Modelling multiple cohesive crack propagation using a finite element-scaled boundary finite element coupled method
- Authors: Ooi, Ean Tat , Yang, Zhenjun
- Date: 2009
- Type: Text , Journal article
- Relation: Engineering Analysis with Boundary Elements Vol. 33, no. 7 (2009), p. 915-929
- Full Text: false
- Reviewed:
- Description: This paper presents an extension of the recently-developed finite element-scaled boundary finite element (FEM-SBFEM) coupled method to model multiple crack propagation in concrete. The concrete bulk and fracture process zones are modelled using SBFEM and nonlinear cohesive interface finite elements (CIEs), respectively. The CIEs are automatically inserted into the SBFEM mesh as the cracks propagate. The algorithm previously devised for single crack propagation is augmented to model problems with multiple cracks and to allow cracks to initiate in an un-cracked SBFEM mesh. It also addresses crack propagation from one subdomain into another, as a result of partitioning a coarse SBFEM mesh, required for some mixed-mode problems. Each crack in the SBFEM mesh propagates when the sign of the Mode-I stress intensity factor at the crack tip turns positive from negative. Its propagation angle is determined using linear elastic fracture mechanics criteria. Three concrete beams involving multiple crack propagation are modelled. The predicted crack propagation patterns and load-displacement curves are in good agreement with data reported in literature. © 2009 Elsevier Ltd. All rights reserved.
Automatic dynamic crack propagation modeling using polygon scaled boundary finite elements
- Authors: Ooi, Ean Tat , Shi, Mingguang , Song, Chongmin , Tin-Loi, Francis , Yang, Zhenjun
- Date: 2013
- Type: Text , Conference proceedings
- Relation: 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012; Sydney, NSW; Australia; 11th-14th Dec 2012 published in From Materials to Structures: Advancement Through Innovation p. 411-416
- Full Text: false
- Reviewed:
- Description: This study develops a simple and efficient methodology for automatic dynamic crack propagation modeling in structures. It uses high order, arbitrary n-sided polygon elements that are constructed within the scaled boundary finite element framework. Each polygon is treated as a scaled boundary finite element subdomain and their governing equations of equilibrium are assembled using standard finite element procedures. Polygon meshes are automatically generated from a Delaunay triangulated mesh. This method inherits all the positive characteristics of the scaled boundary finite element method. Orders of singularities of any kind can be accurately represented in a unified manner by generalized stress intensity factors to evaluate the crack propagation criterion without dense meshes around the crack tip, special purpose elements or nodal enrichment functions. Crack propagation is efficiently modeled using a simple, yet flexible automatic local remeshing algorithm that is linked to the pre-processing module of a commercial finite element package and can be applied to any polygon mesh. Remeshing involves only polygons around the crack and only minimally changes the global mesh structure. Application of the methodology to model dynamic crack propagation problems is demonstrated by two numerical examples. It is found that the predicted dynamic fracture parameters e.g. dynamic stress intensity factor histories, crack velocity histories, crack length histories and crack paths show good agreement with experiment observations and numerical simulations reported in the literature. © 2013 Taylor & Francis Group.
- Description: From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012
Modelling dynamic crack propagation using the scaled boundary finite element method
- Authors: Ooi, Ean Tat , Yang, Zhenjun
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal for Numerical Methods in Engineering Vol. 88, no. 4 (2011), p. 329-349
- Full Text: false
- Reviewed:
- Description: This study presents a novel application of the scaled boundary finite element method (SBFEM) to model dynamic crack propagation problems. Accurate dynamic stress intensity factors are extracted directly from the semi-analytical solutions of SBFEM. They are then used in the dynamic fracture criteria to determine the crack-tip position, velocity and propagation direction. A simple, yet flexible remeshing algorithm is used to accommodate crack propagation. Three dynamic crack propagation problems that include mode-I and mix-mode fracture are modelled. The results show good agreement with experimental and numerical results available in the literature. It is found that the developed method offers some advantages over conventional FEM in terms of accuracy, efficiency and ease of implementation. © 2011 John Wiley & Sons, Ltd.
Automatic modelling of cohesive crack propagation in concrete using polygon scaled boundary finite elements
- Authors: Ooi, Ean Tat , Song, Chongmin , Tin-Loi, Francis , Yang, Zhenjun
- Date: 2012
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 93, no. (2012), p. 13-33
- Full Text: false
- Reviewed:
- Description: An automatic cohesive crack propagation modelling methodology for quasi-brittle materials using polygon elements is presented. Each polygon is treated as a subdomain that is modelled by the scaled boundary finite element method (SBFEM). Generalised stress intensity factors (SIFs) based on matrix power function solutions of singular stress fields obtained from the SBFEM following standard finite element stress recovery procedures is used to evaluate the crack propagation criterion and determine the crack propagation direction. Interface elements model the fracture process zones and are automatically inserted into the polygon mesh as the crack propagates. A shadow domain procedure couples the polygons and interface elements. It computes the load-displacement response and crack propagation criterion, taking into account the cohesive tractions on the crack edges that are modelled as side-face tractions in the SBFEM. Cracks are propagated using a simple, yet flexible local remeshing procedure that can remesh any arbitrary polygon. Only minimal changes are made to the global mesh structure each time the remeshing algorithm is called. Five cohesive crack propagation benchmarks are modelled to validate the developed method and demonstrate its salient features. © 2012 Elsevier Ltd.
