Precision Casting via Advanced Simulation and Manufacturing

A two-year program was conducted to develop and commercially implement selected casting manufacturing technologies to enable significant reductions in the costs of castings, increase the complexity and dimensional accuracy of castings, and reduce the development times for delivery of high quality castings. The industry-led R&D project was cost shared with NASA's Aerospace Industry Technology Program (AITP). The Rocketdyne Division of Boeing North American, Inc. served as the team lead with participation from Lockheed Martin, Ford Motor Company, Howmet Corporation, PCC Airfoils, General Electric, UES, Inc., University of Alabama, Auburn University, Robinson, Inc., Aracor, and NASA-LeRC. The technical effort was organized into four distinct tasks. The accomplishments reported herein. Task 1.0 developed advanced simulation technology for core molding. Ford headed up this task. On this program, a specialized core machine was designed and built. Task 2.0 focused on intelligent process control for precision core molding. Howmet led this effort. The primary focus of these experimental efforts was to characterize the process parameters that have a strong impact on dimensional control issues of injection molded cores during their fabrication. Task 3.0 developed and applied rapid prototyping to produce near net shape castings. Rocketdyne was responsible for this task. CAD files were generated using reverse engineering, rapid prototype patterns were fabricated using SLS and SLA, and castings produced and evaluated. Task 4.0 was aimed at developing technology transfer. Rocketdyne coordinated this task. Casting related technology, explored and evaluated in the first three tasks of this program, was implemented into manufacturing processes

Mobility of Nano-Particles in Rock Based Micro-Models

A confocal micro-particle image velocimetry (C-μPIV) technique along with associated post-processing algorithms is detailed for obtaining three dimensional distributions of nano-particle velocity and concentrations at select locations of the 2.5D (pseudo 3D) Poly(methyl methacrylate) (PMMA) and ceramic micro-model. The designed and fabricated 2.5D micro-model incorporates microchannel networks with 3D wall structures with one at observation wall which resembles fourteen morphological and flow parameters to those of fully 3D actual reservoir rock (Boise Sandstone) at resolutions of 5 and 10 μm in depth and 5 and 25 μm on plane. In addition, an in-situ, non-destructive method for measuring the geometry of low and high resolution PMMA and ceramic micro-models, including its depth, is described and demonstrated. The flow experiments use 860 nm and 300 nm fluorescence-labeled polystyrene particles, and the data is acquired using confocal laser scanning microscopy. Regular fluorescence microscopy is used for the in-situ geometry measurement along with the use of Rhodamine dye and a depth-to-fluorescence-intensity calibration, which is linear. Monochromatic excitation at a wavelength of 544 nm (green) produced by a HeNe continuous wave laser was used to excite the fluorescence-labeled nanoparticles emitting at 612 nm (red). Confocal images were captured by a highly sensitive fluorescence detector photomultiplier tube. Results of detailed three dimensional velocity, particle concentration distributions, and particle deposition rates from experiments conducted at flow rates of 0.5 nL/min, 1 nL/min, 10 nL/min and 100 nL/min are presented and discussed. The three dimensional micro-model geometry reconstructed from fluorescence data is used as the computational domain to conduct numerical simulations of the flow in the as-tested micro-model for comparisons to experimental results using dimensionless Navier-Stokes model. The flow simulation results are also used to qualitatively compare with velocity distributions of the flowing particles at selected locations. The comparison is qualitative because the particle sizes used in these experiments may not accurately follow the flow itself given the geometry of the micro-models. These larger particles were used for proof of concept purposes, and the techniques and algorithms used permit future use of particles as small as 50 nm

