Research

Fully Three-Dimensional Process Planning for Additive Manufacturing

Fully Three-Dimensional Process Planning for Additive Manufacturing

  Research by: Maxwell Micali While additive manufacturing and 3D printing have achieved notoriety for their abilities to manufacture complex three-dimensional parts, the state of the art is not truly three-dimensional. Rather, the process plans rely on a stack of discretized two-dimensional layers. Discretization of smooth, freeform features results in printed parts with stair-stepped surfaces, increasing the total volumetric error of the part and potentially diminishing the intended performance of functional surfaces. By performing process planning in a fully three-dimensional domain, as opposed to the 2.5D status quo, the capabilities of additive manufacturing are enhanced and the technologies can be more fully leveraged by designers and...

Read More

Particle method to simulate the flow through marine current turbines

Particle method to simulate the flow through marine current turbines

  Research by: David Fernandez-Gutierrez The Ocean represents a massive energy resource that can be employed for electricity generation. This fact has led to the growing interest ocean-driven energy generation over the last decade. This research project focuses on the development of a novel particle method to simulate the flow through marine current turbines. Ultimately, the goal of the project is to evaluate the probability and potential damage of collisions on the turbine blades from solid elements dragged by currents, and to optimize design modifications to mitigate such events. The proposed numerical method arises from the Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) philosophies, with emphasis placed on particle-infiltrated...

Read More

Non-invasive repair of piping systems

Non-invasive repair of piping systems

  Research by: Zeyad Zakey The use of piping systems is ubiquitous in several engineering applications, including process plants, factories, and oil refineries. Concerning the latter, it is of priority to maintain structural integrity of all systems to ensure constant operation. However, due to natural wear and tear, corrosion, or other else, piping systems may become damaged during use. In order to repair the system, it must be isolated. This entails stoppage of operation, resulting in loss of operating time and profit. The aim of this project was to propose an alternative method of repair. We hope to investigate a technique where solid particles are inserted into a pipe flow, while an external field is applied to guide the particles to a damage or target site. This is the first step. Secondly, as particles gather at the site, they will be fused in place via some other physical mechanism. Our study involved the first step of the process, accumulation of particles at the site. The problem setup consists of a fully developed laminar flow within a cylindrical pipe. Solid particles are inserted into the flow. The parameters of interest for the problem are the max flow velocity of the flow, the externally applied magnetic field strength, and the particle radii. The video above shows an example for a velocity of 5 m/s with a 1.5 Tesla magnetic field and a particle size of 200 microns. The video is part of a collaborative work done by Mukherjee et. al. (2013). As part of the paper, a non-dimensional scaling was done. Future work entails running the code with several parameter sets while seeing the relationship to a particle accumulation efficiency....

Read More

Multi-scale particle methods for improved heat transfer

Multi-scale particle methods for improved heat transfer

Syd Hashemi email: sydhashemi@berkeley.edu Research description Overview Although computer simulation power has astronomically increased since the beginning of the simulation by computers, and still is increasing, machine performance is still a limiting factor. This primarily restricts the size of the system that can be simulated, for example in the case of molecular dynamics the number of particles that can be handled with the computer, and the number of timesteps that can be calculated during the simulation is part of this restriction. Besides, to capture an important phenomena in the macro scale level, one needs much larger simulation time and extremely large number of particles, but in a conventional MD simulation, a great deal of computing time is used for uninteresting individual particle behavior. As a consequence, there still are problems for which a simulation turns out to be inefficient or even intractable. In this research, I study Dissipative Particle Dynamics (DPD), a method invented for carrying out particle based simulations of hydrodynamic behavior. I tried to use dissipative particle dynamics to address the problem of calculating heat transfer on some applications. In order to do that, the DPD method is used in order to calculate the heat transfer in small scales. Moreover in order to deal with larger scale flow situations a method is developed to couple different scales. Therefore, in combination to the small scale particle model, the continuum model is used to get the higher scale behavior of the flow. The Schematic of domain decomposition is presented in the following figure (top left) The domain decomposition over continuum model in an impinging jet is presented in the top right figure. In the bottom left a particle flow model video is shown for flow in a channel with turbulator and in the bottom right its continuum contour plot is presented http://cmrl.berkeley.edu/wp-content/uploads/part1.mp4 The particle code is used to solve heat transfer problem in some industrial simulation and the result is compared with experiment and CFD simulation. The left figure is heat transfer for flow in a channel with turbulators and right is the heat transfer over a...

