Browsing Faculty of Computing, Engineering and Media by Author "Abdi, Meisam"
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Item Open AccessDesign optimization for an additively manufactured automotive component(Inderscience Publishers, 2018-03-11) Abdi, Meisam; Ashcroft, Ian; Wildman, RickyThe aim of this paper is to investigate the design optimization and additive manufacture of automotive components. A Titanium brake pedal processed through Selective Laser Melting (SLM) is considered as a test case. Different design optimisation techniques have been employed including topology optimization and lattice structure design. Rather than using a conventional topology optimization method, a recently developed topology optimization method called Iso-XFEM is used in this work. This method is capable of generating high resolution topology optimised solutions using isolines/isosurfaces of a structural performance criterion and eXtended Finite Element Method (XFEM). Lattice structure design is the other technique used in this work for the design of the brake pedal. The idea is to increase the stability of the brake pedal to random loads applied to the foot pad area of the pedal. The use of lattice structures can also significantly reduce the high residual stress induced during the SLM process. The results suggest that the integration of the design optimization techniques with a metal additive manufacturing process enables development of a promising tool for producing lightweight energy efficient automotive components. Item Open AccessExploiting Generative Design for 3D Printing of Bacterial Biofilm Resistant Composite Devices(WILEY, 2021-05-29) He, Yinfeng; Abdi, Meisam; Trindade, Gustavo F.; Begines, Belén; Dubern, Jean-Frédéric; Prina, Elisabetta; Hook, Andrew L.; Choong, Gabriel Y. H.; Ledesma, Javier; Tuck, Christopher J.; Rose, Felicity R. A. J.; Hague, Richard J. M.; Roberts, Clive J.; De Focatiis, Davide S. A.; Ashcroft, Ian A.; Paul, Williams; Irvine, Derek J.; Alexander, Morgan R.; Wildman, Ricky D.As the understanding of disease grows, so does the opportunity for personalization of therapies targeted to the needs of the individual. To bring about a step change in the personalization of medical devices it is shown that multi-material inkjet-based 3D printing can meet this demand by combining functional materials, voxelated manufacturing, and algorithmic design. In this paper composite structures designed with both controlled deformation and reduced biofilm formation are manufactured using two formulations that are deposited selectively and separately. The bacterial biofilm coverage of the resulting composites is reduced by up to 75% compared to commonly used silicone rubbers, without the need for incorporating bioactives. Meanwhile, the composites can be tuned to meet user defined mechanical performance with ±10% deviation. Device manufacture is coupled to finite element modelling and a genetic algorithm that takes the user-specified mechanical deformation and computes the distribution of materials needed to meet this under given load constraints through a generative design process. Manufactured products are assessed against the mechanical and bacterial cell-instructive specifications and illustrate how multifunctional personalization can be achieved using generative design driven multi-material inkjet based 3D printing. Item Open AccessInsight into the mechanical properties of 3D printed strut-based lattice structures(Springer, 2022-12-15) Ali, Hafiz Muhammad Asad; Abdi, Meisam; Yong, SunSince the development of additive manufacturing (3D printing), there has been a growing interest in the use of 3D printed lattice structures for a range of mechanical and biomedical applications. This study investigates the elastic properties of different types of strut-based lattice structures obtained through a series of compression tests and compares them against numerically calculated properties of intended designs. Two different 3D printing processes are employed for the fabrication of lattice structures, including selective laser sintering (SLS) and digital light processing (DLP). Gibson-Ashby power-law for cellular structures has been initially utilised as a framework for the comparison of numerical and experimental results. The results are normalised, allowing the comparison of elastic properties of lattices made in different polymer materials independent of the bulk material properties. This study suggests that although the mechanical properties of the fabricated parts are heavily dependent on the design of lattice unit-cell, the mechanical properties can be significantly different to those of intended designs depending on the 3D printing process used for the fabrication of lattice structures. Item Open AccessInvestigation of passive oscillations of flexible splitter plates attached to a circular cylinder(Elsevier, 2018-11-23) Abdi, Rezvan; Rezazadeh, Niki; Abdi, MeisamThis paper presents a numerical study to address wake control of a circular cylinder subjected to two-dimensional laminar flow regime using single and multiple flexible splitter plates attached to the cylinder. Three different cases are presented in the study, covering cylinders with one, two and three horizontally attached splitter