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...

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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...

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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....

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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...

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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....

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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....

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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...

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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...

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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...

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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...

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