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Douglas A. Scarth - One of the best experts on this subject based on the ideXlab platform.

  • Weight Function Method With Segment-Wise Polynomial Interpolation to Calculate Stress Intensity Factors for Complicated Stress Distributions
    Journal of Pressure Vessel Technology, 2014
    Co-Authors: Kunio Hasegawa, Douglas A. Scarth
    Abstract:

    Many solutions of the stress intensity factor have been proposed in recent years. However, most of them take only third or fourth-order polynomial stress distributions into account. For complicated stress distributions which are difficult to be represented as third or fourth-order polynomial equations over the stress distribution area such as residual stress distributions or thermal stress distributions in dissimilar materials, it is important to further improve the accuracy of the stress intensity factor. In this study, a Weight Function Method with segment-wise polynomial interpolation is proposed to calculate solutions of the stress intensity factor for complicated stress distributions. By using this Method, solutions of the stress intensity factor can be obtained without employing finite element analysis or difficult calculations. It is therefore easy to use in engineering applications. In this Method, the stress distribution area is firstly divided into several segments and the stress distribution in each segment is curve fitted to segment-wise polynomial equation. The stress intensity factor is then calculated based on the Weight Function Method and the fitted stress distribution in each segment. Some example solutions for both infinite length cracks and semi-elliptical cracks are compared with the results from finite element analysis. In conclusion, it is confirmed that this Method is applicable with high accuracy to the calculation of the stress intensity factor taking actual complicated stress distributions into consideration.

  • Technical Basis for Application of Weight Function Method for Calculation of Stress Intensity Factor for Surface Flaws Proposed for ASME Section XI Appendix A
    Journal of Pressure Vessel Technology, 2013
    Co-Authors: Douglas A. Scarth, Russell C. Cipolla
    Abstract:

    Analytical evaluation procedures for determining the acceptability of flaws detected during in-service inspection of nuclear power plant components are provided in Section XI of the ASME Boiler and Pressure Vessel Code. Linear elastic fracture mechanics based evaluation procedures in ASME Section XI require calculation of the stress intensity factor. A Method for calculating the stress intensity factor is provided in Appendix A of ASME Section XI. This Method consists of a two-step process. In the first step, the stress distribution, as calculated in the absence of the flaw, is obtained at the flaw location. For a surface flaw, the stress distribution at the flaw location is then fitted to a third-order polynomial equation. In the second step, the fitted polynomial representation of the stress distribution is used with standardized influence coefficients to calculate the stress intensity factor. An alternate Method for calculation of the stress intensity factor for a surface flaw that makes explicit use of the universal Weight Function Method and does not require a polynomial fit to the actual stress distribution is proposed in this paper for implementation into Appendix A of ASME Section XI. Universal Weight Function coefficients are determined from standardized influence coefficients through closed-form equations. Closed-form equations for calculation of the stress intensity factor are provided. The technical basis and verification for this alternate Method for calculation of the stress intensity factor are described in this paper.

  • Weight Function Method With Segment-Wise Polynomial Interpolation to Calculate Stress Intensity Factors for Complicated Stress Distributions
    Volume 1: Codes and Standards, 2012
    Co-Authors: Hiroto Itoh, Kunio Hasegawa, Douglas A. Scarth
    Abstract:

    Many solutions of the stress intensity factor have been proposed in recent years. However, most of them take only third or fourth-order polynomial stress distributions into account. For complicated stress distributions which are difficult to be represented as third or fourth-order polynomial equations over the stress distribution area such as residual stress distributions or thermal stress distributions in dissimilar materials, it is important to further improve the accuracy of the stress intensity factor.In this study, a Weight Function Method with segment-wise polynomial interpolation is proposed to calculate solutions of the stress intensity factor for complicated stress distributions. By using this Method, solutions of the stress intensity factor can be obtained without employing finite element analysis or difficult calculations. It is therefore easy to use in engineering applications. In this Method, the stress distribution area is firstly divided into several segments and the stress distribution in each segment is curve fitted to segment-wise polynomial equation. The stress intensity factor is then calculated based on the Weight Function Method and the fitted stress distribution in each segment. Some example solutions for both infinite length cracks and semi-elliptical cracks are compared with the results from finite element analysis. In conclusion, it is confirmed that this Method is applicable with high accuracy to the calculation of the stress intensity factor taking actual complicated stress distributions into consideration.Copyright © 2012 by ASME

