• Journal of Korean Society of Steel Construction
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• v.16 no.4 s.71
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• pp.479-492
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• 2004

When U-ribs of steel deck plates are connected at the field, overhead welding should be done with backing strips. Misalignments may occur and lead to eccentric moments as well as high stress concentrations at welded joints. In this study, stress analyses and fatigue tests were carried out. Stress analyses for U-ribs' welded joints with backing strips were performed with different misalignments, root shapes, root gaps, and backing strip sizes. From the stress analyses, the stress concentration factors increased with increasing misalignments and root gaps. With the fixed misalignments and root gaps, the stress concentration factors obtained in the case of the semi-circle root shape were lower than those in the case of the right-angle root shape. It was verified that backing strip sizes have little influence on stress concentration factors. The fatigue tests for U-ribs' welded joints with backing strips indicated that increased misalignments shorten fatigue life drastically and cracks usually initiate at the root of the base metal and are propagated to the weld bead surface. Based on the results of the stress analyses, root-shape control methods were developed to mitigate stress concentration by changing welding condition control, radius curvature, and flank angle.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.133-141
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• 2002

Isotropic rock and anisotropic rock have different tensile strength which has the greatest influence on rock failure. In this study, elastic modulus of anisotropic rock is obtained through uniaxial compression test, and tensile strength and tension failure behavior are analyzed through indirect tensile strength test. Stress concentration factor of a specimen at the center is obtained from anisotropic elastic modulus and strain by indirect tensile strength test. Theoretical solutions for tensile strength of isotropic and anisotropic rock are compared. Stress concentration factor of anisotropic rock is either higher or lower than isotropic rock depending on the inclination angle of bedding plane. The use of stress concentration factor of isotropic rock resulted in overestimation or underestimation of tensile strength.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1163-1169
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• 2014

In this study, a fatigue assessment method for vehicle suspension systems having welded geometries was established under a bending loading condition. For the fatigue life estimation of the actual product's welded joints made of different steels, bending fatigue tests were performed on welded specimens with a simplified shape for obtaining the moment-fatigue-life plot. Further, geometry modeling of the simplified welded specimens was conducted. Results of finite element analysis were used to obtain the stress-fatigue-life plot. The analysis results were also used to calculate the stress concentration factors for notch-factor-based fatigue life estimation. The test results were compared with results of the general notch-factor-based fatigue life estimation for improving fatigue assessment. As a result, it was concluded that both the welded fatigue tests and the notch-factor-based fatigue life estimation are necessary for accurate fatigue assessment.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.85-93
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• 2012

In this study, the geometry of the weld is used to develop the process of fatigue life prediction. For the development of fatigue life prediction process, bending fatigue test of muffler is conducted to obtain M(Moment)-N(Fatigue life) diagram. Modeling the geometry of the weld which is failed is performed to conduct static load analysis and analysis results are used to calculate the stress concentration factor. The stress concentration factor is used to get the fatigue notch factor and this was based on the fatigue life prediction. As a result of the comparison of test values and predicted values, predicted values are verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.167-175
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• 2014

If volumetric flaws such as bearing pad fretting flaws and debris fretting flaws are detected in the pressure tubes of pressurized heavy water reactors during in-service inspection, the initiation of fatigue cracks and delayed hydrogen cracking from the detected volumetric flaws shall be assessed by using elastic stress concentration factors in accordance with CSA N285.8-05. The CSA N285.8-05 presents only an approximate formula based on linear elastic fracture mechanics for the debris fretting flaw. In this study, an engineering formula considering the geometric characteristics of the debris fretting flaw in detail was derived using two-dimensional finite element analysis and Kinectrics, Inc.'s engineering procedure with slight modifications. Comparing the application results obtained using the derived formula with the three-dimensional finite element analysis results, it is found that the results obtained using the derived formula agree well with the results of the finite element analysis.

