A mesoscale modelling approach coupling SBFEM, continuous damage phase-field model and discrete cohesive crack model for concrete fracture
- Authors: Yu, Kelai , Yang, Zhenjun , Li, Hui , Ooi, Ean Tat , Li, Shangming , Liu, GuoHua
- Date: 2023
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 278, no. (2023), p.
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- Description: This study develops an innovative numerical approach for simulating complex mesoscale fracture in concrete. In this approach, the concrete meso-structures are generated using a random aggregate generation and packing algorithm. Each aggregate is modelled by a single scaled boundary finite element method (SBFEM) based polygon with the boundary discretized only. The damage and fracture in the mortar is simulated by the continuous damage phase-field regularized cohesive zone model (PF-CZM), and the aggregate-mortar interfaces are modelled by zero-thickness cohesive interface elements (CIEs) with nonlinear softening separation-traction laws. This new approach thus takes full advantages of different methods, including the semi-analytical accuracy and high flexibility in mesh generation and transition of SBFEM, the mesh and length-scale independence of PF-CZM, and the ease-of-use of CIEs in modelling discrete interfacial fracture. These advantages are demonstrated by successful simulations of a few 2D and 3D benchmark examples in mode-I and mixed-mode fracture. © 2022 Elsevier Ltd
Adaptive phase-field modelling of fracture propagation in poroelastic media using the scaled boundary finite element method
- Authors: Wijesinghe, Dakshith , Natarajan, Sundararajan , You, Greg , Khandelwal, Manoj , Dyson, Ashley , Song, Chongmin , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 411, no. (2023), p.
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- Description: A scaled boundary finite element-based phase field formulation is proposed to model two-dimensional fracture in saturated poroelastic media. The mechanical response of the poroelastic media is simulated following Biot's theory, and the fracture surface evolution is modelled according to the phase field formulation. To avoid the application of fine uniform meshes that are constrained by the element size requirement when adopting phase field models, an adaptive refinement strategy based on quadtree meshes is adopted. The unique advantage of the scaled boundary finite element method is conducive to the application of quadtree adaptivity, as it can be directly formulated on quadtree meshes without the need for any special treatment of hanging nodes. Efficient computation is achieved by exploiting the unique patterns of the quadtree cells. An appropriate scaling is applied to the relevant matrices and vectors according the physical size of the cells in the mesh during the simulations. This avoids repetitive calculations of cells with the same configurations. The proposed model is validated using a benchmark with a known analytical solution. Numerical examples of hydraulic fractures driven by the injected fluid in cracks are modelled to illustrate the capabilities of the proposed model in handling crack propagation problems involving complex geometries. © 2023 The Author(s)
Construction of generalized shape functions over arbitrary polytopes based on scaled boundary finite element method's solution of Poisson's equation
- Authors: Xiao, B. , Natarajan, Sundararajan , Birk, Carolin , Ooi, Ean Hin , Song, Chongmin , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal for Numerical Methods in Engineering Vol. 124, no. 17 (2023), p. 3603-3636
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- Description: A general technique to develop arbitrary-sided polygonal elements based on the scaled boundary finite element method is presented. Shape functions are derived from the solution of the Poisson's equation in contrast to the well-known Laplace shape functions that are only linearly complete. The application of the Poisson shape functions can be complete up to any specific order. The shape functions retain the advantage of the scaled boundary finite element method allowing direct formulation on polygons with arbitrary number of sides and quadtree meshes. The resulting formulation is similar to the finite element method where each field variable is interpolated by the same set of shape functions in parametric space and differs only in the integration of the stiffness and mass matrices. Well-established finite element procedures can be applied with the developed shape functions, to solve a variety of engineering problems including, for example, coupled field problems, phase field fracture, and addressing volumetric locking in the near-incompressibility limit by adopting a mixed formulation. Application of the formulation is demonstrated in several engineering problems. Optimal convergence rates are observed. © 2023 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.
