93 research outputs found
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Using Literature Reviews as a Learning Tool for Solid Freeform Fabrication
Over the past six years, students involved in the “Non-Traditional & Additive Manufacturing”
course at Utah State University have been assigned an in-depth literature review as one their
course projects. This literature review, done in groups of 2 or 3 students, involves becoming an
expert on a topic of interest to the students and then presenting this material to the class as an indepth, oral presentation in addition to writing a journal-like review article on the topic. This
project has proved to be a consistently effective method for enhancing learning of SFF
technologies and their applications, and has been consistently noted by students in their course
evaluations as a highly effective teaching tool. The methodology used for assigning and
assessing these projects will be explored, in addition to a discussion of the benefits of this project
toward meeting ABET criteria for accreditation of engineering programs.Mechanical Engineerin
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Development of a Co-Cr-Mo to Tantalum Transition using LENS for Orthopedic Applications
Biomedical implant material research using additive manufacturing is a popular field of
study. Many potential material combinations exist which, if implemented properly, could
have a significantly positive effect on implant life and functionality. One material
combination of interest is attaching porous Ta bone ingrowth material to a CoCrMo
corrosion and wear resistant bearing surface. An investigation of the ability of the LENS
process to join Ta to CoCrMo was undertaken. Direct joining of CoCrMo to Ta was
known to be problematic, and thus transitional layers of other biomedically-compatible
materials were investigated. It was determined that a transitional layer of zirconium
appeared to be the best transitional material for this application due to its excellent
biocompatibility, followed by stainless steel, with a lesser biocompatibility but better
adhesive properties.Mechanical Engineerin
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A Motion Planning Approach for Fabrication of Complex 3-D Shapes in a LENS� Process
This paper discusses an approach for planning the motion of the laser deposition
head relative to the part for fabrication of complex 3-D shapes such as parts with
overhangs, branches, and internal cavities in direct metal deposition processes such as the
LENS‘ process. The proposed approach is based on slicing the solid model of the part
into equal-thickness slices perpendicular to the normal build direction and formulating a
motion planning strategy based on the properties of these slices. The paper discusses the
four sub-approaches that are proposed to handle a variety of complex 3-D shapes parts.Mechanical Engineerin
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An Integrated Approach to Finish Machining of RP Parts
An integrated approach to finish machining of RP parts and tools has been
developed at the University of Rhode Island. Pre-processing operations, including surface
offsets to add machining stock, and post-processing operations, including CNC tool-path
generation, have been combined into one integrated set of software algorithms to make
possible the effective finishing of near-net parts and tools from RP. An in-depth
description of the uniquely developed STL vertex offset algorithm will be explored as
well as an automatic method for adaptive raster milling, sharp edge contour machining
and hole drilling from STL files. The time involved and surface finish benefits of the
developed methodology will be compared to alternative approaches.Mechanical Engineerin
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STL-based Finish Machining of Rapid Manufacturing Parts and Tools
Accuracy and surface quality problems when utilizing layered manufacturing
technologies have limited its use in tooling areas. Therefore, in some situations a CNC
machine is still necessary for finish machining of rapid manufactured parts and tools.
