The Numerical Analysis and Experimental Study of the Stress Intensity Factor and Outer Surface Strain of the Pressure Pipe with Internal Longitudinal-Cracks

2016 ◽  
Vol 853 ◽  
pp. 221-225
Author(s):  
Jia Sheng He ◽  
Meng Qi Yan ◽  
Xiao Ming Zhu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Outer Surface ◽  
Crack Size ◽  
Surface Strain ◽  
Strain Variation ◽  
Pressure Pipe ◽  
Longitudinal Cracks ◽  
Relationship Of

The strain characteristics in the outer surface of the pipe and the stress intensity factor in crack front with internal longitudinal-cracks were analyzed by the finite element method. According to the results of analysis, the outer surface strain variation to crack size was got and the relationship of stress intensity factor and crack size was known. Based on resistance strain gauges and fiber optic sensing technology, pressure pipe crack extension monitoring device was designed and the outer surface circumferential strain were tested .The results of finite element analysis and experiment are in good agreement. The outer surface strain variation in this paper can be used to analyze the situation of internal longitudinal-cracks extension.That relationship of stress intensity factor and crack size has an important reference to the safety assessment of pipe with internal longitudinal-crack.

Stress Intensity Factor Coefficients for Circumferential ID Surface Flaws in Cylinders for Appendix A of ASME Section XI

2013 ◽  
Author(s):  
Russell C. Cipolla ◽  
Darrell R. Lee
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Flat Plate ◽  
Closed Form ◽  
Fourth Order ◽  
Surface Crack ◽  
Crack Size ◽  
Plate Geometry

The stress intensity factor (KI) equations for a surface crack in ASME Section XI, Appendix A are based on non-dimensional coefficients (Gi) that allow for the calculation of stress intensity factors for a cubic varying stress field. Currently, the coefficients are in tabular format for the case of a surface crack in a flat plate geometry. The tabular form makes the computation of KI tedious when determination of KI for various crack sizes is required and a flat plate geometry is conservative when applied to a cylindrical geometry. In this paper, closed-form equations are developed based on tabular data from API 579 (2007 Edition) [1] for circumferential cracks on the ID surface of cylinders. The equations presented, represent a complete set of Ri/t, a/t, and a/l ratios and include those presented in the 2012 PVP paper [8]. The closed-form equations provide G0 and G1 coefficients while G2 through G4 are obtained using a weight function representation for the KI solutions for a surface crack. These equations permit the calculation of the Gi coefficients without the need to perform tabular interpolation. The equations are complete up to a fourth order polynomial representation of applied stress, so that the procedures in Appendix A have been expanded. The fourth-order representation for stress will allow for more accurate fitting of highly non-linear stress distributions, such as those depicting high thermal gradients and weld residual stress fields. The equations developed in this paper will be added to the Appendix A procedures in the next major revision to ASME Section XI. With the inclusion of equations to represent Gi, the procedures of Appendix A for the determination of KI can be performed more efficiently without the conservatism of using flat plate solutions. This is especially useful when performing flaw growth evaluations where repetitive calculations are required in the computations of crack size versus time. The equations are relatively simple in format so that the KI computations can be performed by either spreadsheet analysis or by simple computer programming. The format of the equations is generic in that KI solutions for other geometries can be added to Appendix A relatively easily.

A Surrogate Model for Predicting Stress Intensity Factor: An Application to Oil and Gas Industry

2017 ◽  
Author(s):  
Arvind Keprate ◽  
R. M. Chandima Ratnayake ◽  
Shankar Sankararaman
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Oil And Gas ◽  
Gaussian Process Regression ◽  
Complex Loading ◽  
Oil And Gas Industry ◽  
Crack Size ◽  
Data Points ◽  
Time Required

Evaluation of the stress intensity factor (SIF) for a crack propagating in a structural component is the analytical basis of linear elastic fracture mechanics (LEFM) approach. Handbook solutions give accurate SIF results for simple crack geometries. For intricate crack geometries and complex loading conditions finite element method (FEM), is used to predict SIF. The main drawback of FEM techniques is that they are prohibitively expensive in terms of computing cost and also very time consuming. In this manuscript, authors have presented a Gaussian Process Regression Model (GPRM), which may be used as an alternative to FEM for predicting SIF of a propagating crack. The GPRM is firstly trained using 70 SIF values obtained by FEM, and then validated by comparing the values of SIF predicted by GPRM and FEM for 30 data points (i.e. combination of crack size and loading). On comparing the aforementioned values the average residual percentage between the two is 2.57%, indicating good agreement between GPRM and FEM model. Also, the time required to predict SIF of 30 data points is reduced from 30 mins (for FEM) to 10 seconds with the help of proposed GPRM.