Linking mould filling and structural simulations

Computer Aided Engineering (CAE) is common standard in the development process within the automotive industry. For thermoplastic components, for example, the manufacturing process is commonly simulated with injection moulding simulation software and passive safety with explicit crash software. Currently both disciplines are only linked within the simulation of fibre reinforced thermoplastics to take into account the fibre orientation from injection moulding simulation within crash simulation due to the significant influence of the fibre orientation on mechanical part properties. This work proposes a methodology that allows consideration of moulding conditions on the mechanical behaviour of unreinforced injection moulded components by coupling injection moulding simulation (Moldflow) and crash simulation (LS-DYNA (R)/RADIOSS (R)). A newly developed dedicated computer application allows to directly consider results from injection simulation within crash simulations. The manufacturing boundary conditions that most influence the mechanical behaviour are combined within the thermomechanical indices (TMI) methodology, and mapped onto each finite element within the crash simulation. Mathematical functions have been used to correlate the TMI to important mechanical properties of the moulded polymer. A user defined material model can read those indices and translate them to local mechanical properties.This work is funded by FEDER funds through the COMPETE 2020 program and National Funds through FCT under project UID/CTM/50025/2013, and grant SFRH/BD/51570/2011

Reduction of sink marks in wire insert molded parts

Integrating the huge wiring harness network with the plastic trim components found in the car is an attractive way to reduce the vehicle weight. When any foreign object is inserted in an injection molded part, the change in polymer cross section leads to sink marks which are aesthetic defects and are not acceptable for plastic trim components. In this thesis, a method to minimize or eliminate sink marks for wire insert molded component using injection molding process is presented. L9 Taguchi DOE experimental framework has been employed to study the effect of process parameters, part rib geometry, and the presence of wire itself on the sink mark formation. Sink depth is defined as the excess deflection in the surface profile which can be felt to hand. A descriptive simulation study is presented where process parameters namely, the mold temperature, the melt temperature, and the pack time are varied on different sets of rib geometry to observe the depth of a sink mark. The simulation results indicate that high mold temperature effectively minimizes the sink depth for all the rib geometries whereas the influence of melt temperature and pack time depends on the particular rib geometry. The results also testify that a proper combination of rib geometry and process parameters eliminates the sink mark

Additive Manufacturing of a Motorcycle Helmet Utilizing 7-Axis 3D Printing

This project analyzes the structural properties of 7-axis 3D printing versus traditional FDM printing. The team worked with AREVO Inc to manufacture a motorcycle helmet and test samples made from carbon fiber in a PEEK matrix. A drop-test rig was designed and constructed in-house to test a traditionally printed carbon fiber helmet alongside commercial helmets of identical geometry. The lighter weight printed helmet experienced significantly lower peak deceleration in the test headform (223 G’s versus 371 G’s for average commercial), but fractured along a print layer on impact. Had time allowed for printing of a helmet utilizing AREVOS’s true 3D printing technology with cross-hatched raster orientation, similarly printed test samples give strong evidence that this helmet would have reduced peak acceleration values and overall weight in comparison to similar commercial helmets, while avoiding fracture. This analysis exemplifies the significant capabilities and advantages of using true 3D printing methods where applications of traditional FDM printing would not suffice

A Personal Perspective on the Use of Modelling Simulation for Polymer Melt Processing

Copyright 2015 Carl Hanser Verlag. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Carl Hanser Verlag. The authors are grateful to the publisher, Carl Hanser Verlag, for letting the manuscript being archived in this Open Access repository. The final publication is available at = http://dx.doi.org/10.3139/217.3020International audienceThis paper gives a personal view on the state of art in relation to the modelling of polymer melt processing. The paper briefly reviews both industrial, laboratory and modelling developments over the last forty years and highlights the key aspects now required for realistic modelling of polymer melt processing. The paper summarizes elements relating to the numerical simulation of specific and general polymer processes and also provides topical examples of the application of numerical modelling to certain commercial processes. The paper concludes with identifying areas of polymer processing that still remain a challenge in relation to accurate prediction

Experimental investigation and process simulation of the compression molding process of Sheet Molding Compound (SMC) with local reinforcements

