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Munro, D.P. (author), Ayas, C. (author), Langelaar, Matthijs (author), van Keulen, A. (author)We study linearity assumptions in the transient macroscale mechanical aspect of additive manufacturing (AM) process simulation. Linearity assumptions are often resorted to in combination with calibrated inelastic deformation components to arrive at computationally tractable yet reasonably accurate AM process models. We point out that...journal article 2019
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Keyvani Janbahan, A. (author), Tamer, M.S. (author), van Wingerden, J.W. (author), Goosen, J.F.L. (author), van Keulen, A. (author)Many investigations have focused on steady-state nonlinear dynamics of cantilevers in tapping mode atomic force microscopy (TM-AFM). However, a transient dynamic model—which is essential for a model-based control design—is still missing. In this paper, we derive a mathematical model which covers both the transient and steady-state behavior....journal article 2019
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van den Boom, S.J. (author), Zhang, J. (author), van Keulen, A. (author), Aragon, A.M. (author)Generating matching meshes for finite element analysis is not always a convenient choice, for instance, in cases where the location of the boundary is not known a priori or when the boundary has a complex shape. In such cases, enriched finite element methods can be used to describe the geometric features independently from the mesh. The...journal article 2019
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Sinico, M. (author), Ranjan, R. (author), Moshiri, M. (author), Ayas, C. (author), Langelaar, Matthijs (author), Witvrouw, A. (author), van Keulen, A. (author), Dewulf, W. (author)The Additive Manufacturing (AM) of injection molding inserts has gained popularity during recent years primarily due to the reduced design-to-production time and form freedom offered by AM. In this paper, Topology Optimization (TO) is performed on a metallic mold insert which is to be produced by the Laser Powder Bed Fusion (LPBF) technique....conference paper 2019
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Paggi, Umberto (author), Ranjan, R. (author), Thijs, Lore (author), Ayas, C. (author), Langelaar, Matthijs (author), van Keulen, A. (author), van Hooreweder, Brecht (author)In Laser Powder Bed Fusion (LPBF), the downfacing surfaces usually have increased surface roughness and reduced dimensional accuracy due to local overheating and warpage. To partially overcome this a new supporting structure is developed in this study, namely the contactless support. This is a thin blade parallel to the critical area which...conference paper 2019
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Wang, W. (author), Munro, D.P. (author), Wang, C.C. (author), van Keulen, A. (author), Wu, J. (author)The design of optimal structures and the planning of (additive manufacturing) fabrication sequences have been considered typically as two separate tasks that are performed consecutively. In the light of recent advances in robot-assisted (wire-arc) additive manufacturing which enable addition of material along curved surfaces, we present a...journal article 2019
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- van de Ven, E.A. (author), Langelaar, Matthijs (author), Ayas, C. (author), Maas, Robert (author), van Keulen, A. (author) abstract 2018
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- Zhang, Y. (author), Wang, Q. (author), Tichem, M. (author), van Keulen, A. (author) abstract 2018
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- van Keulen, A. (author), Ahsmann, A.W.M. (author), van den Akker, Evert (author), Habraken, Milou (author), Burghardt, Paul (author), Jayawardhana, Bayu (author), Van Lente, Harro (author), Meinders, Timo (author), Thuis, Bert (author), al., et. (author) report 2018
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Yang, Y. (author), Knol, Marius (author), van Keulen, A. (author), Ayas, C. (author)Selective laser melting (SLM) wherein a metal part is built in a layer-by-layer manner in a powder bed is a promising and versatile way for manufacturing components with complex geometry. However, components built by SLM suffer from substantial deformation of the part and residual stresses. Residual stresses arise due to temperature gradients...journal article 2018
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Sajadi, B. (author), Goosen, J.F.L. (author), van Keulen, A. (author)Electrostatic instability is one of the main features of many electrostatic MEMS and NEMS devices. In this paper, we investigate how the electrostatic instability of a plate-like electrode can be affected by a differential pressure. The results of this study indicate that the presence of differential pressure can have a significant influence...journal article 2018
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- Ranjan, R. (author), Ayas, C. (author), Langelaar, Matthijs (author), van Keulen, A. (author) conference paper 2018
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Keyvani Janbahan, A. (author), Sadeghian, Hamed (author), Goosen, J.F.L. (author), van Keulen, A. (author)The origin of amplitude reduction in Tapping Mode Atomic Force Microscopy (TM-AFM) is typically attributed to the shift in resonance frequency of the cantilever due to the nonlinear tip-sample interactions. In this paper, we present a different insight into the same problem which, besides explaining the amplitude reduction mechanism, provides...journal article 2018
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Gupta, D.K. (author), Langelaar, Matthijs (author), van Keulen, A. (author)Recent multiresolution topology optimization (MTO) approaches involve dividing finite elements into several density cells (voxels), thereby allowing a finer design description compared to a traditional FE-mesh-based design field. However, such formulations can generate discontinuous intra-element material distributions resembling QR-patterns....journal article 2018
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Sharma, Rahul (author), Zhang, J. (author), Langelaar, Matthijs (author), van Keulen, A. (author), Aragon, A.M. (author)In this paper, we propose a stress recovery procedure for low-order finite elements in 3D. For each finite element, the recovered stress field is obtained by satisfying equilibrium in an average sense and by projecting the directly calculated stress field onto a conveniently chosen space. Compared with existing recovery techniques, the...journal article 2018
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van de Ven, E.A. (author), Maas, Robert (author), Ayas, C. (author), Langelaar, Matthijs (author), van Keulen, A. (author)Additive manufacturing enables the nearly uncompromised production of optimized topologies. However, due to the overhang limitation, some designs require a large number of supporting structures to enable manufacturing. Because these supports are costly to build and difficult to remove, it is desirable to find alternative designs that do not...journal article 2018
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Verbart, A. (author), Langelaar, Matthijs (author), van Keulen, A. (author)In this paper, we propose a unified aggregation and relaxation approach for topology optimization with stress constraints. Following this approach, we first reformulate the original optimization problem with a design-dependent set of constraints into an equivalent optimization problem with a fixed design-independent set of constraints. The next...journal article 2017
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Sajadi, B. (author), Goosen, J.F.L. (author), van Keulen, A. (author)The electrostatic instability (pull-in) of a flat electrode in a parallel plate capacitor has been shown to be highly sensitive to external mechanical loads such as pressure. In this paper, we substantiate the possibility of prompting additional unstable configurations in such a system, with a remarkable sensitivity to the applied pressure....journal article 2017
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Wang, Q. (author), Goosen, J.F.L. (author), van Keulen, A. (author)Spanwise twist can dominate the deformation of flapping wings and alters the aerodynamic performance and power efficiency of flapping wings by changing the local angle of attack. Traditional Fluid–Structure Interaction (FSI) models, based on Computational Structural Dynamics (CSD) and Computational Fluid Dynamics (CFD), have been used to...journal article 2017
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Wang, Q. (author), Goosen, J.F.L. (author), van Keulen, A. (author)Flapping wings can pitch passively about their pitching axes due to their flexibility, inertia, and aerodynamic loads. A shift in the pitching axis location can dynamically alter the aerodynamic loads, which in turn changes the passive pitching motion and the flight efficiency. Therefore, it is of great interest to investigate the optimal...journal article 2017