Read More

Numerical Simulation of Laser Ablation of Diamond for Micro-machine Tooling

Numerical Simulation of Laser Ablation of Diamond for Micro-machine Tooling

  Research by: Marc Russell Micro-machining operations utilize micro-scale machine tools to carry out traditional manufacturing process (e.g. milling, drilling, etc. ) on microscale parts. They can be used for part creation as well as surfacing . Binder-less polycrystalline diamond (BPLCD) has been cited as an ideal machine tool material due to its superior mechanical properties (higher hardness, higher wear resistance, isotropic material properties, etc.) to that of the conventional diamond materials usually used for such tooling. However, because of these properties it is difficult to produce BPLCD tooling using traditional methodologies (grinding, etc.). In addition electrical discharge machining, often used for machining hard materials, cannot be used due to the non-conductance of BPLCD. Laser machining has been proposed as the ideal methodology for machining BPLCD. This work focused on using numerical simulation, in collaboration with experimental results, to predict the laser ablation of a BPLCD diamond material under a variety of lasering conditions to produce the sharpest and deepest ablation profile (ideal for machine tool creation). The use of femtosecond over nanosecond lasering was particularly investigated.Yoshinori Ogawa, Kazuo Nakamoto, Michiharu Ota, Tomohiro Fukaya, Marc Russell, Tarek I. Zohdi, Kazuo Yamazaki, Hideki Aoyama. A study on machining of binder-less polycrystalline diamond by femptosecond pulse laser for fabrication of micro-milling tools. CIRP Annals- Manufacturing Technology....

Read More

Numerical Simulation of Selective Laser Melting Process

Numerical Simulation of Selective Laser Melting Process

  Research by: Marc Russell Additive Manufacturing(AM), a.k.a. 3D printing, is a rapidly emerging technology that will revolutionize the manufacturing world by allowing for the production of net-shape, customizable, ready-to-use parts in a matter of hours. AM parts are built-up layer-by-layer from raw materials, under computer control in the image of a digital model. Selective Laser Melting of particle beds (SLM) is a particularly promising AM technique for producing complex 3D metallic structures through a repetitive process of deposition and guided laser melting of a bed of microscale, metallic particles. Subsequent layers are melted into previously deposited layers to produce 99.9% density parts with feature sizes of 200?m. Use of SLM parts however, currently requires a lengthy process of part qualification and certification to detect processing flaws including high residual stresses, porosity, and undesired microstructures. A better understanding of SLM is required to minimize these defects and allow for its full adoption by industry. Such an understanding can be achieved through numerical simulation of the process. Current numerical methods however have a high computational cost owing to the complexity of the physical processes involved in SLM. I propose to use mesh-free Particle Methods to simulate the thermal-mechanical fields and movement of the melt pool free surface to create an approximate, but expedient, numerical methodology to be used in efforts to understand and optimize the SLM process....

Read More

Particle Based Simulation Framework for Sintered Mechanical Components

Particle Based Simulation Framework for Sintered Mechanical Components

  Research by: Chang Yoon Park A Discrete Element Approach was used to create a framework for mechanical simulations of sintered materials. Bond stiffness between the particles were determined by performing eigenvalue analysis.
If the stored energy in the bonds exceeds the pre-determined fracture surface energy, the bonds were deactivated to simulate fracture. A 3 Point Bending test was performed as an...

Read More

Computational Multi-Phase Materials Design

Computational Multi-Phase Materials Design

Research by: Santiago Miret Ceramic Matrix Composite (CMC) materials are becoming more and more important for high temperature and high stress environments, such as those found in aerospace and automotive applications. The aim of this project is to create a design tool for CMCs using numerical methods to compute the effective properties of the materials and to simulate their behavior in high stress...

