Showing items 1 - 5 of 5

Automatic micro-scale modelling and evaluation of effective properties of highly porous ceramic matrix materials using the scaled boundary finite element method

- Tian, Xinran, Birk, Carolin, Du, Chengbin, Ooi, Ean Tat

  • Authors: Tian, Xinran , Birk, Carolin , Du, Chengbin , Ooi, Ean Tat
  • Date: 2024
  • Type: Text , Journal article
  • Relation: Computer Methods in Applied Mechanics and Engineering Vol. 419, no. (2024), p.
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  • Description: This paper presents an approach to the numerical estimation of effective properties of highly porous materials based on the scaled boundary finite element method (SBFEM). The latter can be formulated on quadtree meshes with hanging nodes and thus facilitates the efficient mesh generation and analysis of a large number of randomly created samples. To generate the corresponding Representative Volume Elements (RVEs), an improved Random Sequential Addition (RSA) method with overlap is used. Moreover, an alternative image-based digital matrix method for generating random assemblies of circular particles of the same size is proposed. In addition, a modified smoothing algorithm to treat the staircase boundaries present in a quadtree mesh is developed in order to accurately and efficiently capture the sinter-neck features of overlapping circular particles. The proposed image-based mesh generation and analysis procedure is used to evaluate the relationship between microstructural parameters and effective Young's modulus considering a large number of samples. In this context, a new dimensionless morphological parameter Nfc is proposed. The latter represents the morphology and connectivity of voids and is shown to be a useful indicator with respect to the effective elastic properties of highly porous ceramic matrix material. © 2023 Elsevier B.V.

Data-driven algorithm based on the scaled boundary finite element method and deep learning for the identification of multiple cracks in massive structures

- Jiang, Shouyan, Deng, Wangtao, Ooi, Ean Tat, Sun, Liguo, Du, Chengbin

  • Authors: Jiang, Shouyan , Deng, Wangtao , Ooi, Ean Tat , Sun, Liguo , Du, Chengbin
  • Date: 2024
  • Type: Text , Journal article
  • Relation: Computers and Structures Vol. 291, no. (2024), p.
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  • Description: Structural defect identification is a vital aspect of structural health monitoring used to assess the safety of engineering structures. However, quantitatively determining the dimensions of structural defects is often difficult. Therefore, this study presents an innovative data-driven algorithm that combines the scaled boundary finite element method (SBFEM) and a deep learning framework based on a dilated causal convolutional neural network (CNN) to identify crack-like defects in large-scale structures. The SBFEM is used to simulate different crack-like defects. Mesh generation is significantly simplified by a simple procedure that requires only changing the scale centre at the crack tip and the positions of the nodes at the crack opening. This minimises remeshing and enables simple generation of sufficient data to train the neural network. In addition, an absorbing boundary model based on Rayleigh damping is used to avoid computing the entire model when simulating wave propagation in massive structures. To ensure that sequential data remain ordered and to obtain a large receptive field without increasing the complexity of the neural network, a dilated causal CNN is employed in the deep learning framework. Therefore, more historical information is captured, and the complex mapping relationship between the echo signal and the crack information is efficiently learnt. The proposed model can accurately identify the number, location, and depth of cracks in massive structures. Moreover, it is robust to noise, which is demonstrated via numerical examples. Therefore, the proposed algorithm provides valuable insight into the detection and diagnosis of structural defects, which can ultimately improve the safety of engineering structures. © 2023 Elsevier Ltd

Dynamic fracture modeling of concrete composites based on nonlocal multiscale damage model and scaled boundary finite element methods

- Jiang, Shouyan, Lin, Anbang, Ooi, Ean Tat, Gao, Jia, Sun, Liguo, Du, Chengbin

  • Authors: Jiang, Shouyan , Lin, Anbang , Ooi, Ean Tat , Gao, Jia , Sun, Liguo , Du, Chengbin
  • Date: 2024
  • Type: Text , Journal article
  • Relation: Engineering Analysis with Boundary Elements Vol. 167, no. (2024), p.
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  • Description: Dynamic fracture is a critical concern in the design and reliability assessment of concrete structures. This study presents a numerical prediction of dynamic fractures in concrete composites using a nonlocal multiscale damage model and the scaled boundary finite element method (SBFEM). The nonlocal multiscale damage model accurately captures the damage behavior of concrete materials by considering the nonlocal effects and predicting fractures under dynamic loading conditions. The SBFEM combined with quadtree meshes, efficiently models and discretizes concrete composites, enhancing computational efficiency, and capturing local details. The concrete mesostructure consists of aggregates, mortar matrix, and interface transition zone. The random aggregates are generated using the popular Monte Carlo simulation and take-and-place methods. By slightly offsetting the boundaries of the generated aggregates, a virtual thickness interface is obtained to approximately characterize the weakest regions. This study extensively investigates the effects of loading rate, aggregate content and shape, and interface thickness on fracture properties. The loading rate significantly influences crack morphology, with low rates suppressing crack branching, and higher rates resulting in crack branching. Moreover, an increased aggregate content in the concrete results in greater maximum reaction force. Additionally, the range of the maximum reaction force is higher when polygonal aggregates are used as compared to circular aggregates. This study examines the impact of the interface thickness on the fracture characteristics. Increasing the interface thickness makes the interface region more fragile, resulting in additional minimally damaged areas alongside the completely damaged cracked sections. This behavior can be attributed to the energy degradation functions employed in the model, thereby decreasing the load-bearing capacity of these regions. These findings contribute to a better understanding of the dynamic fracture phenomena and aid in optimizing the design and improving the reliability of concrete structures. © 2024 Elsevier Ltd

Automatic mesoscopic fracture modelling of concrete based on enriched SBFEM space and quad-tree mesh

- Jiang, Shouyan, Sun, Liguo, Ooi, Ean Tat, Ghaemian, Mohsen, Du, Chengbin

  • 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

Modelling strong and weak discontinuities with the scaled boundary finite element method through enrichment

- Jiang, Shou-yan, Du, Chengbin, Ooi, Ean Tat

  • Authors: Jiang, Shou-yan , Du, Chengbin , Ooi, Ean Tat
  • Date: 2019
  • Type: Text , Journal article
  • Relation: Engineering Fracture Mechanics Vol. 222, no. (Dec 2019), p. 25
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  • Description: In this paper, a technique to model strong and weak discontinuities with the scaled boundary finite element method through enrichment is proposed. The main advantage of the method is that the enriched elements, in the spirit of the extended finite element method (XFEM), do not need to physically conform to the geometry of features, e.g. internal interfaces and cracks, and remeshing is unnecessary as the interfaces evolve. All the advantages of the SBFEM and the XFEM are retained. The stress singularity at the crack tip can be captured accurately and the stress intensity factors (SIFs) can be directly computed based on the singular displacement or stress at the crack tip within the framework of the SBFEM. The numerical properties and performance for the proposed method are assessed using several numerical examples. In particular, problems with discontinuities, e.g. voids, inclusions, and cracks are analysed. The results show that the accuracy and convergence rate of the new approach for solving void or inclusion problems are identical to those of the XFEM, but requires less number of degrees-of-freedom than the XFEM. For crack problems, compared with the XFEM with topological enrichment, the developed method is superior.
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