• Title, Summary, Keyword: 응력확대계수

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Three-Dimensional Virtual Crack Closure Technique Based on Anisoparametric Model for Stress Intensity Factors of Patch Repaired Plates with Cracks at Notches (접착 보강된 노치 균열판의 응력확대계수 산정을 위한 비등매개변수 모델 기반의 3차원 가상균열닫힘법)

  • Ahn, Jae-Seok;Woo, Kwang-Sung
    • Journal of The Korean Society of Civil Engineers
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    • v.32 no.1A
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    • pp.39-48
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    • 2012
  • This study deals with numerical determination of stress intensity factors of adhesively patch-repaired plates with cracks at V-shaped or semicircular notches. The p-convergent anisoparametric model are considered and then three-dimensional virtual crack closure technique is presented using formulations of anisoparametric elements. In assumed displacement fields of an element, strain-displacement relations and three-dimensional constitutive equations are derived with three-dimensional hierarchical shape functions expanded from one-dimensional Lobatto functions. Transfinite mapping technique is used to represent a circular boundary. The present model provides accuracy and simplicity in terms of stress concentration factor, stress distribution, the number of degrees of freedom, and non-dimensional stress intensity factor as compared with previous works in literatures. Stress intensity factors obtained by the three-dimensional virtual crack closure technique are estimated with respect to the variation of width of finite plate, radius of notch root, angular inclination of V-shaped notch, and crack length.

Reliability Estimation for Crack Growth Life of Turbine Wheel Using Response Surface (반응표면을 사용한 터빈 휠의 균열성장 수명에 대한 신뢰성 평가)

  • Jang, Byung-Wook;Park, Jung-Sun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.4
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    • pp.336-345
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    • 2012
  • In crack growth life, uncertainties are caused by variance of geometry, applied loads and material properties. Therefore, the reliability estimation for these uncertainties is required to keep the robustness of calculated life. The stress intensity factors are the most important variable in crack growth life calculation, but its equation is hard to know for complex geometry, therefore they are processed by the finite element analysis which takes long time. In this paper, the response surface is considered to increase efficiency of the reliability analysis for crack growth life of a turbine wheel. The approximation model of the stress intensity factors is obtained by the regression analysis for FEA data and the response surface of crack growth life is generated for selected factors. The reliability analysis is operated by the Monte Carlo Simulation for the response surface. The results indicate that the response surface could reduce computations that need for reliability analysis for the turbine wheel, which is hard to derive stress intensity factor equation, successfully.

Determination of Stress Intensity Factor for the Crack in Anisotropic Solids Using the Finite Element Method (유한요소법에 의한 이방성재료내 균열의 응력확대계수 결정)

  • Lim, W.K.;Jin, Y.K.;Kang, S.J.
    • Proceedings of the KSME Conference
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    • pp.234-239
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    • 2001
  • The stress intensity factors have been widely used in numerical studies of crack growth direction. However in many cases, omissive terms of the series expansion are quantitatively significant, so we consider the computation of such terms. For this purpose, we used the finite element method with isometric quadratic quarter-point elements. For examples, infinite square plate with a slant crack subjected to a uniaxial load is analyzed. The numerical analysis were performed for the wide range of crack tip element lengths and inclined angles. The numerical results obtained are compared with the theoretical solutions. Also they were accurate and efficient.

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Analysis on Correlation between AE Parameters and Stress Intensity Factor using Principal Component Regression and Artificial Neural Network (주성분 회귀분석 및 인공신경망을 이용한 AE변수와 응력확대계수와의 상관관계 해석)

  • Kim, Ki-Bok;Yoon, Dong-Jin;Jeong, Jung-Chae;Park, Phi-Iip;Lee, Seung-Seok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.1
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    • pp.80-90
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    • 2001
  • The aim of this study is to develop the methodology which enables to identify the mechanical properties of element such as stress intensity factor by using the AE parameters. Considering the multivariate and nonlinear properties of AE parameters such as ringdown count, rise time, energy, event duration and peak amplitude from fatigue cracks of machine element the principal component regression(PCR) and artificial neural network(ANN) models for the estimation of stress intensity factor were developed and validated. The AE parameters were found to be very significant to estimate the stress intensity factor. Since the statistical values including correlation coefficients, standard mr of calibration, standard error of prediction and bias were stable, the PCR and ANN models for stress intensity factor were very robust. The performance of ANN model for unknown data of stress intensity factor was better than that of PCR model.