Read More

Holographic Diffractive Optics for Stereolithography

Holographic Diffractive Optics for Stereolithography

  Research by: Brett Kelly Existing additive manufacturing techniques tend to operate by printing of two-dimensional cross-sections layered on top of one another to form a three dimensional geometry. Optical printing techniques such as photopolymerization by stereolithography have the potential to move towards “true” 3D printing through the use of holographic light shaping. By controlling the phase of an incident coherent wave front there is potential to pattern light in 3 dimensions and cure non-planar geometries in a single exposure. This offers the advantages of increased print speed, the potential to avoid anisotropies induced by layered printing, and the potential to cure 3D volumes in situ. This research is focused on the use of diffractive optical elements, both in the form of electrically-addressed spatial light modulators and nanoimprinted surface relief patterns, to cure photopolymer resins and hydrogels into 3D geometries. To aid in the design of experiments, optical and chemical models have been developed to predict degree of crosslinking spatially throughout a polymerizing 3D volume. Models include those for optical propagation and diffraction as well as chemical species reaction and diffusion. This research aims to apply these printing processes to biological applications such as scaffold fabrication for tissue...

Read More

Modeling and simulation of the multi-jet printing process

  Research by: Shanna Tune Additive Manufacturing (AM), more commonly known as 3D printing, is the process of building up material layers to produce a final product capable of having freeform geometries and internal structures. Most AM processes utilize polymer and plastic materials which have limited applications due to the anisotropic material response resulting from the layer-by-layer construction and generally poor fine feature resolution. One polymer based process, the material jetting process, or Multi-Jet Printing (MJP), has a potential for increased use as the technique is capable of producing high quality polymer components with resolutions of 100 microns. MJP achieves the fine resolution through the selective deposition of UV light curable photopolymer and support wax from a series of printer heads. One of the challenges associated with this AM technique is that residual stresses can form within the material from over curing resulting in part deformation. This project focuses on the development of a computational model able to capture the MJP process so to understand material response during...

Read More

Computational research on self-assembly in a micro/nano scale

  Research by: Dong Hoon Kim Although the demand for miniaturized products is increasing these days, existing manufacturing robots in serial production systems seem to have difficulties in producing miniature products because they have had to become increasingly larger to properly complete precise machining. Therefore, small-scale self-assembly could provide economic and efficient solutions to overcome this limitation. Also, the self-assembly of 3D structures at the micro scale could make it possible to fabricate new materials. The characteristics of different materials could be combined to produce advanced engineering materials including smart meta-materials with new possibilities. The experimental research would be preceded to conduct research on self-assembly. Also, the lessons learned from the experimental macroscopic research could be extrapolated to the micro/nano domain. However, since the behavior of the self-assembly particles at a micro/nano scale could differ greatly from that of the macroscopic scale, the use of a numerical method to solve partial differential equations and the application of Discrete Element Method is necessary to properly analyze and interpret the behavior of small scale particles in various external conditions. To deeply understand the mechanism of crystallization processes of micro/nano particles, we have to take advantage of particle-based computational methods to simulate microstructural behavior and compare it with the results of experimental work. On the basis of the application of computational methods, the perspective to the self-assembly could be expanded to the various methods including magnetic, fluidic, electrochemical, and electrostatic...

Read More

Modeling and simulation of functionalized materials for 3-D printing

Modeling and simulation of functionalized materials for 3-D printing

  Research by: Erden Yildizdag 3-D printing also known as additive manufacturing has an increasing demand in the industry to manufacture different kinds of devices. Thus, materials used for 3-D printing need to have different properties (electrical, magnetic, thermal, mechanical, etc.) depending on what we are manufacturing. The aim of this project is modeling new functionalized materials and look for their performances with numerical and experimental studies. Firstly, overall response of the new functionalized material is investigated using multi-scale computational homogenization techniques as numerical tool. After that, different materials are mixed into extruder that we have in our lab to manufacture filaments for 3-D printer. Then, samples printed with new composite material are tested (tensile test, thermal and electrical conductivity tests, etc.) and their performances are compared with numerical...

