| 1. |
- Edelvik, Fredrik, 1972, et al.
(författare)
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Numerical homogenization of spatial network models
- 2024
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - 0045-7825 .- 1879-2138. ; 418
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Tidskriftsartikel (refereegranskat)abstract
- We present and analyze a methodology for numerical homogenization of spatial networks models, e.g. heat conduction and linear deformation in large networks of slender objects, such as paper fibers. The aim is to construct a coarse model of the problem that maintains high accuracy also on the micro-scale. By solving decoupled problems on local subgraphs we construct a low dimensional subspace of the solution space with good approximation properties. The coarse model of the network is expressed by a Galerkin formulation and can be used to perform simulations with different source and boundary data, at a low computational cost. We prove optimal convergence to the micro-scale solution of the proposed method under mild assumptions on the homogeneity, connectivity, and locality of the network on the coarse scale. The theoretical findings are numerically confirmed for both scalar-valued (heat conduction) and vector-valued (linear deformation) models.
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| 2. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Geometry Assurance Integrating Process Variation with Simulation of Spring-in for Composite Parts and Assemblies
- 2014
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Ingår i: Proc. of ASME 2014 International Mechanical Engineering Congress & Exposition. - 9780791846438 ; 2A
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Konferensbidrag (refereegranskat)abstract
- Geometrical variation and deviation in all manufacturing processes affect quality of the final product. Therefore geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed. Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper we present how to combine the process variation simulation of composites with traditional variation simulations. The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites,the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
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| 3. |
- Jareteg, Cornelia, 1986, et al.
(författare)
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Variation simulation for composite parts and assemblies including variation in fiber orientation and thickness
- 2014
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Ingår i: Procedia CIRP CATS 2014. 5th CATS 2014 - CIRP Conference on Assembly Technologies and Systems. - : Elsevier BV. - 2212-8271. ; 23, s. 235-240
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Konferensbidrag (refereegranskat)abstract
- All manufacturing processes are afflicted by geometrical variation, which can lead to defect products. A simulation tool for geometry assurance analysis is therefore important in the design process. The use of composites has recently increased drastically, but there is still a lack of understanding about the effects of variation in such parts. A method for predicting variation in subassemblies, including variation in fiber orientation and ply thickness for composites is presented. The approach is demonstrated on an industrial case and finite element analysis is used to calculate the deformation. In particular, contribution from variation in material properties to the variation in critical points is analyzed. The results indicate that material uncertainties have a small impact on the geometric variation for the test case.
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| 4. |
- Kettil, Gustav, 1990, et al.
(författare)
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Detailed Simulations of Early Paper Forming
- 2015
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Ingår i: COST FP1005 Fibre Suspension Flow Modelling Final Conference Trondheim 2015 June 9-11.
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Konferensbidrag (refereegranskat)abstract
- Computer simulations are important to increase the knowledge of the processes involved in paper making. Because of the complexity of the paper processes the development of simulation tools requires models and numerical methods which capture as much as possible of the real physical phenomena. In this paper a framework for simulation of fiber suspension flow is presented. The framework is founded on a fluid solver for the Navier-Stokes equations and a fiber model based on finite strain beam theory including shearing. Moreover, the coupling between fibers and fluid is resolved with the immersed boundary method and the interaction between the fibers is calculated using a model based on DLVO-theory.
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| 5. |
- Kettil, Gustav, 1990, et al.
(författare)
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Novel Contact Forces for Immersed Boundary Paper Forming Simulations
- 2015
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Ingår i: Online proceedings: http://tappi.sclivelearningcenter.com/; PF2 - The Past, Present and Future of CFD Papermaking; PaperCon 2015 Atlanta April 19-22.
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Konferensbidrag (refereegranskat)abstract
- To be able to simulate the different processes involved in paper machines, models, numerical methods and algorithms have to be developed which capture as much as possible of the real physical phenomena. In this paper a model for calculation of the chemical and physical interaction between objects included in a fiber suspension is presented. The contact force model is based on DLVO theory [1, 2] and uses so-called contact points distributed along the fiber suspension objects. The contact model has been used in an existing framework to simulate the build-up of low density paper webs. In the framework fibers are modeled as elliptical cylinders whose movements are described by finite-strain beam theory which includes shearing. The fluid flow is computed using a Navier-Stokes solver and immersed boundary methods are utilized to resolve the flow around each fiber. For validation, the air permeability and thickness of the paper webs have been measured and compared with simulated data. The result demonstrates that the software can be used to simulate paper forming.
