An integrated design-analysis framework for three dimensional composite panels

We present an integrated design-analysis framework for three dimensional composite panels. The main components of the proposed framework consist of (1) a new curve/surface offset algorithm and (2) the isogeometric concept recently emerged in the computational mechanics community. Using the presented approach, finite element analysis of composite panels can be performed with the only input is the geometry representation of the composite surface. In this paper, non-uniform rational B-splines (NURBS) are used to represent the panel surfaces. A stress analysis of curved composite panel with stiffeners is provided to demonstrate the proposed framework

Crack growth modelling: enriched continuum vs. discrete models

Failure in quasi-brittle materials usually appears in the form of narrow bands called fracture process zones, where all inelastic deformation takes place, while the surrounding bulk material outside those areas typically unloads elastically. This localised nature of failure is the main source of size effects in these materials, since the width of the fracture process zone is a material property that does not scale with the size of the material volume. An adequate description of localised failure and associated size effects requires both size and behaviour of the fracture process zone and neighbouring material to be properly taken into account. In this study, we present two alternative approaches for modelling localised failure and simulating fracture propagation using finite element methods. In the first approach, an embedded crack appears at a constitutive level by enriching the kinematics of constitutive models, while in the second one this is done at the finite element level using cohesive interface elements. The advantages and shortcomings of both are presented through one numerical example on the failure of fibre-reinforced composite materials

Homogenization-based multiscale crack modelling: from micro-diffusive damage to macro-cracks

The existence of a representative volume element (RVE) for a class of quasi-brittle materials having a random heterogeneous microstructure in tensile, shear and mixed mode loading is demonstrated by deriving traction–separation relations, which are objective with respect to RVE size. A computational homogenization based multiscale crack modelling framework, implemented in an FE2 setting, for quasi-brittle solids with complex random microstructure is presented. The objectivity of the macroscopic response to the micro-sample size is shown by numerical simulations. Therefore, a homogenization scheme, which is objective with respect to macroscopic discretization and microscopic sample size, is devised. Numerical examples including a comparison with direct numerical simulation are given to demonstrate the performance of the proposed method.Peer ReviewedPostprint (author's final draft

Computational homogenization for multiscale crack modeling: implementational and computational aspects

This is the peer reviewed version of the following article: [Nguyen, V. P., Lloberas-Valls, O., Stroeven, M. and Sluys, L. J. (2012), Computational homogenization for multiscale crack modeling. Implementational and computational aspects. Int. J. Numer. Meth. Engng, 89: 192–226. doi:10.1002/nme.3237], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.3237/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingA computational homogenization procedure for cohesive and adhesive crack modeling of materials with a heterogeneous microstructure has been recently presented in Computer Methods in Applied Mechanics and Engineering (2010, DOI:10.1016/j.cma.2010.10.013). The macroscopic material properties of the cohesive cracks are obtained from the inelastic deformation manifested in a localization band (modeled with a continuum damage theory) at the microscopic scale. The macroscopic behavior of the adhesive crack is derived from the response of a microscale sample representing the microstructure inside the adhesive crack. In this manuscript, we extend the theory presented in Computer Methods in Applied Mechanics and Engineering (2010, DOI:10.1016/j.cma.2010.10.013) with implementation details, solutions for cyclic loading, crack propagation, numerical analysis of the convergence characteristics of the multiscale method, and treatment of macroscopic snapback in a multiscale simulation. Numerical examples including crack growth simulations with extended finite elements are given to demonstrate the performance of the methodPeer ReviewedPostprint (author's final draft

ViCLEVR: A Visual Reasoning Dataset and Hybrid Multimodal Fusion Model for Visual Question Answering in Vietnamese

In recent years, Visual Question Answering (VQA) has gained significant attention for its diverse applications, including intelligent car assistance, aiding visually impaired individuals, and document image information retrieval using natural language queries. VQA requires effective integration of information from questions and images to generate accurate answers. Neural models for VQA have made remarkable progress on large-scale datasets, with a primary focus on resource-rich languages like English. To address this, we introduce the ViCLEVR dataset, a pioneering collection for evaluating various visual reasoning capabilities in Vietnamese while mitigating biases. The dataset comprises over 26,000 images and 30,000 question-answer pairs (QAs), each question annotated to specify the type of reasoning involved. Leveraging this dataset, we conduct a comprehensive analysis of contemporary visual reasoning systems, offering valuable insights into their strengths and limitations. Furthermore, we present PhoVIT, a comprehensive multimodal fusion that identifies objects in images based on questions. The architecture effectively employs transformers to enable simultaneous reasoning over textual and visual data, merging both modalities at an early model stage. The experimental findings demonstrate that our proposed model achieves state-of-the-art performance across four evaluation metrics. The accompanying code and dataset have been made publicly accessible at \url{https://github.com/kvt0012/ViCLEVR}. This provision seeks to stimulate advancements within the research community, fostering the development of more multimodal fusion algorithms, specifically tailored to address the nuances of low-resource languages, exemplified by Vietnamese.Comment: A pre-print version and submitted to journa

On the existence of representative volumes for softening quasi-brittle materials: a failure zone averaging scheme

The concept of the representative volume element (RVE) for softening materials is revised in this contribution. It is demonstrated by means of numerical simulations that there exists a sample which is statistically representative for quasi-brittle materials with random microstructure like concrete. This finding is an important ingredient for homogenization-based multiscale modelling of softening materials.Peer ReviewedPostprint (author's final draft

About an approximate method to solve the static boundary value problems in the isotropic hardening elastic-plastic solid

The paper presents the theory, model, weak form, finite element method and return-mapping algorithm for the isotropic hardening elastic-plastic problem. Then applying the algorithm to numerically simulate a variety of plane strain problems