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Item type:Publication, Access status: without files , Application of the Non-Negative Moment Fitting Approach in the Finite Cell Analysis of Brittle Phase-Field Fracture(World Scientific Publishing (WSPC), 2025-04-21); ; ; ; This paper addresses the prediction of fracture processes in complex geometries. In this approach, phase-field modeling is integrated into the finite cell method to have an efficient and robust simulation tool for brittle fracture. The non-negative moment fitting approach is employed as an integration scheme to reduce the number of integration points, which leads to shorter simulation times as well as lower memory requirements for history variables. Two 3D benchmark examples are provided to demonstrate the performance of the implemented approach compared to the standard quadrature based on the space-tree approach. Finally, the proposed method is applied to predict the sequence of strut fractures in brittle foams.Publicationtype: Journal Article132 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Structural analysis of small-scale 3D printed composite tidal turbine bladesThe existing research literature lacks comprehensive investigations into assessing the structural performance of marine renewable energy conversion devices, particularly 3D printed turbine blades, which often rely solely on computational modelling without experimental validation methods and/or established mechanical characterization techniques. This leads to significant uncertainty regarding the performance of 3D printed turbine blades manufactured by additive manufacturing technology. This study aims to fill this gap by proposing a procedure for evaluating the structural integrity of commercial small-scale tidal turbine blade (5 KW) manufactured using fused filament fabrication 3D printing with a linear infill pattern. This is achieved by developing a combined experimental, hydrodynamic, and finite element approach with the view to inspect the micro-mechanical properties of representative volume elements of 3D printed microstructures using homogenization technique. The results of mechanical testing and hydrodynamic modelling are used to create a finite element model of the 3D printed blade, allowing for stress and failure analysis. Findings indicate that while integrating 3D printed materials into blade design via 3D printing technology is feasible, the choice of materials is limited to high stiffness composite filaments. Finally, experimental validation of numerical results, particularly full field strain distribution maps obtained by digital image correlation technique for flexural testing and laboratory-scale 3D printed blade, confirms the accuracy of the finite element results. Finite element-based homogenization techniques provide valuable insights into potential failure modes in 3D printed tidal turbine blades. However, the expedited calculation of orthotropic properties through finite element analysis proves to be a faster mechanical characterization method compared to experimental approaches. The proposed methodology in this study facilitates quicker iterative design of 3D printed blades, thereby reducing the need for repeated experiments and ultimately lowering manufacturing costs.Publicationtype: Journal Article24 92 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Size effects of voids on the mechanical properties of 3D printed partsAlthough the effects of additive manufacturing process parameters on the mechanical properties of 3D printed parts have been numerically investigated in the literature, less attention has been paid on the size effects of voids between deposited filaments. This study fills this gap by developing a methodology based on a combined finite element (FE) and design of experiment (DoE) technique. The development of FE methodology is based on micro-mechanical analysis of representative volume element (RVE) of 3D printed parts to predict the effective orthotropic properties. To account for the size effects of inter-bead voids, the RVE includes contribution of the multiple parameters of layer heights, layer widths and overlapping regions. To study the main and interaction effects of the above input parameters on the stiffness properties of 3D printed parts, a structured approach based on full factorial design is used. Although the size effects of voids on the constituents of elastic moduli of RVE were investigated, the main focus in the present work is to develop a regression model to predict the stiffness properties. The FE stress analysis of the RVE conducted in this study provides an insight about the potential failure modes such as delamination and filament debonding that may occur in load bearing 3D printed parts. For a case study, the results of FE-based homogenization technique in terms of stiffness properties are validated against the experimental data via three-point bending and Iosipescu shear tests which were conducted in conjunction with digital image correlation technique. The combined numerical and statistical approach proposed in this study provides a swift iterative design of 3D printed parts prior to the time-consuming computation modelling, contributing to reduce the number of tests and manufacturing costs.Publicationtype: Journal Article13 91 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Acceleration of immersed computations of brittle phase‐field fracture utilizing moment fitting schemes(Wiley, 2024-03); ; ; ; Numerical methods play an important role when predicting structural failure in industrial applications. Among various methods, the phase‐field modeling (PFM) seems to be a very promising approach. By introducing an additional phase‐field variable, it can account for crack initiation, crack propagation, dynamic crack branching and more. However, it needs a very fine mesh especially along the propagating crack path. When utilizing boundary‐fitted methods such as the finite element method, this can lead to a large amount of elements and thus, results in huge systems of equations. In order to overcome this issue, immersed methods like the finite cell method (FCM) have been developed, where the mesh is independent of the geometry, which results in a fast and simple pre‐processing. In this work, the FCM is applied to the PFM in order to simulate quasi‐static brittle fracture of structures with complex geometries. Furthermore, the non‐negative moment fitting (NNMF) is employed in order to accelerate the finite cell computations. The proposed methods are tested on a numerical example in order to demonstrate the strength of the NNMF.Publicationtype: Conference Paper34 40 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Simulating brittle fracture with a robust hybrid explicit–implicit solver for staggered phase‐field problems(Wiley, 2024-03); ; ; ; In this work, the robustness of phase‐field fracture simulations is increased by introducing a new hybrid approach to take advantages of both explicit and implicit solvers. Switching to an explicit solver at critical load cases enables us to define a threshold on the maximum number of staggered iterations per load step. Having this threshold would be very useful in complicated FCM problems since we cannot wait for a full convergence of the implicit solver at critical load steps. With the new hybrid method, the problem is implicit as long as the implicit solver can converge within a specified threshold; otherwise, the failed load step will be solved robustly using an explicit approach. The method can resolve the highly nonlinear part of the global load–displacement curve. The superiority of the approach is shown in different benchmark examples.Publicationtype: Conference Paper11 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adaptive quadrature of trimmed finite elements and cells based on bezier approximation(World Scientific Publishing (WSPC), 2024-02-01); ; ; In this paper, a new boundary-conforming adaptive method for the numerical integration of trimmed elements is presented. The locations and weights of new integration points are determined based on special mapping formulations. The prerequisite of this technique is to describe the trimming curves/surfaces by parametric Bezier curves/surfaces within the parent element domain. The fitting error is under control, therefore the number of quadrature points for exact integration can be adjusted automatically based on the complexity of trimming curve and the corresponding integrand. The proposed method can be easily implemented into fictitious domain approaches. Different integration tasks as well as structural examples reveal that the proposed method delivers accurate and robust solutions for a wide variety of 2D/3D geometries with a rather low number of integration points.Publicationtype: Journal Article48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Accurate integration of trimmed cells based on Bezier approximationIn this work, a new adaptive integration method for simulation of two-dimensional linear elasticity problems is presented. The main benefit of the proposed method is the reduction of the computational cost by lowering the number of integration points required to reach a certain level of accuracy. The main concept of the proposed method is to calculate new weights for trimmed cells employing the advantage of Bezier parametric curves. Within this concept, it is possible to map a square to a triangle with one curved edge where any curved edge is approximated by a parametric Bezier curve. In this way, a new set of Gaussian quadrature points is introduced for each trimmed cell in a fast and robust way. Besides main mapping cases, the integration method includes supplementary cases as well to increase the robustness and generality of the method. In the next step, the proposed method is implemented in a two-dimensional fictitious domain code in MATLAB to solve structural problems. The results will be compared to those obtained through the commercial finite element code ABAQUS. It is shown that the proposed method is accurate and robust.Publicationtype: Conference Paper63 187