118 research outputs found
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Parametric Based Controller for Rapid Prototyping Applications
A methodology aiming at reproducing in Rapid Prototyping applications, exact parametric
curves from CAD data is presented. The approach consists of converting the space-based parametric
curves from the CAD system into time-base, such that the equations of the curve in terms of time are
then fed to a controller directly. Optimization is used to solve the problem, which has both Rapid
Prototyping process and scanning constraints. With information such as the equation of the curve, its
first and second derivatives with respect to time, a real-time trajectory controller can be designed.
The trajectory displays an increase in accuracy over traditional approaches using STL files, which is
ofthe order of the chordal tolerance used to generate tessellations. The system model involves
electrical and mechanical dynamics of the galvanometers and sensors. The controller, which acts on
two mirrors, deflecting the laser beam of a stereolithography machine in the x and y directions
respectively, should be easily substituted for current systems. Application of the methodology to
freeform curves shows acceptable tracking and can be improved by judicious selection ofthe equation
representing the spatial parameter as a function of time.Mechanical Engineerin
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Planning the Process Parameters During Direct Metal Deposition of Functionally Graded Thin-Walled Parts Based on a 2D Model
The need for functionally graded material (FGM) parts has surfaced with the development
of material science and additive manufacturing techniques. Direct Metal Deposition (DMD)
processes can locally deposit different metallic powders to produce FGM parts. Yet inappropriate
mixing of materials without considering the influence of varying dilution rates and the variation
of material properties can result in inaccurate material composition ratios when compared to the
desired or computed compositions. Within such a context, this paper proposes a 2D simulation
based design method for planning the process parameters in the DMD manufacturing of designed
thin-walled parts. The proposed scheme is illustrated through two case studies, one of which is a
part with one-dimensional varying composition and the other with two dimensional variation.
Using the proposed method, the process parameters can be planned prior to the manufacturing
process, and the material distribution deviation from the desired one can be reduced.Mechanical Engineerin
AMGA: an archive-based micro genetic algorithm for multi-objective optimization
In this paper, we propose a new evolutionary algorithm for multi-objective optimization. The proposed algorithm benefits from the existing literature and borrows several concepts from existing multi-objective optimization algorithms. The proposed algorithm employs a new kind of selection procedure which benefits from the search history of the algorithm and attempts to minimize the number of function evaluations required to achieve the desired convergence. The proposed algorithm works with a very small population size and maintains an archive of best and diverse solutions obtained so as to report a large number of non-dominated solutions at the end of the simulation. Improved formulation for some of the existing diversity preservation techniques is also proposed. Certain implementation aspects that facilitate better performance of the algorithm are discussed. Comprehensive benchmarking and comparison of the proposed algorithm with some of the state-of-the-art multi-objective evolutionary algorithms demonstrate the improved search capability of the proposed algorithm
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Performance of Stainless Steel AlSi 304 Wire Reinforced Metal Matrix Composites Made Using Ultrasonic Additive Manufacturing in Bending
Ultrasonic additive manufacturing (UAM) is a solid-state additive and subtractive
manufacturing process that utilizes ultrasonic energy to produce layered metallic parts.
The process is easily extended to create advanced multi-material structures, e.g., metal
matrix composites, functionally graded metallic components, and shape memory alloys.
This research utilizes a three point bending test to compare the elastic modulus in metal
matrix composites (MMC’s) specimens consisting of stainless steel wire reinforcements
with an aluminum matrix to unreinforced test specimens; both specimens are produced by
UAM. In the MMC the volume fraction of wire is relatively low, 0.77%, yet yields an
average increase in modulus of 8.9%.Mechanical Engineerin
Energy Based Functional Decomposition in Preliminary Design
The authors wish to thank Dr. Jonathan Maier, Dr. Gregory Mocko and Mr. Benjamin Caldwell for their valuable comments on the draft of the paper.This paper presents an energy based approach to functional decomposition that is applicable to the top down design (system to subsystems to components) of mechanical systems. The paper shows that the main functions of convert and transmit are sufficient to focus on the “functional flow” or main energy flow resulting in the specific action sought as a result of the artifact being designed, and can be expanded upon at the lowest level when looking for specific solutions based upon the energy and mass balances and the knowledge within the design team. This approach considers function as a transformation and also fits the approach presented in TRIZ. The standard energy, material, and signal flows are seen as forms of energy flows, and it is only their transformation and transmission that is sought. This simplified approach, coupled with an aspect of control and interaction between a reference state and the artifact or between various components is sufficient to comprehensively describe the system that matches very nicely the value function approach of Miles. Furthermore, as these interactions can be considered as artifactartifact affordances when considering the artifact for either artifact interaction or within an environment, its relation to the user and to the reference state can be addressed during the design phase, in addition to the functions
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The Clemson Intelligent Design Environment For Stereolithography-Cides 2.0
There are a large number of commercial Rapid Prototyping (RP) devices available today. All
ofthese machines begin with a Computer-Aided Design (CAD) model, which is tessellated,
sliced and then built layer-by-Iayer on the RP device. All ofthese operations, except the actual
building ofthe part, are completed on a computer. Therefore, many improvements to the RP
processes can be achieved through software, without affecting the RP devices or the warranties
on them. This has led to the development of a front-end software product to support the task of
preparing the part to be built. The Clemson Intelligent Design Environment for
Stereolithography (CIDES) is a user-centered interface between the CAD system and RP
systems, primarily the Stereolithography Apparatus (SLA).