Read More

Beam Based Modeling of Open-Celled Foams

Beam Based Modeling of Open-Celled Foams

Research by: Matthew Kurry With modern polymer and composite technology helmets used by military personnel have become so good at preventing death from kinetic impacts that soldiers are surviving attacks that would have killed them before. While more soldiers are surviving, the momentum transfer due to the impact can injure the wearer’s brain. In this research we seek to understand the momentum and energy transfer physics of open-celled foams to better protect helmet wearers. Various projects in this research include the processing of scanned foam images and the used of beam finite elements to simulate impact events in open cells....

Read More

Modeling and simulation of particle doped materials under an electromagnetic field

Modeling and simulation of particle doped materials under an electromagnetic field

Bhavesh Patel email: b.patel@berkeley.edu Research description Overview The interests of this research are particle doped composites materials, made by adding particles into a base material commonly called matrix material. The focus is on potential application for micro electromagnetic devices such as magnetic cores for planar inductor or nano composite capacitors. Based on these applications, the objective is to propose a numerical tool that allows simulating behavior of micro/nano particle doped material under an electromagnetic (EM) field. Specifically, knowing the external EM field the composite is immersed in, we want: • The state of the EM field inside the material • The variation in temperature via Joule heating • The value of its effective magnetic permeability μ* and the effective electric permittivity ε* Some simulations and results Evolution of electric field intensity E, magnetic field intensity H and temperature over a randomly generated representative volume element (RVE) of a test material is computed by simultaneously solving dynamic Maxwell’s equations using Yee’s scheme and heat equation using Forward Euler scheme. Below are some sample simulations. RVE http://cmrl.berkeley.edu/wp-content/uploads/Bhavesh_Ex_field.mp4 Ex field over a cross-section http://cmrl.berkeley.edu/wp-content/uploads/Bhavesh_Hx_field.mp4 Hx field over a cross-section http://cmrl.berkeley.edu/wp-content/uploads/Bhavesh_temp.mp4 Temperature over a cross-section The effective EM properties of interest are computed directly from the internal EM fields. Validity of the results is checked using known analytical...

Read More

Soil Simulations in Subterranean Blasts

Soil Simulations in Subterranean Blasts

Research by: Matthew Kury Underground blasts are of particular interests to civilian miners as well as military defense contractors. Soils are complicated composite of grains, fluids and other materials, which are often blown out during explosions. The complicated nature of the event requires a multi-method approach in order to capture the physics of the event and to make simulating the event possible. I am developing a parallel discrete element code to capture the behavior of the soil near the blast event and a finite element code to represent the behavior of the soil further away from the blast center. Watch the...

Read More

Energy Efficient Facades for Buildings

Energy Efficient Facades for Buildings

Research by: Aashish Ahuja Lighting consumes a substantial amount of energy in buildings that has made it imperative to depend more on daylighting.                                                    My research tries to computationally assess the qualities of a novel light-channeling facade subsystem called ‘Translucent Concrete’ (TC).   I conduct various simulations on my model, starting with: 1) Ray Tracing to estimate the performance of the TC system during the day.   2) Heat transmission analysis to calculate the thermal performance of TC and avenues for improvement.   3) Exploring nonimaging concentrator technology to supplement the TC subsystem.   Publications: Ahuja, A., Casquero-Modrego, N. and Mosalam, K.M. “Evaluation of Translucent Concrete using ETTV-based approach”, International Conference on Building Energy Efficiency and Sustainable Technologies (ICBEST), 31st Aug – 1st Sep 2015, Singapore Ahuja, A., Mosalam, K.M. and Zohdi, T.I. “An Illumination Model For Translucent Concrete Using RADIANCE”, 14th International Conference of the International Building Performance Simulation Association (IBPSA), 7th-9th Dec 2015, Hyderabad, India. Ahuja, A., Mosalam, K.M. and Zohdi [2014], “Computational Modeling of Transclucent Concrete Panels,” ASCE, Journal of Architectural Engineering. Mosalam, K.M., N. Casquero-Modrego, J. Armengou, A. Ahuja, T.I. Zohdi and B. Huang, “Anidolic Day-Light Concentrator in Structural Building Envelope,” First Annual International Conference on Architecture and Civil Engineering (ACE 2013), 18-19 March 2013, Singapore. Patent: Mosalam, K.M., Casquero-Modrego, N., Ahuja, Aashish, Huang, Baofeng “BRIGHT: Building With Radiant And Insulated Green Harvesting Technology”, Tech ID: 25071 / UC Case 2015-159-0, Fun Stuff: Construction of TC...