  • Technical Basis for Proposed Weight Function Method for Calculation of Stress Intensity Factor for Surface Flaws in ASME Section XI Appendix A
    Volume 1: Codes and Standards, 2011
    Co-Authors: Douglas A. Scarth, Russell C. Cipolla
    Abstract:

    Analytical evaluation procedures for determining the acceptability of flaws detected during in-service inspection of nuclear power plant components are provided in Section XI of the ASME Boiler and Pressure Vessel Code. Linear elastic fracture mechanics based evaluation procedures in ASME Section XI require calculation of the stress intensity factor. A Method for calculating the stress intensity factor is provided in Appendix A of ASME Section XI. This Method consists of a two-step process. In the first step, the stress distribution, as calculated in the absence of the flaw, is obtained at the flaw location. For a surface flaw, the stress distribution at the flaw location is then fitted to a third-order polynomial equation. In the second step, the fitted polynomial representation of the stress distribution is used with standardized influence coefficients to calculate the stress intensity factor. An alternate Method for calculation of the stress intensity factor for a surface flaw that makes explicit use of the Universal Weight Function Method and does not require a polynomial fit to the actual stress distribution is proposed in this paper for implementation into Appendix A of ASME Section XI. Universal Weight Function coefficients are determined from standardized influence coefficients through closed-form equations. Closed-form equations for calculation of the stress intensity factor are provided. The technical basis and verification for this alternate Method for calculation of the stress intensity factor are described in this paper.Copyright © 2011 by ASME

  • universal Weight Function consistent Method to fit polynomial stress distribution for calculation of stress intensity factor
    ASME 2010 Pressure Vessels and Piping Division K-PVP Conference, 2010
    Co-Authors: Douglas A. Scarth
    Abstract:

    Procedures for analytical evaluation of flaws in nuclear pressure boundary components are provided in Section XI of the ASME B&PV Code. The flaw evaluation procedure requires calculation of the stress intensity factor. Engineering procedures to calculate the stress intensity factor are typically based on a polynomial equation to represent the stress distribution through the wall thickness, where the polynomial equation is fitted using the least squares Method to discrete data point of stress through the wall thickness. However, the resultant polynomial equation is not always an optimum fit to stress distributions with large gradients or discontinuities. Application of the Weight Function Method enables a more accurate representation of the stress distribution for the calculation of the stress intensity factor. Since engineering procedures and engineering software for flaw evaluation are typically based on the polynomial equation to represent the stress distribution, it would be desirable to incorporate the advantages of the Weight Function Method while still retaining the framework of the polynomial equation to represent the stress distribution when calculating the stress intensity factor. A Method to calculate the stress intensity factor using a polynomial equation to represent the stress distribution through the wall thickness, but which provides the same value of the stress intensity factor as is obtained using the Universal Weight Function Method, is provided in this paper.Copyright © 2010 by ASME

Rahmatollah Ghajar - One of the best experts on this subject based on the ideXlab platform.

