• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1632-1642
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• 1992

When a blind hole of small diameter is drilled in the field of residual stress, strain relieved around the hole is function of magnitude of stress, patterns of stress distribution and hole geometry of diameter and depth. Relieved strain coefficients can be calculated from FEM analysis of relieved strain and actual stress. These relieved strain coefficients make it possible to measure residual stress which vary along the depth in the subsurface of stressed material. In this study, the calibration tests of residual stress measurement are carried out by drilling a hole incrementally on the cantilever or on the tensile test bar. Residual stresses can be determined from measured strains around a shallow hole by application of power series method. For the sake of reliable measurement of residual stress, much efforts should be done to measure relieved strains and hole depth more accurately comparing with conventional procedures of gage subject to the external load. Otherwise linear equations converting strains into stresses may yield erratic residual stresses because of ill-conditions of linear equations. With accurate measurements of relieved strains, residual stress even if varying along the depth can be measured. It is also possible to measure residual stress in the thin film of material by drilling a shallow hole.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.482-490
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• 1997

The effects of strain amplitude. test temperature and stress on the fatigue properties for Ti-Ni wires were investigated using a rotary bending fatigue tester specially designed for wires. The fatigue test results were discussed in connection with the static tensile properties. The DSC measurement was conducted after fatigue test in order to clarify the change of transformation behavior due to the progress of fatigue. Under the temperature below or near the Af, the strain amplitude($\varepsilon_a$)-failure life (Nf) curve showed to be composed of three straight lines with two turning points. Of the 2 turning points, the upper one was coincident with the elastic limit strain and the lower one with the proportional limit strain. With rising of the test temperature above Af, the pattern of $\varepsilon_a$-Nf curve changed gradually to composition of 2 straight lines. The $\varepsilon_a$-Nf curve shifted depending on test temperature. In the short and medium life zones, the higher the temperature was, the shorter the fatigue life. However, in the long life zone, above the Af temperature, the fatigue life was not affected by the temperature. The transformation enthalpy measured after fatigue test was dependent on Nf, $\varepsilon_a$, and test temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.54-62
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• 2019

In this paper, a stress-strain model for high-strength confined concrete is proposed using compressive fracture energy. In the compression test performed by author in Reference [6], an acrylic bar with strain gauges was embedded in the center of the specimen to measure the local strain distribution. It was found from the test that the local strain measurement by this acrylic rod is very effective. The local fracture zone length was defined based on the local strain distribution measured by the acrylic rod. Specifically, it was defined as the length where the local strain increases more than twice of the strain corresponding to maximum stress. In addition, the stress-strain relationship of confined concrete with compressive fracture energy is proposed on the assumption that the amount of energy absorbed by the compressive members subjected to the given lateral confining pressure is constant regardless of the aspect ratio and size. The proposed model predicts even results from other researchers accurately.

• International Journal of Railway
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• v.8 no.1
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• pp.1-4
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• 2015

An accurate measurement of the train-track interaction forces is important for track performance evaluation. In the field calibration test as a wheel load measurement process, the calibration system creates a different boundary condition in comparison with that in the train wheel passage. This study aims to evaluate a reliability of the field calibration test in the process of wheel load measurement. Finite element models were developed to compare the deformed shapes, bending moment and shear force profiles on the rail section. The analysis results revealed that the deformed shapes and their associated bending moment profiles on the rail are significantly different in two numerical simulations of the calibration test and the train wheel load passage. However, the shear stress profile on the rail section of the strain gauge installation in the field was almost identical, which may imply that the current calibration test is sufficiently reliable.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.66-71
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• 2003

The release of residual stress by mechanical loading and unloading is often performed in the fabrication of box structure fur steel bridge. The proper degree of loading and unloading is significant at release method of residual stress by mechanical loading because that degree is changed by material and geometric shape of welded structure. Therefore, the simulation model that could exactly analyze the release of residual stress by mechanical loading is to be necessary. In this study, the non-linear behavior of weldments under external loading and unloading, such as the decrease and increase of structure stiffness, was investigated by monitoring of nominal stress and strain. Tensile loading and unloading test and the proper degree of stress relaxation was measured by sectioning technique using strain gauge. Analysis model that is indispensable for the effective application of MSR method was established on the basis of test and measurement result.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.599-606
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• 2022