Development of scaled boundary finite element method for geotechnical and mining engineering
- Authors: Wijesinghe, Dakshith
- Date: 2023
- Type: Text , Thesis , PhD
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- Description: Numerical methods are a mature field of research and have become an increasingly important tool in mining and geotechnical engineering design practices. Although the advantages of numerical methods in aiding the analysis and solving practical engineering problems have been widely accepted and recognised, there is still a gap for further improvements. One such area is the challenge to consider the complexities of geology and the lack of stratigraphic information in the numerical model. Failure to include geological complexities may lead to overestimating the analysis parameters, such as the safety factor. These difficulties mainly manifest in the form of complex mesh generation due to the need to integrate spatial variable material parameters, capturing complex geological features, requirement of additional meshing algorithms, high human involvement, and long processing time. The scaled boundary finite element method (SBFEM) is a semi-analytical method that has potential to address these types of problems. This thesis focuses on developing the SBFEM to address these challenges so that complex geotechnical and mining engineering can be better modelled. Optimisation problems in geotechnical and mining engineering are also considered by developing a combined SBFEM-genetic algorithm framework for the design and rehabilitation of slopes. To begin with, an image-based mesh generation procedure is developed to automatically integrate the spatially variable material parameters into a computational mesh. The procedure allows the input of large data sets of geological and geometrical information in image format, and the mapping procedure enables the concatenation of any number of material parameters into a single computational mesh. The scaled boundary finite element formulation is used to discretise the governing equations of elasto-plasticity considering a Mohr-Coulomb failure criterion, which is common in soils. A shear strength reduction technique is implemented to analyse the stability of slopes in the form of an output Factor of Safety. The developed method is shown to allow routine changes in the operation of the slopes to consider geometric changes, such as backfilling, excavation and updates to geological sublets, by simply editing the digital image inputs. To extend the SBFEM to more complex geotechnical and mining engineering applications, a formulation that considers the coupled effect of pore pressure and nonlinear deformation of the soil is developed. The image-based mesh generation procedure is incorporated to integrate the geological complexities, which include heterogeneity of strate and phreatic surfaces. The developed technique is applied to study complex case studies of a tailings dam embankment construction and a coal slope rehabilitation project with a construction period. The research also considers geometric optimisation problems within the context of geotechnical and mining engineering applications. Geometric optimisation of slopes such as those in open cut mines is important to reduce the overhead operational cost involved in construction, excavation and rehabilitation backfilling, while ensuring stability at an acceptable level. This is achieved by developing a unified platform combining genetic algorithm (GA) with scaled boundary finite element formulations and image-based meshing procedures. Since the image-based mesh generation procedure is an automatic process, it enables automation of the optimisation, which is an iterative proceeding. The capabilities of this technique are demonstrated by optimising the geometric parameters of complex slopes for given safety factors and rehabilitation geometries for given safety factors during a given construction period. The image-based SBFEM analysis platform is further developed to consider geological uncertainty, such as stratigraphic interfaces and phreatic surface fluctuations, so that their effect on slope stability can be studied. The Brownian bridge statistic technique is integrated into the pre-processing module to produce these instances reflecting the ranii dom fluctuations between two intervals and generate possible geological and hydrological cross-sections. This allows unknown geological stratigraphic interface fluctuation due to a lack of sublet information to be considered. The scaled boundary finite element formulations developed in the earlier parts of this thesis are used to discretise each generated profile and analysis probabilistically. Since the mesh generation method is fully automatic, this probabilistic analysis procedure enables to analyse of a large number of possible variations and their effect on geotechnical structures with limited human intervention. Few parametric studies were conducted on slopes to study the impact of stratigraphic and phreatic surface fluctuation on the probability of failure. Finally, the hydraulic fracture commonly seen in geotechnical and mining engineering applications is considered. The phase field has the potential to model complex fracture mechanisms including crack nucleation, branching and coalescence. However, it requires a very fine mesh in order to accurately regularise the energy resulting from the creation of new crack faces. This leads to longer processing time and high computational requirements. Moreover, fracture propagation modelling with phase field models requires equilibrium iterations and hence repetitive calculation of element matrices. This research develops a scaled boundary finite element formulation with phase field model to address hydraulic fracture problems in fully-saturated poro-elastic media. Adaptive meshing refinement based on quadtree meshes is applied. This restricts the fine mesh requirement to only the regions where damage is present and avoids the need for a very fine mesh throughout the structure. Further, leveraging from the unique number of patterns in a hierarchical mesh, an appropriate scaling technique is applied to transform the relevant matrices and vectors to the physical cell in the mesh. This avoids the need for repetitive calculations during the equilibrium iterations. These features increase the efficiency of fracture modelling while reducing the computational requirement. The benchmark problems and complex fracture network problems are provided to highlight the advantage of the method.
