scholarly journals Two finite element techniques for computing mode I stress intensity factors in two- or three-dimensional problems

1981 ◽  
Author(s):  
S.K. Iskander
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Mode I ◽  
Intensity Factors

A finite element study of stress fields and stress intensity factors in tubular joints

1995 ◽  
Vol 30 (2) ◽  
pp. 135-142 ◽  
Author(s):  
D Bowness ◽  
M M K Lee
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Stress Intensity Factors ◽  
Numerical Models ◽  
Three Dimensional ◽  
Intensity Factors ◽  
Numerical Work ◽  
Tubular Joints ◽  
Jacket Structures

This paper reports a study on the determination of stress intensity factors in tubular joints in offshore jacket structures. Using finite elements, information on stress concentration factors and through-thickness stress distributions was first obtained from uncracked geometries. This was correlated with the stress intensity factors in joints containing semi-elliptical cracks which were modelled with line-spring elements. The validity of the numerical models was established, using a simple T-joint, by comparing the results with existing experimental data and results from three-dimensional finite element analyses. Various modelling assumptions used in previous numerical work were critically examined. The multi-planar effects in tubular joints were simulated by subjecting the out-of-plane braces to various loadings and restraints. It was found that a relationship exists between the stress concentration factor, the degree of bending and the stress intensity factor for the various loading and restraint cases considered, and that the stress intensity factors in multi-planar tubular joints can be estimated by suitably modifying an existing empirical equation for surface cracks in plain plates.

Three-Dimensional Mode Separation to Obtain Stress Intensity Factors

2006 ◽  
Author(s):  
Pei Gu ◽  
R. J. Asaro
Keyword(s):  
Stress Intensity ◽  
Crack Propagation ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Integral Approach ◽  
Mode I ◽  
Mode Ii ◽  
Intensity Factors ◽  
Mode Iii ◽  
Mode Separation

For mixed-mode loading at a crack tip under small-scale yielding condition, mode I, mode II and mode III stress intensity factors control the crack propagation. This paper discusses three-dimensional mode separation to obtain the three stress intensity factors using the interaction integral approach. The 2D interaction integral approach to obtain mode I and mode II stress intensity factors is derived to 3D arbitrary crack configuration for mode I, mode II and mode III stress intensity factors. The method is implemented in a finite element code using domain integral method and numerical examples show good convergence for the domains around the crack tip. A complete solution for the three stress intensity factors is obtained for a bar with inclined crack face to the cross-section from numerical calculations. The solution for the bar is plotted into curves in terms of a set of non-dimensional parameters for practical engineering purpose. From the solution, mode mixity along the crack front and its implication to the direction of crack propagation is discussed.

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.

scholarly journals Three- Dimensional Simulation of Crack Propagation using Finite Element Method

2019 ◽  
Vol 9 (2) ◽  
pp. 892-897 ◽  
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Crack Path ◽  
Three Dimensional ◽  
Life Time ◽  
Intensity Factors ◽  
Growth Step ◽  
Finite Element Software

The 3D finite element software ANSYS Workbench software has been employed for simulation of engineering geometries which are containing a pre-cracks and holes. The new feature in this software is using the smart crack growth procedure and the mesh smoothing technique which provides an adaptive and smooth mesh around the crack path as well as the higher stresses area. Under the assumption of LEFM, the stress intensity factors was used as a crack growth criterion which provided as indicators of failure compared to the fracture toughness or threshold stress intensity factors (SIFs) in both static and dynamic loading respectively. The stress intensity factors were calculated for every crack growth step and the fatigue life time was predicted according to the number of cycles. The effect of the nominal notch position of the crack was illustrated. Simulations performed with Ansys show an identical crack path on structures that is in line with that of the experimental and numerical results performed by other researchers.

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