Strain gauges and the bridge weigh-in-motion (BWIM) method are the representative field measurement methods used for fatigue evaluationsof a steel bridge-in-service. For a fatigue reliability evaluation to assess fatigue damage accumulation, the effective stress range and the number of stress cycles applied as the fatigue details can be estimated based on the AASHTO Manual for Bridge Evaluations with the field measurement data of the target bridge. However, the procedure for estimating the effective stress range and the stress cycles from field measurement data has not been explicitly presented. Furthermore, studies that quantitatively compare differences in fatigue evaluation results according to the field measurement data type or processing method used are still insufficient. Here, a fatigue reliability evaluation is conducted using strain and BWIM data that are measured simultaneously. A frame model and a shell-solid model were generated to examine the effect of the accuracy of the structural analysis model when using BWIM data. Also, two methods of handling BWIM data when estimating the effective stress range and average daily cycles are defined. As a result, differences in evaluation results according to the type of field measurement data used, the accuracy of the structural analysis model, and the data handling method could be quantitatively confirmed.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.36-40
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• 2018

In this study, the electromechanical properties in Sn-Cu double layer stabilized GdBCO coated conductor (CC) tapes with and without external lamination under uniaxial tension were examined at 77 K and self-field. Their irreversible stress and strain limits were determined using a loading-unloading scheme based on different critical current ($I_c$) recovery criteria. The repeated tests were performed and statistical estimation was done to check the reproducibility depending on the criterion adopted in evaluating the electromechanical properties. From the results, it showed that the Sn-Cu double-layer stabilized CC tapes have the higher irreversible stress limit, but lower irreversible strain limit as compared to brass laminated ones. Through the repeated tests, it can be found that a small scattering of irreversible limits existed in both CC tape samples. Finally, similar strain sensitivity of $I_c$ in both CC tapes was obtained.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.71-77
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• 2011

Recently, non-destructive stress measurement method using magnetic anisotropy sensor has been applied to the construction site such as steel bridges and steel pipes. In addition, steel rib used in the tunnel construction site was found to be possible to measure the stress by non-destructive method. In this study, steel loading experiments using magnetic anisotropy sensor developed in Japan and strain gauges were conducted to derive stress sensitivity curve for domestic steel SS400. Also, additional steel loading experiments and numerical analysis were performed for evaluation of applicability for non-destructive stress measurement method using magnetic anisotropy sensor. As a result of this study, stress sensitivity curves for domestic steel SS400 were derived using output voltage measured by magnetic anisotropy sensor and average of stress measured by strain gauges depending on the measurement location. And as a result of comparing additional steel loading experiments with the numerical analysis, error level of magnetic anisotropy sensor is around 20MPa. When considering the level of the yield stress(245MPa) of steel, in case of using magnetic anisotropy sensor in order to determine the stress status of steel, it has sufficient accuracy in engineering. Especially, magnetic anisotropy sensor can easily identify the current state of stress which considers residual stress at steel structure that stress measurement sensor is not installed, so we found that magnetic anisotropy sensor can be applied at maintenance of steel structure conveniently.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.4
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• pp.180-184
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• 2020

The crystallographic texture plays an important role in both the plastic deformation and the macroscopic anisotropy of magnesium alloys. In previous study for AZ80 magnesium alloy, it was found that the main texture components of the textures vary with the deformation conditions at high temperatures. Also, the basal texture was formed at stress of more than 15-20 MPa and the non-basal texture was formed at stress of less than 15-20 MPa. Therefore, in this study, uniaxial compression deformation of AZ80 magnesium alloy was carried out at high temperature (stress of 15-20 MPa). The uniaxial compression deformation is performed at temperature of 723 K and strain rate 3.0 × 10^-3s^-1, with a strain range of between -0.4 and -1.3. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. EBSD measurement was also conducted in order to observe spatial distribution of orientation. As a result of high temperature deformation, the main component of texture and its development vary depending on deformation condition of this study.

• Journal of the Korean Institute of Gas
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• v.9 no.3 s.28
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• pp.27-31
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• 2005

The membrane to be applied inside of the LNG storage tank is provided with corrugations to absorb thermal contraction and expansion caused by LNG temperature and pressure changes. It is very important to measure their thermal strains under LNG temperature by analytical and experimental stress analysis of the membrane. We have developed a stress measurement system using strain gages and measured the strain during cooldown and storing the LNG. We also analyzed the measured data by comparison with the FEM data.