- Description: Doctor of Philosophy
Adaptive modelling of dynamic brittle fracture - a combined phase field regularized cohesive zone model and scaled boundary finite element approach
- Authors: Natarajan, Sundararajan , Ooi, Ean Tat , Birk, Carolin , Song, Chongmin
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal of Fracture Vol. 236, no. 1 (2022), p. 87-108
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- Description: Based on the error indicator computed from the scaled boundary equations, a quadtree based adaptive phase-field method is proposed for dynamic brittle fracture problems in isotropic material using the scaled boundary finite element method (SBFEM). The use of SBFEM alleviates the need for additional: (a) constraints to handle hanging nodes resulting from adaptive refinement and (b) post-processing techniques. Three representative examples are solved to demonstrate the efficiency of the proposed approach. From the numerical study, it is opined that the proposed approach requires an order of magnitude fewer degrees of freedom when compared to uniform refinement and can capture the crack morphology under dynamic loading conditions without compromising accuracy. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Automatic mesoscopic fracture modelling of concrete based on enriched SBFEM space and quad-tree mesh
- Authors: Jiang, Shouyan , Sun, Liguo , Ooi, Ean Tat , Ghaemian, Mohsen , Du, Chengbin
- Date: 2022
- Type: Text , Journal article
- Relation: Construction and Building Materials Vol. 350, no. (2022), p.
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- Description: A novel approach for mesoscale modelling of concrete composites is proposed by combining enriched scaled boundary finite element methods with quad-tree mesh. The concrete meso-structures are comprised of randomly distributed aggregates, mortar matrix, and interface transition zone. An improved random aggregate generation technique is developed to construct digital images of mesoscale concrete models. Based on the quadtree decomposition algorithm, meshes can be generated automatically from the digital images of concrete mesostructure. The whole mesh generation process is highly efficient without any artificial interference and eliminates the issue of hanging nodes faced by standard finite elements. Additionally, local remeshing is unnecessary as crack propagates. Three numerical examples are modelled to demonstrate the performance of the proposed approach, and the effects of aggregate area fraction on the mechanical properties of concrete composites are also discussed. © 2022 Elsevier Ltd
Development of the scaled boundary finite element method for image-based slope stability analysis
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Song, Chongmin , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: Computers and Geotechnics Vol. 143, no. (2022), p.
