Evaluation of Finite-Element Models and Stress-Intensity Factors for Surface Cracks Emanating from Stress Concentrations

2009 ◽  
pp. 34-34-15 ◽  
Author(s):  
PW Tan ◽  
IS Raju ◽  
KN Shivakumar ◽  
JC Newman
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Finite Element Models ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Stress Concentrations

Stress Intensity Factors and Weight Functions for Longitudinal Semi-Elliptical Surface Cracks Inside Thick-Walled Cylinders Using Highly-Refined Finite-Element Models

2010 ◽  
Author(s):  
Adam R. Hinkle ◽  
James E. Holliday ◽  
David P. Jones
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Weight Functions ◽  
Finite Element Models ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Surface Flaws ◽  
Field Singularity

Fracture mechanics and fatigue crack-growth analysis rely heavily upon accurate values of stress intensity factors. They provide a convenient, single-parameter description to characterize the amplitude of the stress-field singularity at the crack tip, and are used to correlate brittle fracture and crack growth in pressure vessel and piping applications. Mode-I stress intensity factors that have been obtained for longitudinal semi-elliptical surface flaws on the inside of thick-walled cylinders using highly-refined finite element models are investigated. Using these results, weight function solutions are constructed and selected geometries are validated.

scholarly journals Stress-Intensity Factors for Internal Surface Cracks in Cylindrical Pressure Vessels

1980 ◽  
Vol 102 (4) ◽  
pp. 342-346 ◽  
Author(s):  
J. C. Newman ◽  
I. S. Raju
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Intensity ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Internal Surface ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Wide Range

The purpose of this paper is to present stress-intensity factors for a wide range of semi-elliptical surface cracks on the inside of pressurized cylinders. The ratio of crack depth to crack length ranged from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 to 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employ singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated from a nodal-force method. An equation for the stress-intensity factors was obtained from the results of the present analysis. The equation applies over a wide range of configuration parameters and was within about 5 percent of the present results. A comparison was also made between the present results and other analyses of internal surface cracks in cylinders. The results from a boundary-integral equation method were in good agreement (± 2 percent) and those from another finite-element method were in fair agreement (± 8 percent) with the present results.

Automated System for Analyzing Stress Intensity Factors of Three-Dimensional Cracks: Its Application to Analyses of Two Dissimilar Semi-Elliptical Surface Cracks in Plate

1997 ◽  
Vol 119 (1) ◽  
pp. 18-26 ◽  
Author(s):  
S. Yoshimura ◽  
J.-S. Lee ◽  
G. Yagawa
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Automated System ◽  
Present System ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Knowledge Processing ◽  
Geometry Model

This paper describes a new automated system for analyzing the stress intensity factors (SIFs) of three-dimensional cracks. A geometry model containing one or several three-dimensional cracks is defined using a commercial CAD system, DESIGNBASE. Several local distributions of node density are chosen from the database of the present system, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay method. A user imposes material properties and boundary conditions onto parts of the geometry model such as loops and edges by clicking them with a mouse and by inputting values. For accurate analyses of the stress intensity factors, finer elements are generated in the vicinity of crack tips, thanks to the fuzzy knowledge processing. The singular elements such that the midpoint nodes near crack front are shifted at the quarter-points are automatically placed along the three-dimensional crack front. The complete finite element model generated is given to a commercial finite element code, MARC, and a stress analysis is performed. The stress intensity factors are calculated using the displacement extrapolation method. To demonstrate practical performances of the present system, two dissimilar semi-elliptical surface cracks in a plate subjected to uniform tension are solved, and their interaction effects are discussed in detail. It is shown from the results that ASME Boiler and Pressure Vessel Code, Section XI, Appendix A gives a conservative stress intensity factor for two identical adjacent surface cracks and for two dissimilar adjacent surface cracks.

Effects of Bonded Crack Retarders on Fatigue Parameters of FSWed Integral Panel

2014 ◽  
Vol 891-892 ◽  
pp. 627-632
Author(s):  
Yu E Ma ◽  
Pan Fu Xu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Damage Tolerance ◽  
Weld Zone ◽  
Finite Element Models ◽  
Cohesive Elements ◽  
Intensity Factors ◽  
Friction Stir

As known, friction stir welded (FSWed) joints are mature to be applied in aircraft structure. However, the weld creates local discontinuity in property and local tensile residual stress, which harm the damage tolerance of welded panels. So crack retarders were bonded in the weld zone to improve damage tolerance. Finite element method was used to calculate stress intensity factors by ABAQUS software. Finite element models were built to simulate the function of bonded retarder. Cohesive elements were used between the substrate panel and bonded retarder. A Fortran program was made to input residual stress to finite element models. Stress intensity factors from residual stress with and without bonded retarders were calculated and compared. Effects of residual stress on stress intensity factors and redistribution of residual stress were taken into considered. Effective R ratios were calculated with crack growing through the weld. Effects of bonded retarder on stress intensity factors were calculated. The results were compared with the experimental findings.

Weight Functions and Stress Intensity Factors for Eccentric through Cracks in a 3-D Rectangular Plate Subjected to In-Plane Loading

2016 ◽  
Vol 853 ◽  
pp. 8-14
Author(s):  
Xu Teng Hu ◽  
Xu Jia ◽  
Ying Dong Song
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Rectangular Plate ◽  
Stress Intensity Factors ◽  
Interpolation Method ◽  
Unknown Coefficient ◽  
Weight Functions ◽  
Finite Element Models ◽  
Intensity Factors ◽  
Aspect Ratios

Three unknown coefficient weight functions for eccentric through cracks in a 3-D rectangular plate subjected to in-plane loading are proposed. 3-D finite element models of cracked rectangular plates within the whole range of crack aspect ratios, i.e., 0≤e/W≤0.8, 0.08≤a/(W-e)≤0.9, were established to obtain a reference SIF database for both crack points A and B, rather than 2-D finite element models. To improve the accuracy of the weight function, the coefficients were derived from this database using the Binary Lagrange Interpolation Method instead of Curve-Fitting Expression. Comparisons of stress intensity factors calculated using the present weight functions with finite element data for the high-order power law and residual stress distributions show high accuracy of the present weight functions.

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