15 research outputs found
In Vitro Immersion Behavior of Cold Sprayed Hydroxyapatite/Titanium Composite Coatings
In previous study, dense and homogenous 20wt% HAP/Ti composite coatings were successfully deposited on Ti substrates by cold gas dynamic spray technique. The results revealed that the phase composition of the HAP in the deposit is identical to that of the precursor powder and the bonding strength of the deposit is comparable/better to that of the plasma sprayed HAP. A relatively higher corrosion current of HAP/Ti composite than that of pure Ti coating in simulated body fluid indicates a good bioactivity for composite coating. In the present study, in vitro immersion test is carried out for various period of time and the formation of apatite layer on surface of composite coating proves the good bioactivity of the composite coating further. The cold sprayed HAP/Ti composite can be anticipated to be a promising load-bearing implant material for biomedical applications
Data mining algorithm for manufacturing process control
In this paper, a new data mining algorithm based on the rough sets theory is presented for manufacturing process control. The algorithm extracts useful knowledge from large data sets obtained from manufacturing processes and represents this knowledge using “if/then” decision rules. Application of the data mining algorithm developed in this paper is illustrated with an industrial example of rapid tool making (RTM). RTM is a technology that adopts rapid prototyping (RP) techniques, such as spray forming, and applies them to tool and die making. A detailed discussion on how to control the output of the manufacturing process using the results obtained from the data mining algorithm is also presented. Compared to other data mining methods, such decision trees and neural networks, the advantage of the proposed approach is its accuracy, computational efficiency, and ease of use.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45889/1/170_2004_Article_2367.pd
Microstructure Effects on Electrochemical Characteristics for Plasma Spray Deposited LiFePO4 Films
The electrochemical behavior of composite electrodes used in Li ion batteries is influenced by factors such as microstructural characteristics (e.g. particle size, crystallinity, porosity etc.) and composition. For optimal performance of electrodes these factors are of utmost concern and serve as motivation for research in this field. In this report, we investigated LiFePO4 films synthesized by a novel plasma spray deposition method, which has capability for direct deposition of LiFePO4 films with carbon. This enables electrode characterizations to be carried out at the film level, without recourse to steps involving powder material handling. In this report microstructure and electrochemical properties of LiFePO4 films were investigated to elucidate their unique characteristics. Our studies show that factors such as porosity and microstructure of the films affect the electrochemical properties. The mechanical compression and thermal annealing experiments are shown to affect the electrochemical characteristics of LiFePO4 films. We show that annealing treatment leads to a drastic improvement in impedance and charge-discharge capacities for the LiFePO4 films. These treatments could serve to improve the electrode properties of porous film based materials for Li ion batteries and help us develop new film based materials for energy storage applications
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System Identification of Fused Filament Fabrication Additive Manufacturing Extrusion and Spreading Dynamics
In fused filament fabrication additive manufacturing, polymer extrusion and spreading dynamics affect
build quality in both surface finish and mechanical properties. The state of the art in extrusion modeling
and control is identification and compensation of a fixed first order pole with a linear model of the
system. However, physical nonlinearities cause deviation of this pole in practice. To advance the aim of
slicing using accurate nonlinear dynamic models, this work presents a system and procedure for
automated measurement of dynamic bead extrusion. The system uses a belt printer, iFactory3D One Pro,
with nozzle tilted 45 degrees from the build belt, and a snapshot 3D scanner. Single layer prints in
polylactic acid (PLA) are scanned and then automatically ejected. The gcode for the single bead print
holds the gantry speed fixed or extrusion speed constant while the extrusion flow rate or gantry speed is
varied as a step input signal in space. The experiment design matrix varied two variables: gantry speed
and extrusion flow rate. Time constants are fitted to bead area signals that are extracted from the scan data
to obtain nonlinear models. Depending on the experiment condition, the percent difference between the
highest time constant and the lowest time constant ranged from 279% to 61%, confirming the high
nonlinearity of the extrusion system in FFF 3D printers. Additionally, measurements are performed on a
cartesian 3D printer with a 2D scanner to test applicability of the methods to a general audience and
verify observed trends. It was observed that larger steps in extrusion velocity for a constant X-Axis
velocity, yielded smaller time constants, while the same steps in velocity using a constant extrusion
velocity condition with variable X-Axis velocity, yielded the opposite trend. Moreover, the time constants
for a step up in extrusion velocity yielded higher overall values in time constant when compared to step
down conditions.Mechanical Engineerin
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Benchmarking the Tensile Properties of Polylactic Acid (PLA) Recycled Through Fused Granule Fabrication Additive Manufacturing
To progress toward a circular economy of thermoplastic polymers, the adoption of 3D
printers to make functional articles can facilitate distributed recycling. To this end, the
mechanical degradation of polymers through multiple recycling cycles must be quantified. This
work presents a procedure and benchmark dataset of tensile property degradation for polylactic
acid (PLA) feedstock in multiple recycling passes with a fused granule fabrication process. To
establish recycling with minimal processing (shredding and sieving), modifications were
required to the granule feeding hopper of the 3D printer. Two distinct orientations were chosen
to obtain tensile test coupons. These coupons were die-cut from machined 3D printed rectangular