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- Description: This paper presents a numerical technique for geotechnical slope stability analysis, integrating digital image meshing with the scaled boundary finite element method, allowing site conditions such as complex stratigraphies, surface and internal geometry evolution to be simulated in a robust and straightforward procedure. The quadtree decomposition technique is used to automatically discretise the geometry directly from digital images using pixel information to accurately capture boundaries with fine-scale elements. The process allows complex numerical models to be generated from cross-section images of slopes, capitalising on the combination of the scaled boundary finite element method and quadtree meshing. The spatial distribution of the soil material properties can be represented by the colour of each pixel. A mapping technique is developed to integrate these parameters into the computational mesh. The feasibility of the proposed method is presented through case study simulations of an active large Australian open-pit mine, considering various aspects of complex features such as geometry, stratigraphy and material behaviour. © 2021
Simultaneous slope design optimisation and stability assessment using a genetic algorithm and a fully automatic image-based analysis
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Song, Chongmin , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal for Numerical and Analytical Methods in Geomechanics Vol. 46, no. 15 (2022), p. 2868-2892
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- Description: Mine slope design is a complex task that requires consideration of geotechnical analysis, structural stability, economics and the environment. Economic factors usually drive mine slope design, particularly in the case of open-pit designs, where the process of steepening slope walls by several degrees can have profound financial implications. Due to the risks associated with catastrophic slope collapse, slope stability analysis is an integral component of open-pit engineering projects. However, initial design concepts and geotechnical assessments are often considered separately. In this study, a technique is developed that combines the scaled boundary finite element method (SBFEM) with genetic algorithms (GAs) to simultaneously perform slope stability analysis and optimise the slope profile. The iterative design approach optimises characteristics of the slope profile such as the slope height, width, angle and number of benches while ensuring the factor of safety (FoS) remains above a threshold value. A salient feature of the technique is the ability to automatically address the modifications to the geometry of the slope by updating the digital images used in the analysis to assess the stability of each instance in the optimisation process and determine the optimum slope geometry. The results highlight the application of the developed technique to determine appropriate slope excavation designs as well as slope backfilling scenarios. The method is exemplified in several cases where complex stratigraphies and spatially variable materials are considered. As such, the GA-driven slope design process conveys an optimised, automated tool, combining mine slope design and slope stability analysis. © 2022 John Wiley & Sons Ltd.
A direct time-domain procedure for the seismic analysis of dam–foundation–reservoir systems using the scaled boundary finite element method
- Authors: Qu, Yanling , Chen, Denghong , Liu, Lei , Ooi, Ean Tat , Eisenträger, Sascha , Song, Chongmin
- Date: 2021
- Type: Text , Journal article
- Relation: Computers and Geotechnics Vol. 138, no. (2021), p.
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- Description: In this paper, a direct time-domain procedure for the seismic analysis of dam–reservoir–foundation interactions is presented based on the scaled boundary finite element method (SBFEM). The SBFEM is a semi-analytical method and requires the discretization of boundary only. The geometric complexity in the bounded dam–reservoir–foundation system is easily handled in the SBFEM using quadtree meshes where each structural component can be discretized independently. The elastic wave fields in the unbounded foundation are rigorously captured through SBFE solutions in terms of displacement unit-impulse response functions, while the acoustic wave propagation in the semi-infinite reservoir is modelled by the SBFE-based doubly asymptotic open boundary. The input of seismic excitations is addressed by incorporating the Domain Reduction Method (DRM) into the SBFEM. Cracks are modelled efficiently and accurately by combining the SBFEM and quadtree meshes. The accuracy and efficiency of the proposed methodology is investigated by studying several benchmarks, Pine Flat dam and Jin'anqiao dam. © 2021 Elsevier Ltd
Application of adaptive phase-field scaled boundary finite element method for functionally graded materials
- Authors: Pramod, Aladurthi , Hirshikesh , Natarajan, Sundararajan , Ooi, Ean Tat
- Date: 2021
- Type: Text , Journal article
- Relation: International Journal of Computational Methods Vol. 18, no. 3 (2021), p.
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- Description: In this paper, an adaptive phase-field scaled boundary finite element method for fracture in functionally graded material (FGM) is presented. The model accounts for spatial variation in the material and fracture properties. The quadtree decomposition is adopted for refinement, and the refinement is based on an error indicator evaluated directly from the solutions of the scaled boundary finite element method. This combination makes it a suitable choice to study fracture using the phase field method, as it reduces the mesh burden. A few standard benchmark numerical examples are solved to demonstrate the improvement in computational efficiency in terms of the number of degrees of freedom. © 2021 World Scientific Publishing Company.
