• Nuclear Engineering and Technology
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• 제47권1호
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• pp.115-125
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• 2015

Background: Residual stress always exists on any kind of welded area. This residual stress can cause the welded material to crack or fracture. For many years, the hole-drilling method has been widely used for measuring residual stress. However, this method is destructive. Nowadays, electronic speckle pattern interferometry (ESPI) can be used to measure residual stress with or without the hole-drilling method. ESPI is an optical nondestructive testing methods that use the speckle effect. Mechanical properties can be measured by calculation of the phase difference by the variation of temperature, pressure, or loading force. Methods: In this paper, the residual stress on the butt-welded area is measured by using ESPI with a suggested numerical calculation. Two types of specimens are prepared. Type I is made of pure base metal part and type II has a welded part at the center. These specimens are tensile tested with a material test system. At the same time, the ESPI system was applied to this test. Results: From the results of ESPI, the elastic modulus and the residual stress around the welded area can be calculated and estimated. Conclusion: With this result, it is confirmed that the residual stress on the welded area can be measured with high precision by ESPI.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.481-482
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• 2007

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1347-1356
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• 2024

Measuring the residual stress in the components in nuclear power plants is crucial to their safety evaluation. The instrumented indentation technique is a minimally invasive approach that can be conveniently used to determine the residual stress in structural materials in service. Because the indentation behavior of a structure with residual stresses is closely related to the elastic-plastic behavior of the indented material, an accurate understanding of the elastic-plastic behavior of the material is essential for evaluation of the residual stresses in the structures. However, due to the analytical problems associated with solving the elastic-plastic behavior, empirical equations with limited applicability have been used. In the present study, the impact of the non-equibiaxial residual stress state on indentation behavior was investigated using finite element analysis. In addition, a new nonequibiaxial residual-stress prediction methodology is proposed using a convolutional neural network, and the performance was validated. A more accurate residual-stress measurement will be possible by applying the proposed residual-stress prediction methodology in the future.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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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.

• 비파괴검사학회지
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• 제14권1호
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• pp.7-15
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• 1994

동을 중간재로 하는 $Si_3N_4/SUS304$ 접합재의 접합계면 근방의 잔류응력 분포를 유한요소법과 X선 응력측정법을 이용하여 해석을 하였다. 그 결과, 접합재의 세라믹부 계면 근방의 잔류응력 분포를 정량적으로 밝혀낼 수 있었다. 세라믹부에 발생되는 접합 잔류응력은 접합계면 근방에서 대단히 크게 나타났으며, 특히 최대인장 잔류응력 ${\sigma}_x$는 단부에서 발생하였다. 한편, ${\sigma}_x$는 접합계면 근방에서 3차원분포를 하고 있기 때문에 2차원 유한요소 해석결과와는 대단히 다른 값을 나타내고 있으며, 특히 시험편 중앙부의 계면 근방에서는 X선 실측결과가 인장 잔류응력임에 반하여 2차원 유한요소 해석결과는 압축 잔류응력으로 계산되어짐을 알았다. 따라서, 이와같은 3차원 분포를 하고 있는 접합계면 근방의 잔류응력 ${\sigma}_x$보다 간편하고 정확하게 예측할 수 있는 유한요소 해석모델에 대하여 서로 검토하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.331-332
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• 2002

Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses of the high hardness steel (over $H_{RC}60$) workpiece (SKD11) machined by the hard turning were measured using Hole-drilling Method. Residual stress in the surface of hard turned workpiece was mainly appeared to be compressive stress.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.134-137
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• 2008

The effects of residual stress and surface defects on the mechanical properties of the high carbon steel filament used for the automotive tire have been experimentally investigated. The samples were fabricated with annealing temperature. The residual stress was measured by focused ion beam and strain mapping software which has advantages, such as data with high accuracy and fast data acquisition time. Mechanical properties, such as tensile strength and fatigue resistance, were gradually increased up to $200^{\circ}C$ and then slightly decreased. From the measurement of residual stress and level of surface defect, it was revealed that the critical factor was varied with different temperature region. That is, the fatigue resistance increased due to decreasing the residual stress and decreased due to increasing the size and distribution of surface defect.

• 한국정밀공학회지
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• 제17권12호
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• pp.195-200
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• 2000

In order to find a residual stress in the micro-machined beam, first natural frequency of the beam that has the residual stress inside is analyzed using the Rayleigh's energy method. Micro gold electroplated structure is fabricated by surface micro-machining process. The made structure is clamped-clamped beam and its 1st natural frequency is measured by resonance method. For the better estimation of the residual stress, an equivalent length of micro-machined beam to ideal beam is calculated by FEM. The residual stress is estimated from the equivalent length and the measured natural frequency.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.150-152
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• 2004

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.1007-1009
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• 1998

In this paper, the effects of the drive-in process parameters on the residual stress profile of the p+ silicon film has been investigated. All the residual stress profile has been estimated by the second-order polynomial. All the coefficients of the polynomial have been determined from the measurement of the deflections of cantilevers and a rotating beam by using a surface profiler meter and by means of focusing a calibrated microscope. As the drive-in temperature or the drive-in time increases, the boron concentration decreases and the magnitude of the average residual stress decreases. If the boron concentration decreases the tensile residual stress decreases except near the surface where the magnitude of compressive residual stress increases.