting layer was estimated using analytical approach coupled with electro-mechanical test results and XRD measurements. The residual stress measured based on the $I_{c}/I_{c0}$-strain degradation behavior showed similar value with the measured residual stress using XRD. The calculated residual stress based on the thermal analysis showed the lowest value. This could be explained by the additional intrinsic residual stresses induced in the superconducting film during deposition.

• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.12-16
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• 2009

The laminated sequence and thickness of a composite structure is an important design parameter which affect the strength and impact damage. In this study, it was investigated the residual strength of carbon fiber laminate after impact damage by the experimental investigation. The tensile strength test and compressive strength test were used to find the mechanical properties, previously. Impact test was performed using low-velocity drop-weight test equipment. The impact damages were finally assessed by the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the impact damage.

• Communications for Statistical Applications and Methods
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• v.22 no.5
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• pp.495-506
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• 2015

Volatility is a variation measure in finance for returns of a financial instrument over time. GARCH models have been a popular tool to analyze volatility of financial time series data since Bollerslev (1986) and it is said that volatility is highly persistent when the sum of the estimated coefficients of the squared lagged returns and the lagged conditional variance terms in GARCH models is close to 1. Regarding persistence, numerous methods have been proposed to test if such persistency is due to volatility shifts in the market or natural fluctuation explained by stationary long-range dependence (LRD). Recently, Lee et al. (2015) proposed a residual-based cumulative sum (CUSUM) test statistic to test volatility shifts in GARCH models against LRD. We propose a bootstrap-based approach for the residual-based test and compare the sizes and powers of our bootstrap-based CUSUM test with the one in Lee et al. (2015) through simulation studies.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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• pp.84-90
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• 2004

For the precise assessment of the effect of welding residual stresses on structural strength and fatigue crack growth behavior, new FE analysis algorithms for the estimation of residual stress relaxation due to external load and redistribution due to fatigue crack propagation were proposed in this paper. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis In the analysis of fatigue crack propagation, the applied SIF(Stress Intensity Factor) range was evaluated by $\frac{1}{4}$-point displacement extrapolation method, and the effect of welding residual stresses on crack propagation was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.25-30
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• 2003

The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI). The residual stress fields in case of both single and film/substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 ${\mu}m$ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the x-ray diffractometer (XRD) for the verification of above residual stress results by ESPI.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.253-257
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• 2016

The effects of re-peening on the compressive residual stress and fatigue life of Al7075-T6 were investigated. The compressive residual stress induced on the surface of components by shot peening is known to increase the fatigue life. However, the fatigue load relaxes the compressive residual stress of components. Re-peening is a technique to again induce the relaxed compressive residual stress and increase the total fatigue life of components. In this study, the re-peening process was applied to fatigue-loaded specimens. The compressive residual stress and fatigue life were examined for re-peened specimens with fatigue ratios of 30%, 50%, and 70%. The results showed that the compressive residual stress of the specimens was relaxed under the fatigue load. The re-peening process significantly increases the compressive residual stress and total fatigue life.

• Steel and Composite Structures
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• v.17 no.2
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• pp.173-184
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• 2014

This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.245-247
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• 2002

The paper represents the effects of the drive-in process parameters on the residual stress profile of the p+ silicon film. For the quantitative determination of the residual stress profiles, the test samples are doped via the fixed boron diffusion process and four types of the thermal oxidation processes and consecutively etched by the improved process. The residual stress measurement structures with the different thickness are simultaneously fabricated on the same silicon wafer. Since the residual stress profile is not uniform along the direction normal to the surface, the residual stress is assumed to be a polynomial function of the depth. All of the coefficients of the polynomial are determined from the deflections of cantilevers and the displacement of a rotating beam structure. As the drive-in temperature or the drive-in time increases, the boron concentration decreases and the magnitude of the average residual tensile stress decreases. Also, near the surface of the p+ film the residual tensile stress is transformed into the residual compressive stress and its magnitude increases.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.484-490
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• 2021

Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.

• Journal of the Korean Geotechnical Society
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• v.35 no.5
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• pp.43-51
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• 2019

At present, the ground anchor method is commonly applied to securing the slope stability in Korea. The ground anchor is reported to decrease in tensile load due to aging and environmental influences with time such as corrosion, relaxation, creep and so on. In Korea, the lift-off test is performed for the periodic inspection or cases when the symptoms of deterioration on anchors and the residual tensile load of the anchors is checked. However, the current lift-off test standard (MOLIT, 2010) is not fully specified in details. In this study, the factors affecting the lift-off test were investigated based on the previous research and foreign standards and lift-off tests were performed with consideration for the loading and unloading cycle, load increment method, and tensioning tendon method. Based on the results, this paper proposes improved testing and evaluation procedures of the lift-off test considering the workability and time limits in the field.