plates while the locations of the plates around the cylinders are varied. The length of the splitter plates was equal to the cylinder diameter and Reynolds number was 100. Due to the flexibility of the plates, the problem was modeled as a Fluid-Structure Interaction (FSI) problem and the commercial finite element software, Comsol Multiphysics, was utilized to solve this problem using Arbitrary Lagrangian–Eulerian (ALE) method. Vortex shedding frequency and fluid forces acting on the cylinder are investigated, along with a comprehensive parametric study to identify the optimum arrangement of the plates for maximum drag reduction and maximum vortex shedding frequency reduction. The numerical results associated to the flexible splitter plates are also compared with the corresponding rigid splitter plate cases investigated in a previous study. Moreover, the tip amplitude of the plates and the maximum strains were measured in order to find an optimum position for placing a piezoelectric polymer to harvest energy from the flow. Item Open AccessReduction of fluid forces and vortex shedding frequency of a circular cylinder using rigid splitter plates(Taylor and Francis, 2017-03-31) Abdi, Rezvan; Rezazadeh, Niki; Abdi, MeisamThis study investigates the fluid forces acting on a circular cylinder in a laminar flow regime while using a passive control strategy. Three cases including the cylinder with one, two or three rigid splitter plates attached at its rear surface were considered and the location of horizontal plates (attachment angle) was varied between 0° and 90°. A comprehensive parametric study was performed to identify the optimum arrangement of the plates using the commercial finite element software, Comsol Multiphysics. The results show that the location and the number of the plates have crucial effects on the wake control. Increasing the number of splitter plates from one to two symmetric parallel plates led to a reduction in drag force, vortex shedding frequency and fluctuation of lift force. A maximum drag reduction of 23% for dual-splitters and 15% for single-splitter was achieved, at an angle of 45° at Reynolds number 100. However, increasing the number of attached plates to three didn’t have a significant effect on flow quantities when plates of the same length were utilised. The suitability of the third plate (the middle plate) was further studied by investigating the effect of length of the plate on flow quantities. Item Metadata onlyStrategies for functionally graded lattice structures derived using topology optimisation for Additive Manufacturing(Elsevier, 2017-11-14) Panesar, Ajit; Abdi, Meisam; Hickman, Duncan; Ashcroft, IanA number of strategies that enable lattice structures to be derived from Topology Optimisation (TO) results suitable for Additive Manufacturing (AM) are presented. The proposed strategies are evaluated for mechanical performance and assessed for AM specific design related manufacturing considerations. From a manufacturing stand-point, support structure requirement decreases with increased extent of latticing, whereas the design-to-manufacture discrepancies and the processing efforts, both in terms of memory requirements and time, increase. Results from Finite Element (FE) analysis for the two loading scenarios considered: intended loading, and variability in loading, provide insight into the solution optimality and robustness of the design strategies. Lattice strategies that capitalised on TO results were found to be considerably (∼40–50%) superior in terms of specific stiffness when compared to the structures where this was not the case. The Graded strategy was found to be the most desirable from both the design and manufacturing perspective. The presented pros-and-cons for the various proposed design strategies aim to provide insight into their suitability in meeting the challenges faced by the AM design community. Item Open AccessTopology Optimization of Geometrically Nonlinear Structures using an Evolutionary Optimization Method(Taylor & Francis, 2017-01-19) Abdi, Meisam; Ashcroft, Ian; Wildman, RickyIso-XFEM method is an evolutionary optimization method developed in our previous studies to enable the generation of high resolution topology optimised designs suitable for additive manufacture. Conventional approaches for topology optimization require additional post-processing after optimization to generate a manufacturable topology with clearly defined smooth boundaries. Iso-XFEM aims to eliminate this time-consuming post-processing stage by defining the boundaries using isovalues of a structural performance criterion and an extended finite element method (XFEM) scheme. In this paper, the Iso-XFEM method is further developed to enable the topology optimization of geometrically nonlinear structures undergoing large deformations. This is achieved by implementing a total Lagrangian finite element formulation and defining a structural performance criterion appropriate for the objective function of the optimization problem. The Iso-XFEM solutions for geometrically nonlinear test-cases implementing linear and nonlinear modelling are compared, and the suitability of nonlinear modelling for the topology optimization of geometrically nonlinear structures is investigated.