cross-section tubes, with one orientation along the bead (0°) and the other perpendicular to it
(90°). Tensile properties are presented for 3D printed virgin material and one, two, three, and
four passes of recycling. In terms of print orientation, the results indicate that samples pulled at
0° and 90° exhibited similar mechanical properties. However, there was an average decrease of
3.1% in ultimate tensile strength and a 1.7% decrease in elastic modulus for the samples along
90° orientation for all recycling passes. The samples along 0° demonstrated a 13.7% higher
strain at fracture compared to those along 90°. Regarding the number of recycling passes, the
findings suggest that the mechanical characteristics of PLA remain largely unaffected even after
undergoing four recycling cycles. However, when the material is pulled in the direction of the
bead, a 3.09% decrease in ultimate tensile strength is observed in the fourth recycling pass. The
elastic modulus and strain at fracture did not exhibit a clear trend. It is important to note that the
testing results display some variability, which can be attributed to a combination of stochasticity
in the printing process and the preparation procedure employed.Mechanical Engineerin
Studies on the mechanisms of heterogeneous nucleation of grains and pores in aluminum castings
In the present study, a fundamental theoretical and experimental investigation has been carried out on the mechanisms of heterogeneous nucleation of grains and pores in aluminum castings. A direct addition technique has been developed to introduce known types and quantities of inoculants into liquid aluminum alloys, irrespective of their wettability and chemical reactivity while preserving the surface characteristics and melt chemistry. Many different types of inoculants such as: , SiC, MgO, , TiB, TiC, SrO and Sr(OH) have been successfully added into liquid aluminum alloys, yielding single particulate distributions while avoiding incorporation of naturally occuring oxide films.The commercial grain refining practice of Al and its alloys has been experimentally simulated by introducing synthetic TiB and TiC crystals into melts containing dissolved Ti. Experimental findings indicate that in the absence of dissolved Ti, TiB crystallites alone do not nucleate -Al. TiC particles which are generally believed to be the nucleating substrate are unstable and form various complex carbides. In the presence of dissolved Ti even below the peritectic level, an interfacial layer of TiAl is formed at the TiB/melt interface which subsequently nucleates the -Al. A 'duplex' nucleation mechanism is proposed based on the solute segregation phenomenon to the substrate/melt interface. In the case of hypoeutectic Al-Si alloy, this interfacial layer was found to be a ternary compound of Al-Si-Ti, however, a drastic drop in the peritectic solidification temperature presumably reduces its grain refining potency at higher Si content.Particles which do not nucleate the solid phase and/or do not get engulfed by the growing solid, are continuously rejected by the solid/liquid (S/L) interface until the end of local solidification. These substrates act as a barrier to the fluid flow as well as to the diffusion field at the S/L interface, giving rise to enhanced gas segregation and viscous pressure drop. A novel theoretical mechanism for the heterogeneous nucleation of pores has been proposed, based on this behaviour of foreign particles at the advancing S/L interface. Mathematical analyses have been employed to predict the gas segregation and pressure drop in the gap between the particle and the S/L interface. An order of magnitude analysis is done, and it is shown that pressures in the range of the activation barrier can be obtained in normal castings. To substantiate the mechanism further, experimental studies were carried out by introducing various possible inclusions into liquid aluminum. The experimental findings are in line with the theoretical predictions
Vahram Avagyan Scanned Three-Dimensional Model Matching and Comparison Algorithms for Manufacturing Applications
Data mining algorithm for manufacturing process control
In this paper, a new data mining algorithm based on the rough sets theory is presented for manufacturing process control. The algorithm extracts useful knowledge from large data sets obtained from manufacturing processes and represents this knowledge using “if/then” decision rules. Application of the data mining algorithm developed in this paper is illustrated with an industrial example of rapid tool making (RTM). RTM is a technology that adopts rapid prototyping (RP) techniques, such as spray forming, and applies them to tool and die making. A detailed discussion on how to control the output of the manufacturing process using the results obtained from the data mining algorithm is also presented. Compared to other data mining methods, such decision trees and neural networks, the advantage of the proposed approach is its accuracy, computational efficiency, and ease of use.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45889/1/170_2004_Article_2367.pd
Microsturcutre Effects on Electrochemical Characteristics for Plasma Spray Deposited LiFePO4 Films
The electrochemical behavior of composite electrodes used in Li ion batteries is influenced by factors such as microstructural characteristics (e.g. particle size, crystallinity, porosity etc.) and composition. For optimal performance of electrodes these factors are of utmost concern and serve as motivation for research in this field. In this report, we investigated LiFePO4 films synthesized by a novel plasma spray deposition method, which has capability for direct deposition of LiFePO4 films with carbon. This enables electrode characterizations to be carried out at the film level, without recourse to steps involving powder material handling. In this report microstructure and electrochemical properties of LiFePO4 films were investigated to elucidate their unique characteristics. Our studies show that factors such as porosity and microstructure of the films affect the electrochemical properties. The mechanical compression and thermal annealing experiments are shown to affect the electrochemical characteristics of LiFePO4 films. We show that annealing treatment leads to a drastic improvement in impedance and charge-discharge capacities for the LiFePO4 films. These treatments could serve to improve the electrode properties of porous film based materials for Li ion batteries and help us develop new film based materials for energy storage applications