Die ganzheitliche virtuelle Auslegung von Faserverbundbauteilen aus Sheet Molding Compund (SMC) ermöglicht es durch die Berücksichtigung von Fertigungseffekten in der Struktursimulation, bedarfsgerechtere und somit leichtere und günstigere Bauteile zu fertigen. Hierfür muss jedoch die Prozesssimulation in der Lage sein, die SMC-spezifischen Blockströmung auf Grund der niedrig-viskosen Randschicht richtig zu beschreiben. Nur so kann das richtige Füllverhalten und somit auch die richtige Faserorientierungsverteilung vorhergesagt werden. Dies wird gerade im Kontext des zunehmenden Einsatzes von semi-strukturellen SMC-Formulierungen besonders wichtig. Darüber hinaus gibt es neue Konzepte der Hybridisierung von SMC mit lokalen unidirektionalen Verstärkungen, welche ebenfalls in der Prozesssimulation berücksichtigt werden müssen, um die Positionierung der Verstärkungen abzusichern. Aus diesem Grund wurde in dieser Arbeit ein neuer dreidimensionaler Ansatz für die Prozesssimulation von SMC entwickelt, der sowohl die durch Dehnviskosität dominierte Kernschicht, als auch die niedrig-viskose Randschicht berücksichtigt. Durch die Verwendung des gekoppelten Euler-Lagrange-Ansatzes, kann auch die Interaktion zwischen SMC und lokalen Verstärkungen abgebildet und vorhergesagt werden. Um die Informationen aus der Prozesssimulation in die Struktursimulation zu übertragen, wurde eine CAE-Kette weiterentwickelt, die das Übertragen der Information vom Prozess- zum Strukturnetz ermöglicht. Hierbei wird sowohl eine Cluster-Bildung, als auch eine Homogenisierung auf Basis der Faserorientierungsverteilung durchgeführt. Zur experimentellen Analyse des Fließverhaltens, sowie zur Bereitstellung der benötigten validen Materialparameter für die Prozesssimulation, wurde ein neues rheologisches Fließpresswerkzeug entwickelt. Mit diesem Werkzeug wurden erstmal das kompressible Verhalten von semi-strukturellen SMC Formulierungen nachgewiesen und über einen phänomenologischen Ansatz beschrieben. Auf Basis dieser Kompressibilitätsformulierung konnte ein neues rheologisches Model entwickelt, das eine genauere Charakterisierung ermöglicht. Durch die Charakterisierung von fünf unterschiedlichen SMC-Materialformulierungen, konnten einige Gesetzmäßigkeiten der Materialparameter abgeleitet werden

Experimental investigation and process simulation of the compression molding process of Sheet Molding Compound (SMC) with local reinforcements

In this book, a new three-dimensional approach for the process simulation of SMC is developed. This approach takes into account both, the core layer that is dominated by the extensional viscosity and the thin lubrication layer. In order to transfer the information from the process to the structure simulation, a CAE chain is further developed. In addition, a new rheological tool is developed to analyze flow behavior experimentally and to provide the required material parameters

A Path Planning Algorithm for a Dynamic Environment Based on Proper Generalized Decomposition