CIDES 2.0 is designed to provide a variety oftools which are valuable to the users ofRP
systems, including the ability to view and modify tessellated (STL) files, generate supports, and
slice STL files into layer (SLI) files for use on an SLA. It also provides the ability to view SLI
and merged (V) files. Furthermore, CIDES offers additional translation capabilities that make it
valuable for other RP processes. The package has proven useful in the Laboratory to Advance
Industrial Prototyping (LAIP) at Clemson University. CIDES 2.0 is a new X Windows-based
release based on the original version ofCIDES with many additional features. A new HumanComputer
Interface is the major improvement to this release.Mechanical Engineerin
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Examination of Build Height in Ultrasonic Consolidation for Foil Width Specimens Using Supports
Ultrasonic consolidation (UC) is a novel, solid-state, additive manufacturing
fabrication process. It consists of ultrasonic joining of thin metal foils and contour milling
to directly produce functional components in a variety of geometries. The bond between
layers forms when an ultrasonic horn creates a local oscillating stress field at the mating
surfaces. It is commonly theorized that the high frequency vibration under pressure
produces a metallurgical bond without melting the base material. The mechanism behind
the bond is believed to be due to interfacial motion and friction that disrupts surface
contaminants, arguably allowing direct metal to metal contact, and producing sufficient
stress to induce plastic flow and promote the growth of grains across the mating surfaces.
Ignored in this explanation is the role of substrate dimensions on the quality and strength
of the joining process. Researchers have previously examined the effective height
limitations of the build process, i.e., the limiting height to width ratio of one of the
component features being fabricated. This paper extends the experimental work on using
support materials to extend build height on specimens using two different candidate materials, tin bismuth, and a mixture of sugar, corn syrup, and water, referred to as
“candy”. Tin bismuth and candy the represent the extremes of a tradeoff between
convenience and stiffness that a support material must possess.Mechanical Engineerin
Metronidazole pharmacokinetics in geese (Anser anser domesticus) after intravenous and oral administrations
Metronidazole (MTZ) is a 5-nitroimidazole anti-bacterial and anti-protozoal drug. In human and companion animal medicine, MTZ remains widely used due to its effectiveness against anaerobic bacteria and protozoa. In farm animals, however, MTZ is currently prohibited in several countries due to insufficient data on nitroimidazoles. The purpose of this study was to assess its pharmacokinetics (PK) in geese after single intravenous (IV) and oral (PO) administrations. Fifteen-month old healthy male geese (n = 8) were used. Geese were subjected to a two-phase, single-dose (10 mg/kg IV, 50 mg/kg PO), open, longitudinal study design with a two-week washout period between the IV and PO phases. Blood was drawn from the left wing vein to heparinized tubes at 0, 0.085 (for IV only), 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, 24, and 48 h. Plasma MTZ concentrations were measured using HPLC coupled to an UV detector, and the data were pharmacokinetically analyzed using PKanalix (TM) software with a non-compartmental approach. MTZ was still quantifiable and well above the LLOQ at 24 h after both routes of administration. Following IV administration, terminal elimination half-life, volume of distribution, and total clearance were 5.47 h, 767 mL/kg, and 96 mL/h/kg, respectively. For the PO route, the bioavailability was high (85%), and the mean peak plasma concentration was 60.27 mu g/mL at 1 h. When parameters were normalized for the dose, there were no statistically significant differences for any of the PK parameters between the two routes of administration. The study shows that oral administration of MTZ seems to be promising in geese, although comprehensive research on its pharmacodynamics and multiple-dose studies are necessary before its adoption in geese can be further considered
Honeycomb Structures for High Shear Flexure
The present invention provides an improved shear band for use in non-pneumatic tires, pneumatic tires, and other technologies. The improved shear band is uniquely constructed of honeycomb shaped units that can replace the elastomeric continuum materials such as natural or synthetic rubber or polyurethane that are typically used. In particular, honeycomb structures made of high modulus materials such as metals or polycarbonates are used that provide the desired shear strains and shear modulus when subjected to stress. When used in tire construction, improvements in rolling resistance can be obtained because of less mass being deformed and reduced hysteresis provided by these materials. The resulting mass of the shear band is greatly reduced if using low density materials. Higher density materials can be used (such as metals) without increasing mass while utilizing their characteristic low energy loss
The Component Packaging Problem: A Vehicle for the Development of Multidisciplinary Design and Analysis Methodologies
This report summarizes academic research which has resulted in an increased appreciation for multidisciplinary efforts among our students, colleagues and administrators. It has also generated a number of research ideas that emerged from the interaction between disciplines. Overall, 17 undergraduate students and 16 graduate students benefited directly from the NASA grant: an additional 11 graduate students were impacted and participated without financial support from NASA. The work resulted in 16 theses (with 7 to be completed in the near future), 67 papers or reports mostly published in 8 journals and/or presented at various conferences (a total of 83 papers, presentations and reports published based on NASA inspired or supported work). In addition, the faculty and students presented related work at many meetings, and continuing work has been proposed to NSF, the Army, Industry and other state and federal institutions to continue efforts in the direction of multidisciplinary and recently multi-objective design and analysis. The specific problem addressed is component packing which was solved as a multi-objective problem using iterative genetic algorithms and decomposition. Further testing and refinement of the methodology developed is presently under investigation. Teaming issues research and classes resulted in the publication of a web site, (http://design.eng.clemson.edu/psych4991) which provides pointers and techniques to interested parties. Specific advantages of using iterative genetic algorithms, hurdles faced and resolved, and institutional difficulties associated with multi-discipline teaming are described in some detail
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