This paper presents a STL-based CNC machining technique for automating the finishing
of RP tools and parts to obtain CNC accuracies and surface finishes. Preprocess
operations, such as rotate and scale, are used to change the part orientation and
compensate for shrinkage in the whole process. An offset algorithm is developed to add
“skin” to the original STL file to make sure enough material is left for finish machining
after the rapid manufacturing process. The machining strategy of adaptive raster milling
of the surface, plus hole drilling and sharp edge contour machining, is proposed to finish
the RP parts and tools. Corresponding algorithms of adaptive tool path generation for
raster milling, automatic hole recognition and drilling tool path generation, and automatic
sharp edge detection and tool path generation are developed. Finally, a designed
benchmark is machined successfully by using the above mentioned machining strategies
and tool paths generated by developed software.Mechanical Engineerin
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Time Homogenization of Al3003 H-18 Foils Undergoing Metallurgical Bonding Using Ultrasonic Consolidation
A dislocation density based finite element model was formulated and initially validated
using published experimental data for simple shear deformation of a single crystal pure
aluminum and uniaxial tension of bulk polycrystalline Al 3003-H18 alloy. The model was
extended to predict the deformation behavior of 150µm Al 3003-H18 foils undergoing ultrasonic
consolidation (UC). The simulated results were in good agreement with the experimental results
for the evolution of linear weld density and embrittlement due to grain substructure formation. A
novel time homogenization approach has been further formulated which significantly reduces the
computational overhead. The time-homogenization approach uses the Almost Periodic Time
Homogenization (APTH) operator based on an asymptotic Forward-Euler scheme for integrating
the coarse time increments. The computational efficiency is proportional to the ratio of coarse to
fine time scales.Mechanical Engineerin
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Structurally Embedded Electrical Systems Using Ultrasonic Consolidation (UC)
Current research has demonstrated the use of Ultrasonic Consolidation (UC) to embed
several USB-based sensors into aluminum, and is working toward embedding suites of
sensors, heaters and other devices, connected via USB hubs, which can be monitored and
controlled using an embedded USB capable processor. Additionally, the research has
shown that electronics can be embedded at room temperature, but with some inter-layer
delamination between the ultrasonically bonded aluminum layers. Embedding sensors
and electronics at 300o
F to overcome the delamination issues resulted in optimal
bonding, and the sensors used thus far have functioned normally. Future investigation
will explore other UC parameter combinations to ascertain the quality of embedding at
lower temperatures.Mechanical Engineerin
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An Investigation of LENS®-Deposited Medical-Grade CoCrMo Alloys
A series of deposition experiments using CoCrMo were performed using an Optomec
LENS®1
machine. An analysis of hardness, microstructure, and wear trends of the deposited
alloys was undertaken in an attempt to determine the applicability of using LENS® to create
better materials for orthopedic implants. It was found that LENS®-deposited CoCrMo alloys
were harder than wrought materials, however initial wear tests indicated that LENS®-deposited
alloys were less resistant to abrasive wear than wrought alloys.Mechanical Engineerin
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A New Finite Element Solver using Numerical Eigen Modes for Fast Simulation of Additive Manufacturing Processes
A new efficient numerical technique has been formulated for dimensional reduction and phenomenological
multi-scale simulation of additive manufacturing processes using finite element analysis. This technique is
demonstrated using prismatic build volumes to represent the Selective Laser Melting powder bed fusion additive
manufacturing process. The Eigen modes determined as an outcome of implementation of this technique will
help to reduce the time necessary for optimization of process parameters and closed loop control. In addition to
thermal simulations of the Selective Laser Melting process, this technique is also applicable to the simulation of
lattice structures, layered materials such as ultrasonically consolidated laminates, thin walled coatings and
development of high fidelity beam and plate theories for parts made using additive manufacturing processes. A
future integration of this method with analytical Eigen wavelets will provide infinite support compared to finite
support provided by directional polynomial shape functions currently used for implementation of finite element
strategies. The present Eigen modes will be also useful in analysis and optimization of mask projection based
additive manufacturing processes.Mechanical Engineerin
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An Energy Dissipative Constitutive Model for Multi-Surface Interfaces at Weld Defect Sites in Ultrasonic Consolidation
A new finite element based constitutive model has been developed for quantification of energy
dissipation due to friction and plastic deformation at the mating interface of two surfaces during
the Ultrasonic Consolidation process. This work will include bridging the mesoscopic response of
a dislocation density based crystal plasticity finite element framework at inter and intra-granular
scales and a point at the macroscopic scale. This response will be used to develop an energy
dissipative constitutive model for multi-surface interfaces at the macroscopic scale. The
constitutive model will be used for quantification of energy consumed at lack of fusion and trapped
oxide defects present in the build and the amount of energy input required to compensate for it.
This numerical procedure will help in real time optimization of process parameters and closed loop
control.Mechanical Engineerin
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