Read More

Operational Analysis of Artificial Photosynthetic Systems

Operational Analysis of Artificial Photosynthetic Systems

  Research by: John Stevens I build computational models to predict the net fuel energy harvest by and light transmission through multiphase wireless photoelectrochemical systems that use optical concentration. With these models, I assess optimal designs to accommodate different solar tracking methodologies, photovoltaic cells, catalysts, deployment locations, optical concentration ratios and cell geometries. This allows me to propose designs to reduce energy costs, primary energy inputs and efficiency losses, while enhancing device lifetime. Additionally, I use computational models and experimental processes to study the effects of heat transfer on photoelectrochemical systems that use liquid and gaseous reactants. Publications: Sathre, R.; Scown, C. D.; Morrow, W. R.; Stevens, J. C.; Sharp, I. D.; Ager, J. W. III; Walczak, K. A.; Houle, F. A.; Greenblatt, J. B. “Life-cycle Net Energy Assessment of Large-Scale Hydrogen Production Via Photo-Electrochemical Water Splitting” Energy Environ. Sci. 2014, 7, 3264-3278. Singh, M. R.; Stevens, J. C.; Weber, A. Z. “Design of Membrane-Encapsulated Wireless Photoelectrochemical Cells for Hydrogen Production” J. Electrochem. Soc. 2014, 161,...

Read More

Thermal Barrier Coatings

Thermal Barrier Coatings

Research by: Peter Minor To protect against high temperatures, gas turbines use highly porous ceramic thermal barrier coatings (TBCs) which are susceptible to erosion and foreign object impact damage. Few numerical tools exist which are capable of both accurately capturing the specific failure mechanisms inherent to TBCs and iterating design parameters without the requirement for coupled experimental data. To overcome these limitations, I’m developing a discrete element model (DEM) to simulate the microstructure of a TBC using a large-scale assembly of bonded particles. The particles can be combined to create accurate representations of TBC geometry and porosity. The inclusion of collision-driven particle dynamics and bonds derived from displacement-dependent force functions endow the microstructure model with the ability to deform and reproduce damage in a highly physical manner. Typical TBC damage mechanisms such as compaction, fracture and spallation occur automatically, without having to tune the model based on experimental observation. Therefore, the first order performance of novel TBC designs and materials can be determined numerically, greatly decreasing the cost of development. To verify the utility and effectiveness of the proposed damage model framework, a nanoindentation materials test simulation was developed to serve as a test case. A good correlation was found between the predicted properties calculated by the model and those found through experimental nanoindentation tests. Furthermore, conforming to the benefits of DEM, the model was able to accurately recreate the same material damage characteristics observed in literature, such as the onset of inelastic deformation from fracture and creep. Watch the...

Read More

Electromagnetically Sensitive Ballistic Fabric

Electromagnetically Sensitive Ballistic Fabric

Research by: Alejandro Queiruga High strength textiles are a fundamental component of armors in multiple applications, where they are coupled with metal and ceramic plates and various other systems. In this research, the effect of applying electromagnetic fields to a ballistic fabric undergoing impact is explored, wherein an external magnetic field induces deformation in an electrified sheet to influence the behavior of the projectile. The interaction between the applied electromagnetic fields and the resulting range of forces that can be applied onto the moving projectile is modeled by simplified analytical relations to inform the design space. A computational model used to simulate the dynamic system of the projectile and a layered ballistic fabric with coupled electromagnetic, mechanical, and contact physics. A single sheet of the ballistic fabric is modeled as a lattice of lumped masses interconnected by yarn segments. The electromagnetic properties of the fabric are modeled by solving an electrical network model on the lattice. A rigid-body projectile model is coupled to the fabric model that can handle arbitrary surface geometries. The interaction between layers of fabric sheets is incorporated through a nodally based contact model. The effect of altering the geometry of the projectile as well as the number of sheets used in the armor is explored through the model. Watch the...