  • Crack growth pattern prediction in a thin walled cylinder based on closed form thermo-elastic stress intensity factors
    Journal of Mechanical Science and Technology, 2017
    Co-Authors: Mohammad Abbaspour Niasani, Rahmatollah Ghajar, Hamed Saeidi Googarchin, Seyed Mohammad Hossein Sharifi
    Abstract:

    Circumferential crack growth pattern in a thin-walled cylinder is studied. Thermo-elastic stresses in a cylinder subjected to thermomechanical loads are extracted. Closed form thermo-elastic stress intensity factor for cracked cylinder are derived using Weight Function Method. An algorithm is developed to simulate different crack growth patterns utilizing a very high efficiency Weight Function Method. This would lessen the taken time for the analyses compared to other numerical Methods such as FEM. Results show that while the load effect on cylinder subjected to thermal load lead to the crack growth in small aspect ratio, in cylinder subjected to mechanical loads, it would lead to the growth of crack in large aspect ratio. The results show that, apart from load effects, the cylinders containing initial semi-circular crack have the longest life among the cylinders containing initial semi-elliptical crack with the same initial depth.

  • analysis of thermal stress intensity factors for cracked cylinders using Weight Function Method
    International Journal of Engineering Science, 2010
    Co-Authors: S M Nabavi, Rahmatollah Ghajar
    Abstract:

    In this paper a general Weight Function was derived to evaluate the thermal stress intensity factors of a circumferential crack in cylinders. The Weight Function derived is valid for a wide range of thin- to thick-walled cylinders and relative crack depth. Closed-form stress intensity factor based on the Weight Function Method was derived as a Function of the Biot number and relative depth and various inner-to-outer radius ratios of cylinders. The accuracy of the analysis has been examined using the finite element Method results and were compared to existing solutions for uniform loading in the literature for special geometries, indicating an excellent agreement.

Andrea Spagnoli - One of the best experts on this subject based on the ideXlab platform.

  • expected principal stress directions under multiaxial random loading part i theoretical aspects of the Weight Function Method
    International Journal of Fatigue, 1999
    Co-Authors: Andrea Carpinteri, Ewald Macha, Roberto Brighenti, Andrea Spagnoli
    Abstract:

    As has been observed experimentally by many authors, the position of the fatigue fracture plane appears to strongly depend on the directions of the principal stresses or strains. In Part I of the present work the expected principal stress directions under multiaxial random loading are theoretically obtained by averaging the instantaneous values of the three Euler angles through some suitable Weight Functions which are assumed to take into account the main factors influencing fatigue behaviour. Then, in Part II, it is examined how such theoretical principal directions determined by applying the proposed procedure are correlated to the position of the experimental fracture plane for some fatigue tests reported in the literature.

  • expected principal stress directions under multiaxial random loading part ii numerical simulation and experimental assessment through the Weight Function Method
    International Journal of Fatigue, 1999
    Co-Authors: Andrea Carpinteri, Ewald Macha, Roberto Brighenti, Andrea Spagnoli
    Abstract:

    In Part I of the present work, the theoretical aspects of a proposed procedure to determine the expected principal stress directions under multiaxial random loading have been discussed. This procedure consists of averaging the instantaneous values of the three Euler angles through Weight Functions. In Part II here, a numerical simulation is presented to illustrate the above theoretical Method. As an example, the algorithm proposed is applied to some experimental biaxial in- and out-of-phase stress states to assess the correlation between the expected principal stress directions and the position of the experimental fatigue fracture plane for such tests.

S M Nabavi - One of the best experts on this subject based on the ideXlab platform.

  • analysis of thermal stress intensity factors for cracked cylinders using Weight Function Method
    International Journal of Engineering Science, 2010
    Co-Authors: S M Nabavi, Rahmatollah Ghajar
    Abstract:

    In this paper a general Weight Function was derived to evaluate the thermal stress intensity factors of a circumferential crack in cylinders. The Weight Function derived is valid for a wide range of thin- to thick-walled cylinders and relative crack depth. Closed-form stress intensity factor based on the Weight Function Method was derived as a Function of the Biot number and relative depth and various inner-to-outer radius ratios of cylinders. The accuracy of the analysis has been examined using the finite element Method results and were compared to existing solutions for uniform loading in the literature for special geometries, indicating an excellent agreement.