Closed Form Solutions for Stress Intensity Factor Coefficients for Circumferential ID Surface Flaws in Cylinders in ASME Section XI Appendix A

2012 ◽  
Author(s):  
Russell C. Cipolla ◽  
Darrell R. Lee
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Flat Plate ◽  
Closed Form ◽  
Fourth Order ◽  
Surface Crack ◽  
Crack Size ◽  
Plate Geometry

The stress intensity factor (KI) equations for a surface crack in ASME Section XI, Appendix A are based on non-dimensional coefficients (Gi) that allow for the calculation of stress intensity factors for a cubic varying stress field. Currently, the coefficients are in tabular format for the case of a surface crack in a flat plate geometry. The tabular form makes the computation of KI tedious when determination of KI for various crack sizes is pursued and a flat plate geometry is conservative when applied to a cylindrical geometry. In this paper, closed-form equations are developed based on tabular data from API 579 (2007 Edition) [1] for circumferential cracks on the ID surface of cylinders. The closed-form equations provide G0 and G1 coefficients while G2 through G4 are obtained using a weight function representation for the KI solutions for a surface crack. These equations permit the calculation of the Gi coefficients without the need to perform tabular interpolation. The equations are complete up to a fourth order polynomial representation of applied stress, so that the procedures in Appendix A have been expanded. The fourth-order representation for stress will allow for more accurate fitting of highly non-linear stress distributions, such as those depicting high thermal gradients and weld residual stress fields. It is expected that the equations developed in this paper will be added to the Appendix A procedures. With the inclusion of equations to represent Gi, the procedures of Appendix A for the determination of KI can be performed more efficiently without the conservatism of using flat plate solutions. This is especially useful in performing flaw growth calculations where repetitive calculations are required in the computations of crack size versus time. The equations are relatively simple in format so that the KI computations can be performed by either spreadsheet analysis or by simple computer programming. The format of the equations is generic in that KI solutions for other geometries can be added to Appendix A relatively easily.

Technical Basis for Equations for Stress Intensity Factor Coefficients in ASME Section XI Appendix A

2004 ◽  
Author(s):  
Russell C. Cipolla ◽  
Darrell R. Lee
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Programming Languages ◽  
Fourth Order ◽  
Surface Crack ◽  
Crack Size ◽  
Graphical Form

The stress intensity factor (KI) equations in ASME Section XI, Appendix A are based on non-dimensional coefficients (Gi) that allow for the calculation of stress intensity factors for a cubic varying stress field for a surface crack, and linear varying stress field for a sub-surface crack. Currently, the coefficients are in tabular format for the case of a surface crack in a flat plate geometry. For the buried elliptical flaw, the Gi coefficients are in graphical format. The tabular/graphical form makes the computation of KI tedious when determination of KI for various crack sizes is pursued. In this paper, closed-form equations are developed based on a weight function representation for the KI solutions for a surface crack. These equations permit the calculation of the Gi coefficients without the need to perform tabular interpolation within the current tables in Article 3320 of Appendix A. The equations are complete up to a fourth order polynomial representation of applied stress, so that the procedures in Appendix A have been expanded. The fourth-order representation for stress will allow for more accurate fitting of highly non-linear stress distributions, such as those depicting high thermal gradients and weld residual stress fields. It is expected that the equations developed in this paper will be added to the Appendix A procedures. With the inclusion of equations to represent Gi, the procedures of Appendix A for the determination of KI can be performed more efficiently. This is especially useful in performing flaw growth calculations where repetitive calculations are required in the computations of crack size versus time. The equations are relatively simple in format so that the KI computations can be performed by either spreadsheet analysis or by simple computer programming languages. The format of the equations is generic in that KI solutions for other geometries can be added to Appendix A relatively easily.

Bounding Residual Stress Intensity Factor Profiles for Fracture Assessment of Pipe Girth Welds

2015 ◽  
Author(s):  
P. John Bouchard ◽  
Jino Mathew
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Size ◽  
Contour Method ◽  
Stress Measurements ◽  
Axial Residual Stress ◽  
Fracture Assessment ◽  
Girth Welds

The effect of residual stress on potential crack growth and fracture in welded structures is usually assessed through its contribution to the stress intensity factor (SIF) for the crack size and shape of interest. The idea of defining bounding residual SIF profiles for surface breaking circumferential cracks in pipe butt welds was presented at ASME PVP2013. The limiting profiles were based on through-thickness residual stress measurements for eight pipe girth welds. This paper presents new axial residual stress measurements made using the contour method for an Esshete 1250 stainless steel pipe girth weld. A wide variation in the through-wall distribution of axial residual stress around the circumference of the pipe is observed which has a significant effect on calculated values of SIF for postulated surface breaking circumferential cracks. Nonetheless, SIFs based on all of the new measurements (a total of 14 profiles) are comfortably bounded by the simple SIF prescriptions previously published.

Stress Intensity Factor Handbook: Comparison of RSEM and ASME XI Codes

2015 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Mechanic ◽  
Crack Size ◽  
Weight Functions ◽  
Thickness Variation ◽  
Element Analysis ◽  
Critical Crack ◽  
Practical Applications

For fracture mechanic applications at design level or during operation the basic parameter used is the elastic stress intensity factor K. This stress intensity factor can be evaluated through different methods: formulas, influence or weight functions or direct elastic finite element analysis of the cracked structure. After a brief review of available methods to develop elastic analysis of the fracture mechanic parameter K (stress intensity factor), this paper will compare French RSE-M Appendix 5 handbook and corresponding ASME-XI draft Appendix A-3000 handbook under development for cylindrical cracked structures (pipes or vessels) in a first step. In a future step, other structures (elbows, thickness variation…) and other crack types or locations will be considered. The cross reference validations and the technical white papers will be discussed in the paper. A short overview of plasticity corrections proposed by these 2 different Codes will be presented, compared and discussed in accordance with the validation analysis available. Finally, some differences between these 2 handbooks can have important safety consequences in their practical applications, some over-conservatism have to be better understand and will be discussed in term of consequences on different practical applications, like fatigue or corrosion crack growth, or critical crack size in brittle or ductile regime of nuclear components.

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