• Journal of the KSME
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• v.34 no.11
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• pp.830-835
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• 1994

화재에 의해 손상을 입은 압력용기에 대해 유한요소법을 이용하여 응력해석을 수행하여 아래와 같은 결론을 얻었다. (1) 응력해석 결과, 압력용기의 자중, 열응력 및 바람의 영향은 내부압력에 비해 무시할 수 있을 정도로 미미하였다. (2) 기하학적 형상변화가 발생한 손상용기의 손상 부위에서의 부식 전\ulcorner후에서의 안전계수는 각각 3.5와 2.1로 손상이 없는 단순용기의 6.3과 4.6보다 상당히 작음을 알 수 있었다. 따라서, 손상 부위에서의 적절한 보강이 이루어져야 할 것이다. (3) 원형 링과 수직 보조대로 보강된 보강용기 모형의 등가 응력값은 상당히 감소되어 화재로 발생한 기하학적 형상 변화에 따른 응력 집중을 줄일 수 있었다. 앞서 정의된 안전계수를 이용 하면 부식 전의 안전계수는 5.3, 부식 후는 3.8 이상으로 증가하였다. (4) 안전계수는 운전 중의 부식 진행과 더불어 두께에 반비례하여 감소하므로, 운전중 부식의 진행을 억제 또는 최소화할 수 있는 방법이 강구되어야 하겠다. (5) 복구방안으로 본 연구에서 해석된 보강책을 채택하는 경우, 작업시 보조대 주위에서의 잔류 응력이 발생되지 않도록 특히 유의해야 하며, 복구 작업 후 철저한 시험검사(비파괴 검사, 스트 레인 측정)가 수반되어야 할 것으로 사료된다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.188-192
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• 1996

재결정 Zircaloy-2의 요드에 의한 응력부식균열의 전파속도를 직류전압강하측정법 (DCPD, Direct Current Potential Drop)을 이용하여 측정하고 임계응력집중계수( $K_{ISCC}$)를 구하였다. 임계요드농도 이상인 0.01 MPa의 요드농도에서, $K_{ISCC}$는 300 $^{\circ}C$의 경우 약 15 MPa√m, 350 $^{\circ}C$의 경우 약 12 MPa√m의 응력계수였으며, plateau 구역에서의 균열속도는 $10^{-4}$~ $10^{-3}$ mm/sec 영역이었다.

• Geotechnical Engineering
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• v.14 no.1
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• pp.93-108
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• 1998

In this study, the analytic solutions and numerical methods were used to estimate the shape and size effects on the stability of underground openings. The stability of underground openings was evaluated by scrutinizing the effects of the rock mass quality, the state of in-situ stresses and the lateral earth pressure coefficient on the displacement, the stress concentration and the plastic region developed in the vicinity of the openings. The analytic solutions have shown that the stress concentration factor is inversely proportional to the radius of curvature of openings. Through parametric study on the various shapes and sizes of underground openings the characteristics of the controlling factors concerned with the stability were analyzed. Then, the study was extended to the horseshoe-shaped openings commonly used for under ground storage. Through the extended study the effects of the stress ratio and the height-towidth ratio of openings on the maximum displacement and plastic region developed around the openings were estimated. The results have shorn that the height-to-width ratio of domestic storage caverns can be increased economically without stability problem, as far as the lateral earth pressure coefficient is appropriate.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.2
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• pp.437-444
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• 2017

Stress concentrations around discontinuities, such as a hole in cross section of a structural member, have great importance because the most materials failure around the region may be occurred. Stress on the point applied by concentrated load reaches much larger value than the average stress in structural member. In this paper, stress analysis was performed for the plate with a partial through-hole to find the difference of the principal stress distribution. The difference between maximum principal stress and minimum principal stress in photoelasticity is equal to the value obtained by multiplying the isochromatic fringe order by the fringe constant of the material divided by the distance through which the light passes, that is, the thickness of the specimen. Since the difference of principal stress is proportional to the photoelastic fringe order, the distribution of the principal stress difference by the finite element analysis can be compared with the photoelasticity experimental result. ANSYS Workbench, that is the finite element software, is used to compute the differences of principal stresses at the specific points on the measured lines. The computation values obtained by ANSYS are compared with the experimental measurements by photoelasticity, and two results are comparable to each other. In addition, the stress concentration factor is obtained using the stress distribution analyzed from the variation of hole depth. Stress concentration factor is increasing, as the depth of hole increase.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.5 no.2
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• pp.207-214
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• 2015

Stress concentrations around discontinuities, such as a hole or a sudden change in cross section of a structural member, have great important cause in the most materials failure because the stress near the points of application of concentrated loads can reach values much larger than the average value of the stress in the member. This paper presents the stress concentrations between fillet and hole at different locations in a stepped plate under tensile loading. The analysis for interaction effect of stress concentration was performed by photoelasticity and ANSYS which is a commercial finite element software. From the analysis results, the circular hole located at the different position from the fillet radius can cause different values of stress concentration factor within interacting region.