D. H. Tong - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of various analytical Weight Function Methods base on exact K -solutions of an edge-cracked circular disc
    Engineering Fracture Mechanics, 2018
    Co-Authors: D. H. Tong
    Abstract:

    Abstract Weight Function Method is a powerful tool for the determination of key parameters such as stress intensity factors and crack opening displacements for cracks in complicated stress fields. Accurate determination of the Weight Functions is of primary importance for successful applications of the Method. This paper makes detailed accuracy evaluation of two kinds of widely used approximate (2D) Weight Function approaches, one being based on crack opening displacement for one reference stress, the other on two reference stresses coupled with a geometric condition. To eliminate possible sources of error, the edge-cracked circular disc with exact K-solutions is used for deriving the two kinds of Weight Functions and for benchmarking against the two Weight Function approaches. A highly accurate numerical Weight Function Method using the complex Taylor series expansion and complex finite element computation is also used for assessing the related Green’s Functions. Results from the evaluation will be instructive for accurate determination of Weight Functions for other finite edge-crack geometries.

  • stress intensity factors for surface cracks in single edge notch bend specimen by a three dimensional Weight Function Method
    Fatigue & Fracture of Engineering Materials & Structures, 2016
    Co-Authors: X. C. Zhao, James C. Newman, D. H. Tong
    Abstract:

    A three-dimensional (3D) Weight Function Method is employed to calculate stress intensity factors of quarter-elliptical corner cracks at a semi-circular notch in the newly developed single-edge notch bend specimen. Corner cracks covering a wide range of geometrical parameters under pin-loading and remote tension conditions are analysed. Stress intensity factors from the 3D Weight Function analysis agree well with ABAQUS-Franc3D finite element results. An engineering similitude approach previously developed for the half-elliptical surface crack in single-edge notch bend specimen is also applied to the present corner crack configuration. The results compare well with those from the present Weight Function analysis.

  • Stress intensity factors for surface cracks in single‐edge notch bend specimen by a three‐dimensional Weight Function Method
    Fatigue & Fracture of Engineering Materials & Structures, 2016
    Co-Authors: X. C. Zhao, James C. Newman, D. H. Tong
    Abstract:

    A three-dimensional (3D) Weight Function Method is employed to calculate stress intensity factors of quarter-elliptical corner cracks at a semi-circular notch in the newly developed single-edge notch bend specimen. Corner cracks covering a wide range of geometrical parameters under pin-loading and remote tension conditions are analysed. Stress intensity factors from the 3D Weight Function analysis agree well with ABAQUS-Franc3D finite element results. An engineering similitude approach previously developed for the half-elliptical surface crack in single-edge notch bend specimen is also applied to the present corner crack configuration. The results compare well with those from the present Weight Function analysis.

  • Determination of crack surface displacements for cracks emanating from a circular hole using Weight Function Method
    Fatigue & Fracture of Engineering Materials & Structures, 2012
    Co-Authors: D. H. Tong
    Abstract:

    Cracks emanating from a circular hole are of significant engineering importance, especially in aerospace industry. Accurate determination of key fracture mechanics parameters is essential for damage tolerance design and fatigue life predictions. The purpose of this paper is to provide an efficient and accurate closed-form Weight Function approach to the calculation of crack surface displacements for radial crack(s) emanating from a circular hole in an infinite and finite-width plate. Results were presented for two loading conditions: remote applied stress and uniform stress segment applied to crack surfaces, and extensively compared to recent studies using other Methods in the literature. Both single and double radial cracks were considered, and also the effect of finite plate width on crack surface displacements has been investigated. A brief assessment was made on an engineering estimation of displacements based on a correction of stress intensity factor ratio. It has been demonstrated that the Wu-Carlsson closed-form Weight Functions are very efficient, accurate and easy-to-use for calculating crack surface displacements for arbitrary load conditions. The Method will facilitate fatigue crack closure and other fracture mechanics analyses where accurate crack surface displacements are required.