Robust modelling of implicit interfaces by the scaled boundary finite element method
- Authors: Dsouza, Shaima , Pramod, A. L. N. , Ooi, Ean Tat , Song, Chongming , Natarajan, Sundararajan
- Date: 2021
- Type: Text , Journal article
- Relation: Engineering Analysis with Boundary Elements Vol. 124, no. (2021), p. 266-286
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- Description: In this paper, we propose a robust framework based on the scaled boundary finite element method to model implicit interfaces in two-dimensional differential equations in nonhomegeneous media. The salient features of the proposed work are: (a) interfaces can be implicitly defined and need not conform to the background mesh; (b) Dirichlet boundary conditions can be imposed directly along the interface; (c) does not require special numerical integration technique to compute the bilinear and the linear forms and (d) can work with an efficient local mesh refinement using hierarchical background meshes. Numerical examples involving straight interface, circular interface and moving interface problems are solved to validate the proposed technique. Further, the presented technique is compared with conforming finite element method in terms of accuracy and convergence. From the numerical studies, it is seen that the proposed framework yields solutions whose error is O(h2) in L2 norm and O(h) in the H1 semi-norm. Further the condition number increases with the mesh size similar to the FEM. © 2021 Elsevier Ltd
Treatment of multiple input uncertainties using the scaled boundary finite element method
- Authors: Dsouza, Shaima , Varghese, Tittu , Ooi, Ean Tat , Natarajan, Sundararajan , Bordas, Stephane
- Date: 2021
- Type: Text , Journal article
- Relation: Applied Mathematical Modelling Vol. 99, no. (2021), p. 538-554
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- Description: This paper presents a non-intrusive scaled boundary finite element method to consider multiple input uncertainties, viz., material and geometry. The types of geometric uncertainties considered include the shape and size of inclusions. The inclusions are implicitly defined, and a robust framework is presented to treat the interfaces, which does not require explicit generation of a conforming mesh or special enrichment techniques. A polynomial chaos expansion is used to represent the input and the output uncertainties. The efficiency and the accuracy of the proposed framework are elucidated in detail with a few problems by comparing the results with the conventional Monte Carlo method. A sensitivity analysis based on Sobol’ indices using the developed framework is presented to identify the critical input parameter that has a higher influence on the output response. © 2021 Elsevier Inc.
A combined virtual element method and the scaled boundary finite element method for linear elastic fracture mechanics
- Authors: Adak, Dibyendu , Pramod, ALN , Ooi, Ean Tat , Natarajan, Sundararajan
- Date: 2020
- Type: Text , Journal article
- Relation: Engineering Analysis with Boundary Elements Vol. 113, no. (2020), p. 9-16
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- Description: In this paper, we propose a framework that combines the recently introduced virtual element method (VEM) and the scaled boundary finite element method (SBFEM) to evaluate the fracture parameters. The domain is discretized with arbitrary polygons and the element that contains the crack tip is treated within the framework of the SBFEM. This facilitates a semi-analytical treatment of the crack tip singularity allowing the fracture parameters are estimated directly from the definition. The VEM is employed for the rest of the domain. The salient feature of the VEM is that the terms in the stiffness matrix are computed without requiring higher order quadrature schemes. As both the methods satisfy partition of unity and the compatibility condition, the matrices are assembled as in the conventional FEM. The accuracy of the proposed formulation is demonstrated with two standard benchmark examples. The proposed VEM-SBFEM framework yields accurate results. © 2019 Elsevier Ltd
A dual scaled boundary finite element formulation over arbitrary faceted star convex polyhedra
- Authors: Ooi, Ean Tat , Saputra, Albert , Natarajan, Sundararajan , Ooi, Ean Hin , Song, Chongmin
- Date: 2020
- Type: Text , Journal article
- Relation: Computational Mechanics Vol. 66, no. 1 (2020), p. 27-47
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- Description: A novel technique to formulate arbritrary faceted polyhedral elements in three-dimensions is presented. The formulation is applicable for arbitrary faceted polyhedra, provided that a scaling requirement is satisfied and the polyhedron facets are planar. A triangulation process can be applied to non-planar facets to generate an admissible geometry. The formulation adopts two separate scaled boundary coordinate systems with respect to: (i) a scaling centre located within a polyhedron and; (ii) a scaling centre on a polyhedron’s facets. The polyhedron geometry is scaled with respect to both the scaling centres. Polygonal shape functions are derived using the scaled boundary finite element method on the polyhedron facets. The stiffness matrix of a polyhedron is obtained semi-analytically. Numerical integration is required only for the line elements that discretise the polyhedron boundaries. The new formulation passes the patch test. Application of the new formulation in computational solid mechanics is demonstrated using a few numerical benchmarks. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
A polygon scaled boundary finite element formulation for transient coupled thermoelastic fracture problems
- Authors: Ooi, Ean Tat , Iqbal, M. , Birk, C. , Natarajan, Sundararajan , Ooi, E. H. , Song, C.