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3-D Analysis of Stress Distribution Around Micro Hole by F.E.M. (유한 요소법에 의한 미소 원공 주위의 응력 분포에 대한 3차원 해석)

  • 송삼홍;김진봉
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.5
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    • pp.1462-1471
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    • 1991
  • 본 연구에서는 미소 결함주위에서 발생, 전파하는 균열들에 미치는 초기 결함 깊이와 상호 간섭 영향을 검토하기 위하여 기존 재료가 갖고 있는 결함이나 비금속 개 재물로 대신할 수 있다고 생각되는 미소 원공의 크기를 변화시킨 모델에 대해 유한 요 소법을 이용하여 3차원적으로 응력을 해석하였다. 실제 사용하고 있는 부재에 결함 들이 존재할 경우 응력장의 간섭으로 피로 균열 진전이 가속화됨으로 미소 원공 주위 의 응력 분포 및 미소 원공사이의 응력장의 간섭과 미소 원공에서 발생, 전파하는 표 면 균열의 응력 확대 계수에 미치는 영향에 대하여 비교검토 하였다.

Determination of stress intensity factors of bent and eccentric cracks by multi-point selection method (다점선정법에 의한 편심 및 굴절균열의 응력확대계수의 결정)

  • 김종주;서인보;최선호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1079-1086
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    • 1990
  • Recently, demand for the experimental analysis of crack, such as arbitrary or distributed ones which has been considered quite difficult to investigate by the theoretical and numerical method, is increasing. Among existent experimental methods applied to the analysis of stress intensity factors, the slab analogy method have the following merits; cracks can be replaced by similarity-shaped rigid body, and the distribution of stress is represented by slab curvature of duly bent specimen. For the accuracy improvement of this method, multi-point selection method was introduced and its accuracy proved by applying this method to the analysis of centrally linear and inclined cracks in a finite plate which are theoretically known. In this paper, moreover, the stress intensity factors of eccentric and skew-symmetric bent cracks were determined by multi-point selection method and newly developed moire tilted master grating method. The results obtained by this method showed good agreement with the reliably theoretical solutions.

Stress Intensity Factor of Single Edge Cracked Plates Considering Materials and Geometry of Patch by p-Convergent Partial Layerwise Model (p-수렴 부분층별모델에 의한 일변균열판의 패치재료 및 기하형상에 따른 응력확대계수)

  • Ahn, Hyeon-Ji;Ahn, Jae-Seok;Woo, Kwang-Sung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.2
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    • pp.191-198
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    • 2010
  • This study investigated that the stress reduction of single edge cracked plates with patch repairs according to different type of patching such as material, size and thickness of patch and adhesive as well as single sided or double sided patches. As a numerical tool, the p-convergent partial layerwise model has been employed. The proposed model is formulated by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacements across thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. Also, total strain energy release rate method is adopted to obtain stress intensity factors. Numerical examples are presented not only to demonstrate the stress reduction effect in terms of non-dimensional stress intensity factor and deflection with respect to different type of patch repairs, but also the accuracy of proposed model.

A Simplified Estimation of Stress Intensity Factor on the Hertzian Contact (혜르츠접촉하에서 응력확대계수의 간단한 계산법)

  • Jin, Song-Bo;Kim, Seock-Sam
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.30-37
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    • 1999
  • 헤르츠 접촉하에 있는 반무한체에서의 표면균열을 살펴보았다. 시편의 응력확대계수 K를 구하기 위해 사용되는 간단화된 방법을 이 논문에 쓰여진 모델에 적용시켰다. 기존에 알려진 결과에 비해 상당히 만족스런 결과를 얻었으며 다른 방법보다 이 방법이 훨씬 더 편리함이 입증되었다.

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Calculation of Stres Intensity Factor in Arbitrarily Shaped Plane Crack by Mobius Transformation (뫼비우스 사상을 이용한 임의의 3차원 평면균열에서의 응력확대계수 계산)

  • An, Deuk-Man
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.4
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    • pp.734-740
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    • 2001
  • In this paper the stress intensity factor under uniform pressure in the arbitrarily-shaped plane crack configuration transformed elliptic crack by Mobius mapping are determined. Using Dysons formula Boussinesq-Papkovich potentials for mode I deformation are constructed. In the example the stress intensity factors are approximately calculated by least square method.

A Study on the Calculation of Stress Intensity Fantors considering Pressure of Crack-Face (균열면의 압력을 고려한 응력확대계수의 결정에 관한 연구)

  • 진치섭;최현태;이홍주
    • Magazine of the Korea Concrete Institute
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    • v.7 no.3
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    • pp.175-186
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    • 1995
  • The determination of the stress intensity factors is investigated by sur-face integral method around the crack tip of the nlass~vc: concrete structure. The surface integral met hod is naturally derived from the standal-ci path integral J. Howevcr. In the J integral method, pressure in the crack-face and body forces can not be considered, while this theory has advantage of ccmsidering many kind of forces, so t.his theory will be useful in investigating more accurate strt:ss states around crack tip. Furthermore. t h~s rrlethod can elerninate unntussary process of using singular elements and fine mesh around crack tip which is used 11; modelling the singularity around crack tip. A computer program for determming $K_I$, $K_{II}$ is tfcvulopcd by applying this theory. $K_I$, $K_{II}$ values usmg X noded isoparametric elements which was proved and variation of the stress intensity factor was investigated by application of darn structures.