[EN] A necessity in the design of a path planning algorithm is to account for the environment. If the movement of the mobile robot is through a dynamic environment, the algorithm needs to include the main constraint: real-time collision avoidance. This kind of problem has been studied by different researchers suggesting different techniques to solve the problem of how to design a trajectory of a mobile robot avoiding collisions with dynamic obstacles. One of these algorithms is the artificial potential field (APF), proposed by O. Khatib in 1986, where a set of an artificial potential field is generated to attract the mobile robot to the goal and to repel the obstacles. This is one of the best options to obtain the trajectory of a mobile robot in real-time (RT). However, the main disadvantage is the presence of deadlocks. The mobile robot can be trapped in one of the local minima. In 1988, J.F. Canny suggested an alternative solution using harmonic functions satisfying the Laplace partial differential equation. When this article appeared, it was nearly impossible to apply this algorithm to RT applications. Years later a novel technique called proper generalized decomposition (PGD) appeared to solve partial differential equations, including parameters, the main appeal being that the solution is obtained once in life, including all the possible parameters. Our previous work, published in 2018, was the first approach to study the possibility of applying the PGD to designing a path planning alternative to the algorithms that nowadays exist. The target of this work is to improve our first approach while including dynamic obstacles as extra parameters.This research was funded by the GVA/2019/124 grant from Generalitat Valenciana and by the RTI2018-093521-B-C32 grant from the Ministerio de Ciencia, Innovacion y Universidades.Falcó, A.; Hilario, L.; Montés, N.; Mora, MC.; Nadal, E. (2020). A Path Planning Algorithm for a Dynamic Environment Based on Proper Generalized Decomposition. Mathematics. 8(12):1-11. https://doi.org/10.3390/math8122245S111812Gonzalez, D., Perez, J., Milanes, V., & Nashashibi, F. (2016). A Review of Motion Planning Techniques for Automated Vehicles. IEEE Transactions on Intelligent Transportation Systems, 17(4), 1135-1145. doi:10.1109/tits.2015.2498841Rimon, E., & Koditschek, D. E. (1992). Exact robot navigation using artificial potential functions. IEEE Transactions on Robotics and Automation, 8(5), 501-518. doi:10.1109/70.163777Khatib, O. (1986). Real-Time Obstacle Avoidance for Manipulators and Mobile Robots. The International Journal of Robotics Research, 5(1), 90-98. doi:10.1177/027836498600500106Kim, J.-O., & Khosla, P. K. (1992). Real-time obstacle avoidance using harmonic potential functions. IEEE Transactions on Robotics and Automation, 8(3), 338-349. doi:10.1109/70.143352Connolly, C. I., & Grupen, R. A. (1993). The applications of harmonic functions to robotics. Journal of Robotic Systems, 10(7), 931-946. doi:10.1002/rob.4620100704Garrido, S., Moreno, L., Blanco, D., & Martín Monar, F. (2009). Robotic Motion Using Harmonic Functions and Finite Elements. Journal of Intelligent and Robotic Systems, 59(1), 57-73. doi:10.1007/s10846-009-9381-3Bai, X., Yan, W., Cao, M., & Xue, D. (2019). Distributed multi‐vehicle task assignment in a time‐invariant drift field with obstacles. IET Control Theory & Applications, 13(17), 2886-2893. doi:10.1049/iet-cta.2018.6125Bai, X., Yan, W., Ge, S. S., & Cao, M. (2018). An integrated multi-population genetic algorithm for multi-vehicle task assignment in a drift field. Information Sciences, 453, 227-238. doi:10.1016/j.ins.2018.04.044Falcó, A., & Nouy, A. (2011). Proper generalized decomposition for nonlinear convex problems in tensor Banach spaces. Numerische Mathematik, 121(3), 503-530. doi:10.1007/s00211-011-0437-5Chinesta, F., Leygue, A., Bordeu, F., Aguado, J. V., Cueto, E., Gonzalez, D., … Huerta, A. (2013). PGD-Based Computational Vademecum for Efficient Design, Optimization and Control. Archives of Computational Methods in Engineering, 20(1), 31-59. doi:10.1007/s11831-013-9080-xFalcó, A., Montés, N., Chinesta, F., Hilario, L., & Mora, M. C. (2018). On the Existence of a Progressive Variational Vademecum based on the Proper Generalized Decomposition for a Class of Elliptic Parameterized Problems. Journal of Computational and Applied Mathematics, 330, 1093-1107. doi:10.1016/j.cam.2017.08.007Domenech, L., Falcó, A., García, V., & Sánchez, F. (2016). Towards a 2.5D geometric model in mold filling simulation. Journal of Computational and Applied Mathematics, 291, 183-196. doi:10.1016/j.cam.2015.02.043Falcó, A., & Nouy, A. (2011). A Proper Generalized Decomposition for the solution of elliptic problems in abstract form by using a functional Eckart–Young approach. Journal of Mathematical Analysis and Applications, 376(2), 469-480. doi:10.1016/j.jmaa.2010.12.003Falcó, A., & Hackbusch, W. (2012). On Minimal Subspaces in Tensor Representations. Foundations of Computational Mathematics, 12(6), 765-803. doi:10.1007/s10208-012-9136-6Canuto, C., & Urban, K. (2005). Adaptive Optimization of Convex Functionals in Banach Spaces. SIAM Journal on Numerical Analysis, 42(5), 2043-2075. doi:10.1137/s0036142903429730Ammar, A., Chinesta, F., & Falcó, A. (2010). On the Convergence of a Greedy Rank-One Update Algorithm for a Class of Linear Systems. Archives of Computational Methods in Engineering, 17(4), 473-486. doi:10.1007/s11831-010-9048-