- Date: 2020
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 240, no. (2020), p.
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- Description: The scaled boundary finite element method is developed for transient thermoelastic fracture analysis. To enable this, a set of novel shape functions are derived considering thermoelastic equilibrium. The salient features of the proposed framework are: (a) can be formulated on polygons with an arbitrary number of sides leading to flexible mesh generation and (b) facilitates an accurate and direct evaluation of the stress intensity factors from their definition without resorting to any post-processing techniques using relatively coarse meshes. Several numerical benchmark problems demonstrate the aforementioned features of the technique. © 2020 Elsevier Ltd
Adaptive analysis using scaled boundary finite element method in 3D
- Authors: Zhang, Junqi , Natarajan, Sundararajan , Ooi, Ean Tat , Song, Chongmin
- Date: 2020
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 372, no. (2020), p.
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- Description: In this paper, an adaptive refinement technique using the scaled boundary finite element method (SBFEM) is proposed. The salient feature of this technique is that it is not required to regenerate the mesh for the whole model during the iterations. To this end, a local mesh refinement strategy is implemented based on a polytree algorithm in three dimensions, which can be applied to polyhedral elements with arbitrary number of nodes, edges and faces. These elements constructed by the SBFEM can be used in analysis with their boundaries discretized only, which reduce the difficulty to connect elements with different sizes. An explicit residual based error indicator is developed using the discontinuity of the stress field to guide the adaptive mesh refinement. The accuracy and efficiency of the proposed method are demonstrated using five numerical examples, including complex geometry and stress singularity. © 2020 Elsevier B.V.
- Description: The work presented in this paper is partially supported by the Australian Research Council through Grant Number DP180101538 .
An efficient forward propagation of multiple random fields using a stochastic Galerkin scaled boundary finite element method
- Authors: Mathew, Tittu , Pramod, A. L. N. , Ooi, Ean Tat , Natarajan, Sundararajan
- Date: 2020
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 367, no. (2020), p.
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- Description: This paper serves to extend the existing literature on the Stochastic Galerkin Scaled Boundary Finite Element Method (SGSBFEM) in two ways. The first part of this work deals with the formulation of multiple non-correlated Gaussian random fields using the conventional Karhunen–Loéve expansion technique and its forward propagation through the Spectral Stochastic Scaled Boundary Finite Element setting using the polynomial surface fit method in terms of the scaled boundary coordinates. The advantages in adopting such a forward propagation technique in capturing the statistical moments of Quantities of Interest (QoI) across the domain, are highlighted using carefully chosen linear elastic problems having large to least correlated random fields as inputs. The second contribution is the extension of the proposed forward Uncertainty Quantification (UQ) to take into account multiple independent random fields, followed by Polynomial Chaos Expansion (PCE) based sensitivity analysis. Both the computational efficiency and the accuracy of the proposed framework under different input random field correlation settings are elaborated upon by comparing their results against that obtained using the current existing SGSBFEM in the literature. Moreover, the stochastic results are validated for all the numerical examples using the Monte Carlo method. © 2020 Elsevier B.V.
