| 1. |
- Bremberg, Daniel, et al.
(författare)
-
A numerical procedure for interaction integrals developed for curved cracks of general shape in 3-D
- 2015
-
Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 62, s. 144-157
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents a numerical procedure for the evaluation of interaction energy integrals used to extract mixed-mode stress intensity factors. The interaction energy integral is expressed as a domain integral, and the proposed numerical procedure delivers accurate results for three-dimensional cracks with curved crack fronts and curved crack surfaces for a rather general set of integration domains. It is clearly shown that, when the curvature of the crack surface becomes sufficiently large, special care must be taken in the evaluation of both the volume and the area integrals involved. To improve the accuracy in the evaluation of the former, a composite rule for the Gaussian quadrature scheme is employed. Four benchmark geometries with available analytical solutions are considered. Firstly, mesh design parameters for planar cracks with straight and curved crack fronts are established. Secondly, non-planar cracks with straight and curved crack fronts are employed to examine the accuracy of the numerical procedure.
|
|
| 2. |
- Bremberg, Daniel, et al.
(författare)
-
Automatic 3-D crack propagation calculations : a pure hexahedral element approach versus a combined element approach
- 2009
-
Ingår i: International Journal of Fracture. - : Springer Science and Business Media LLC. - 0376-9429 .- 1573-2673. ; 157:1-2, s. 109-118
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents an evaluation of two different crack prediction approaches based on a comparison of the stress intensity factor distribution for three example problems. A single edge notch specimen and a quarter circular corner crack specimen subjected to shear displacements and a three point bend specimen with a crack inclined to the mid-plane are examined. The stress intensity factors are determined from the singular stress field close to the crack front. Two different fracture criteria are adopted for the calculation of an equivalent stress intensity factor and crack deflection angle. The stress intensity factor distributions for both numerical methods agree well to available reference solutions. Deviations are recorded at crack front locations near the free surface probably due to global contraction effects and the twisting behaviour of the crack front. Crack propagation calculations for the three point bending specimen give results that satisfy intuitive expectations. The outcome of the study encourages further pursuit of a crack propagation tool based on a combination of elements.
|
|
| 3. |
- Bremberg, Daniel, et al.
(författare)
-
Automatic crack-insertion for arbitrary crack growth
- 2008
-
Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 0013-7944 .- 1873-7315. ; 75:3-4, s. 404-416
-
Tidskriftsartikel (refereegranskat)abstract
- A crack-insertion tool for automatic non-planar crack propagation calculations is under development. The final volume mesh of the cracked structure is achieved by a new approach. The cracked structure boundary is modelled as a discretized skin. A tube-like domain enclosing the crack-front is traced and filled with hexahedral elements while the remaining cracked structure is meshed with tetrahedral elements. The two separate meshes are finally connected by linear MPC equations. Results show that the method works very well for curved crack shapes in complex structures.
|
|
| 4. |
- Bremberg, Daniel, et al.
(författare)
-
Automatic mixed-mode crack propagation based on a combined hexahedral-tetrahedral approach
- 2007
-
Ingår i: Advances in Fracture and Damage Mechanics VI. ; , s. 581-584
-
Konferensbidrag (refereegranskat)abstract
- In the present paper, a new method for inserting cracks with out-of-plane features is presented. Starting point is an arbitrary reference structure and a crack of any shape. The final cracked structure is represented by hexahedral elements in the crack-front region and tetrahedral elements in the remaining structure domain. The tetrahedron is employed to take advantage of the versatile meshing capabilities and the collapsed quarter-point hexahedron gives good crack-tip behaviour. Stress intensity factors are calculated from the asymptotic stress field, retrieved from the integration points near the crack-tip.
|
|
| 5. |
|
|
| 6. |
- Bremberg, Daniel, et al.
(författare)
-
NUMERICAL 3-D FATIGUE CRACK GROWTH ANALYSES OF REAL-LIFE COMPONENTS
- 2010
-
Ingår i: PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE 2010, VOL 1. - NEW YORK : ASME. - 9780791849200 ; , s. 451-458
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a numerical concept far fatigue crack propagation computations, within the theory of the finite element method and the theory of linear elastic fracture mechanics, capable of automatic analysis of curved 3-D crack fronts and non-planar crack surfaces. The general modelling of fatigue crack growth and the present algorithm based on a remeshing technique are described. A comparison to existing analytical solutions for an embedded elliptical crack shows satisfying agreement and a fatigue crack growth analysis of a real-life component illustrates the framework applicability.
|
|
| 7. |
- Dhondt, G., et al.
(författare)
-
Automatic cyclic crack propagation calculations in aircraft engines
- 2010
-
Ingår i: Advances in Fracture and Damage Mechanics VIII. - : Trans Tech Publications Inc.. ; , s. 733-736
-
Konferensbidrag (refereegranskat)abstract
- This document describes a mixed-element approach to perform mixed-mode crack propagation calculations in an arbitrary structure in a fully automatic way. In a preprocessing step a cylindrical volume about the crack front is meshed with hexahedral elements while the remaining parts of the structure at interest are filled with tetrahedrons. Subsequently, a finite element calculation is performed yielding the stress field at the crack tip. The postprocessor determines the stress intensity factors and the 3-dimensional crack growth, leading to a new crack front. This procedure is repeated until a user-defined criterion is reached. The method is illustrated by an aircraft casing component.
|
|
| 8. |
- Dhondt, G., et al.
(författare)
-
Propagation of cracks in selected specimens subject to mixed-mode
- 2010
-
Ingår i: Structural Durability and Health Monitoring. - 1930-2983. ; 6:3-4, s. 305-327
-
Tidskriftsartikel (refereegranskat)abstract
- In a previous article the K-distritubion along the crack front of several mixed-mode specimens was investigated [Dhondt, Chergui, and Buchholz (2001)]. Both the modified virtual crack closure integral method and the quarter point element stress field method yielded results close to the available reference solutions in the literature [Murakami (1987)]. The present paper extends these results in two aspects. First, the meshing procedure used to obtain a focused mesh at the crack front is modified in order to deal with highly curved cracks. Secondly, the K-distribution along the initial crack is used to perform a crack propagation calculation. The form of the propagated cracks agrees well with what one expects and with experimental evidence.
|
|