Dynamic crack propagation simulation with scaled boundary polygon elements and automatic remeshing technique
- Authors: Ooi, Ean Tat , Shi, Mingguang , Song, Chongmin , Tin-Loi, Francis , Yang, Zhenjun
- Date: 2013
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 106, no. (2013), p. 1-21
- Full Text: false
- Reviewed:
- Description: An efficient methodology for automatic dynamic crack propagation simulations using polygon elements is developed in this study. The polygon mesh is automatically generated from a Delaunay triangulated mesh. The formulation of an arbitrary n-sided polygon element is based on the scaled boundary finite element method (SBFEM). All kind of singular stress fields can be described by the matrix power function solution of a cracked polygon. Generalised dynamic stress intensity factors are evaluated using standard finite element stress recovery procedures. This technique does not require local mesh refinement around the crack tip, special purpose elements or nodal enrichment functions. An automatic local remeshing algorithm that can be applied to any polygon mesh is developed in this study to accommodate crack propagation. Each remeshing operation involves only a small patch of polygons around the crack tip, resulting in only minimal change to the global mesh structure. The increase of the number of degrees-of-freedom caused by crack propagation is moderate. The method is validated using four dynamic crack propagation benchmarks. The predicted dynamic fracture parameters show good agreement with experiment observations and numerical simulations reported in the literature. © 2013 Elsevier Ltd.
Polygon scaled boundary finite elements for crack propagation modelling
- Authors: Ooi, Ean Tat , Song, Chongmin , Tin-Loi, Francis , Yang, Zhenjun
- Date: 2012
- Type: Text , Journal article
- Relation: International Journal for Numerical Methods in Engineering Vol. 91, no. 3 (2012), p. 319-342
- Full Text: false
- Reviewed:
- Description: An automatic crack propagation modelling technique using polygon elements is presented. A simple algorithm to generate a polygon mesh from a Delaunay triangulated mesh is implemented. The polygon element formulation is constructed from the scaled boundary finite element method (SBFEM), treating each polygon as a SBFEM subdomain and is very efficient in modelling singular stress fields in the vicinity of cracks. Stress intensity factors are computed directly from their definitions without any nodal enrichment functions. An automatic remeshing algorithm capable of handling any n-sided polygon is developed to accommodate crack propagation. The algorithm is simple yet flexible because remeshing involves minimal changes to the global mesh and is limited to only polygons on the crack paths. The efficiency of the polygon SBFEM in computing accurate stress intensity factors is first demonstrated for a problem with a stationary crack. Four crack propagation benchmarks are then modelled to validate the developed technique and demonstrate its salient features. The predicted crack paths show good agreement with experimental observations and numerical simulations reported in the literature. © 2012 John Wiley & Sons, Ltd.
Efficient prediction of deterministic size effects using the scaled boundary finite element method
- Authors: Ooi, Ean Tat , Yang, Zhenjun
- Date: 2010
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 77, no. 6 (2010), p. 985-1000
- Full Text: false
- Reviewed:
- Description: This paper develops an efficient numerical approach to predict deterministic size effects in structures made of quasi-brittle materials using the scaled boundary finite element method (SBFEM). Depending on the structure's size, two different SBFEM-based crack propagation modelling methodologies are used for fracture analyses. When the length of the fracture process zone (FPZ) in a structure is of the order of its characteristic dimension, nonlinear fracture analyses are carried out using the finite element-SBFEM coupled method. In large-sized structures, a linear elastic fracture mechanics (LEFM)-based SBFEM is used to reduce computing time due to small crack propagation length required to represent the FPZ in an equivalent nonlinear analysis. Remeshing is used in both methods to model crack propagation with crack paths unknown a priori. The resulting peak loads are used to establish the size effect laws. Three concrete structures were modelled to validate the approach. The predicted size effect is in good agreement with experimental data. The developed approach was found more efficient than the finite element method, at least in modelling LEFM problems and is thus an attractive tool for predicting size effect. © 2010 Elsevier Ltd.
Dynamic cohesive crack propagation modelling using the scaled boundary finite element method
- Authors: Ooi, Ean Tat , Yang, Zhenjun , Guo, Zaoyang
- Date: 2012
- Type: Text , Journal article
- Relation: Fatigue and Fracture of Engineering Materials and Structures Vol. 35, no. 8 (2012), p. 786-800
- Full Text: false
- Reviewed:
- Description: This study develops a scaled boundary finite element method (SBFEM)-based approach for modelling fast cohesive crack propagation in quasi-brittle materials subjected to transient dynamic loadings. In this approach, the elastic bulk material is modelled by SBFEM subdomains and the cracks by nonlinear cohesive interface finite elements that are automatically inserted by a remeshing procedure. The global equation system is solved using an implicit time integration algorithm. Because all the solutions (displacements, stresses, velocities, accelerations) are semi-analytical in an SBFEM subdomain, this approach offers a few advantages over other methods, such as accurate calculation of dynamic stress intensity factors and T-stress without using fine crack-tip meshes, simpler remeshing, more accurate and efficient mesh mapping, and the need of much fewer degrees of freedom for the same accuracy. The approach is validated by modelling two concrete beams under impact, subjected to mode-I and mixed-mode fracture, respectively. © 2012 Blackwell Publishing Ltd.