Read More

Multiphysical Modeling and Simulation of Selective Laser Sintering

Multiphysical Modeling and Simulation of Selective Laser Sintering

Research by: Rishi Ganeriwala Additive manufacturing refers to a relatively recent group of manufacturing technologies whereby one can “3D print” parts, which has the potential to significantly reduce waste and alter the entire industry. Selective laser sintering/ melting (SLS/ SLM) is one type of additive manufacturing technology with the distinct advantage of being able to 3D print metals. In SLS/ SLM parts are built up layer-by-layer out of powder particles, which are selectively melted via a laser. However, in order to produce defect free parts of sufficient strength, the process parameters (laser power, scan speed, layer thickness, etc.) must be carefully optimized. Obviously, these process parameters will vary depending on material, part geometry, and desired final part characteristics. Thus, the aim of this research is to produce a multiphysical, computational model of SLS/ SLM so that the process parameters can be quickly optimized without the need for running numerous costly, and energy intensive experiments. Click on the following links for videos of the simulation. Videos: Deposition and subsequent laser heating of a layer of metal, powder particles using the discrete element method (DEM). Each individual particle is assumed to be spherical in shape and to have a homogenous temperature. Single pass of a laser beam over a pre-deposited layer of steel powder particles. In this simulation DEM particles are placed on top of the solid, underneath substrate, which is modeled via the finite difference method (FDM). Particles colored red indicate that they have melted, and side view of the same simulation. Notice how part of the underneath substrate layer is also melted (in addition to the particles). This is desirable to ensure proper bonding between layers during the SLS/ SLM...

Read More

Flowing particulate media

Flowing particulate media

Flowing particulate media are ubiquitous in a wide spectrum of applications that include transport systems, fluidized beds, manufacturing and materials processing technologies, energy conversion and propulsion technologies, sprays, jets, slurry flows, and biological flows.

Read More

Colliding and Flowing Particles

Colliding and Flowing Particles

Flowing particulate media are ubiquitous in a wide spectrum of applications that include transport systems, fluidized beds, manufacturing and materials processing technologies, energy conversion and propulsion technologies, sprays, jets, slurry flows, and biological flows. The discrete nature of the media, along with their underlying coupled multi-physical interactions can lead to a variety of interesting phenomena, many of which are unique to such media. My research explores the utility of numerical simulations based on the discrete element method and collision driven particle dynamics methods for analyzing flowing particulate media. I have developed a FORTRAN based software library for discrete particle simulations, and used it to analyze the flow of an erosive stream of particles impacting a target surface, and the flow and deposition of particulate sprays. Currently, I am working on extending the discrete particle calculations to two-way coupled fluid-particle interaction problems. Watch the...

Read More

Ablation

Ablation

  Roll-to-roll manufacturing has the potential to be a high throughput and low cost technique for producing flexible electronics. Currently, however the inability to control the flow of the inks precisely prevents the creation of the sharp and small features needed to produce electronics. In my research, I am using the Discrete Element Method (DEM) to explore the whether laser ablation can be used to improve the properties of the printed features. A general DEM simulation environment has been written allowing for multiple element types each with distinct properties and interactions relations. To model ablation, particles that reach their evaporation temperature loss mass in accordance with heat input and their heat of vaporization which results in a decrease in radius of the element. If the elements exhibit attract behaviour this can have the result of drawing in surrounding elements. With this simulation framework, we are examining if with different shaped heat sources, intensities and ligand properties it is possible to create different geometries of self assembled nano-particles. Watch the video…...

Read More