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| 6. |
- Lorin, Samuel C, 1983, et al.
(författare)
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Simulating Geometrical Variation in Injection Molding
- 2010
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Ingår i: Proceedings of NordDesign2010 International Conference on Methods and Tools for Product and Production Development, August 25-27, Gothenburg, Sweden.. - 9789163370649 ; 8:2, s. 395-404
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Konferensbidrag (refereegranskat)
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| 7. |
- Svensson, Martin, 1987, et al.
(författare)
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Simulation of Droplet Jetting of a Non-Newtonian Mixed Suspension
- 2016
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Ingår i: ICMF-2016 – 9th International Conference on Multiphase Flow May 22nd – 27th 2016, Firenze, Italy.
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Konferensbidrag (refereegranskat)abstract
- The jet printing of a dense mixed non-Newtonian suspension is based on the rapid displacement of fluid through a nozzle, the forming of a droplet and eventually the break-off of the filament. The ability to model this process would facilitate the development of future jetting devices. The purpose of this study is to propose a novel simulation framework and to show that it captures the main effects such as droplet shape, volume and speed. In the framework, the time dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two phase system with the surrounding air being one phase and the dense suspension the other. Hence, the non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver and LaStFEM, a large strain FEM solver. Jetting behaviour was shown to be affected not only by piston motion and fluid rheology, but also by the energy loss in the jetting head. The simulation results were compared to experimental data obtained from an industrial jetting head.
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| 8. |
- Mark, Andreas, 1980, et al.
(författare)
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Optimisation of Robotised Sealing Stations in Paint Shops by Process Simulation and Automatic Path Planning
- 2014
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Ingår i: International Journal of Manufacturing Research. - 1750-0591 .- 1750-0605. ; 9:1, s. 4-26
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Tidskriftsartikel (refereegranskat)abstract
- Application of sealing materials is done in order to prevent water leakage into cavities of the car body, and to reduce noise. The complexity of the sealing spray process is characterised by multi-phase and free surface flows,multi-scale phenomena, and large moving geometries, which poses great challenges for mathematical modelling and simulation. The aim of this paper is to present a novel framework that includes detailed process simulation andautomatic generation of collision free robot paths. To verify the simulations, the resulting width, thickness and shape of applied material on test plates as a function of time and spraying distance have been compared to experiments. The agreement is in general very good. The efficient implementation makes it possible to simulate application of one meter of sealing material in less than anhour on a standard computer, and it is therefore feasible to include such detailed simulations in the production preparation process and off-line programming of the sealing robots.
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| 9. |
- Andersson, Björn O, 1982, et al.
(författare)
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A Modified TAB Model for Simulation of Atomization in Rotary Bell Spray Painting
- 2013
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Ingår i: Journal of Mechanical Engineering and Automation. - 2163-2413. ; 3:2, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- The Rotary bell spray applicator technique is commonly used in the automotive industry for paint application because of its high transfer efficiency and high-quality result. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization into small droplets where the resulting size distribution depends on the process conditions. Especially the rotation speed of the bell is an important parameter governing the size distribution. The main research question in this work is to investigate if the Taylor Analogy Breakup (TAB) model can be used to predict the resulting droplet size distributions in spray painting. As the paint is a viscous fluid a modification of the TAB model taking non-linear effects of large viscosity into account is proposed. The parameters in the breakup model are tuned by optimization to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The TAB method is able to quantitatively predict the result of the breakup process and can be used in a preprocessing stage of a full spray painting simulation, thereby reducing the need for costly and cumbersome measurements.
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| 10. |
- Andersson, Björn O, 1982, et al.
(författare)
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Modeling Surface Tension in SPH by Interface Reconstruction using Radial Basis Functions
- 2010
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Ingår i: Proceedings of the 5th International SPHERIC Workshop, 22-25 June 2010, Manchester, U.K., edited by B. D. Rogers. ; , s. 7-14
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A novel method for reconstructing the interface between two fluids is described and evaluated. The method uses a different basis for approximating the color function than what is common practice in SPH simulations. The key feature of the new method is the ability to omit small length scale structures in order to obtain a smoother representation. A smoother interface is more suitable to derive a surface tension force from, as the magnitude of the force is proportional to the curvature which is related to the second derivative along the interface.
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