Application of scaled boundary finite element method for delamination analysis of composite laminates using cohesive zone modelling
- Authors: Garg, Nikhil , Prusty, Gangadhara , Ooi, Ean Tat , Song, Chongmin , Pearce, Garth , Phillips, Andrew
- Date: 2020
- Type: Text , Journal article
- Relation: Composite Structures Vol. 253, no. (2020), p. 1-10
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- Description: In this paper, the scaled boundary finite element method (SBFEM) is evaluated for two-dimensional delamination analysis of composite laminates. The delamination phenomenon was studied using cohesive zone modelling (CZM). A bi-linear (triangular) traction-separation law was used to describe the interface behaviour, which was modelled using zero-thickness interface elements. Local arc-length solution technique was used to solve the non-linearity due to the interface behaviour. In this research, pure Mode I and Mode II as well as mixed mode delamination studies have been conducted using the SBFEM formulation. A variety of numerical experiments were performed. Good agreement was observed between the SBFEM simulation and the available numerical and experimental results in the open literature. A comparison between the SBFEM and other traditional methods shows that the presented formulation can solve the same physical problem with a reduction in the computational cost by more than half. The study highlights the advantages of SBFEM over other methods for modelling delamination in composite laminates using CZM.
- Description: This project is conducted within the ARC Training Centre for Automated Manufacture of Advanced Composites (IC160100040), supported by the Commonwealth of Australia under the Australian Research Council's Industrial Transformation Research Program.
A quadtree-polygon-based scaled boundary finite element method for image-based mesoscale fracture modelling in concrete
- Authors: Guo, H. , Ooi, Ean Tat , Saputra, Albert , Yang, Zhenjun , Natarajan, Sundararajan , Ooi, Ean Hin , Song, Chongmin
- Date: 2019
- Type: Text , Journal article , acceptedVersion
- Relation: Engineering Fracture Mechanics Vol. 211, no. (2019), p. 420-441
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- Description: A quadtree-polygon scaled boundary finite element-based approach for image-based modelling of concrete fracture at the mesoscale is developed. Digital images representing the two-phase mesostructure of concrete, which comprises of coarse aggregates and mortar are either generated using a take-and-place algorithm with a user-defined aggregate volume ratio or obtained from X-ray computed tomography as an input. The digital images are automatically discretised for analysis by applying a balanced quadtree decomposition in combination with a smoothing operation. The scaled boundary finite element method is applied to model the constituents in the concrete mesostructure. A quadtree formulation within the framework of the scaled boundary finite element method is advantageous in that the displacement compatibility between the cells are automatically preserved even in the presence of hanging nodes. Moreover, the geometric flexibility of the scaled boundary finite element method facilitates the use of arbitrary sided polygons, allowing better representation of the aggregate boundaries. The computational burden is significantly reduced as there are only finite number of cell types in a balanced quadtree mesh. The cells in the mesh are connected to each other using cohesive interface elements with appropriate softening laws to model the fracture of the mesostructure. Parametric studies are carried out on concrete specimens subjected to uniaxial tension to investigate the effects of various parameters e.g. aggregate size distribution, porosity and aggregate volume ratio on the fracture of concrete at the meso-scale. Mesoscale fracture of concrete specimens obtained from X-ray computed tomography scans are carried out to demonstrate its feasibility.
Adaptive phase-field modeling of brittle fracture using the scaled boundary finite element method
- Authors: Hirshikesh , Pramod, Aladurthi , Annabattula, Ratna , Ooi, Ean Tat , Song, Chongmin , Natarajan, Sundararajan
- Date: 2019
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 355, no. (2019), p. 284-307
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- Description: In this work, we propose an adaptive phase field method (PFM) to simulate quasi-static brittle fracture problems. The phase field equations are solved using the scaled boundary finite element method (SBFEM). The adaptive refinement strategy is based on an error indicator evaluated directly from the solutions of the SBFEM without any need for stress recovery techniques. Quadtree meshes are adapted to perform mesh refinement. The polygons with hanging nodes in the quadtree decomposition are treated as n−sided polygons within the framework of the SBFEM and do not require any special treatment in contrast to the conventional finite element method. Several benchmark problems are used to demonstrate the robustness and the efficacy of the proposed technique. The adaptive refinement strategy reduces the mesh burden when adopting the PFM to model fracture. Numerical results show an improvement in the computational efficiency in terms of the number of elements required in the standard PFM without compromising the accuracy of the solution.