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- Title
- INSTRUMENTED NANOINDENTATION STUDIES OF DEFORMATION IN SHAPE MEMORY ALLOYS.
- Creator
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Rajagopalan, Sudhir, Vaidyanathan, Rajan, University of Central Florida
- Abstract / Description
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Near equi-atomic nickel titanium (NiTi) shape memory alloys (SMAs) are a class of materials characterized by their unique deformation behavior. In these alloys, deformation mechanisms such as mechanical twinning and stress induced phase transformation between a high symmetry phase (austenite) and a low symmetry phase (martensite) additionally occur and influence mechanical behavior and thus their functionality. Consequently, applications of SMAs usually call for precise phase transformation...
Show moreNear equi-atomic nickel titanium (NiTi) shape memory alloys (SMAs) are a class of materials characterized by their unique deformation behavior. In these alloys, deformation mechanisms such as mechanical twinning and stress induced phase transformation between a high symmetry phase (austenite) and a low symmetry phase (martensite) additionally occur and influence mechanical behavior and thus their functionality. Consequently, applications of SMAs usually call for precise phase transformation temperatures, which depend on the thermomechanical history and the composition of the alloy. Instrumented indentation, inherently a mechanical characterization technique for small sampling volumes, offers a cost effective means of empirically testing SMAs in the form of centimeter scaled buttons prior to large-scale production. Additionally, it is an effective probe for intricate SMA geometries (e.g., in medical stents, valves etc.), not immediately amenable to conventional mechanical testing. The objective of this work was to study the deformation behavior of NiTi SMAs using instrumented indentation. This involved devising compliance calibration techniques to account for instrument deformation and designing spherical diamond indenters. Substantial quantitative information related to the deformation behavior of the shape memory and superelastic NiTi was obtained for the first time, as opposed to existing qualitative indentation studies. For the case of shape memory NiTi, the elastic modulus of the B19' martensite prior to twinning was determined using spherical indentation to be about 101 GPa, which was comparable to the value from neutron diffraction and was substantially higher than typical values reported from extensometry (68 GPa in this case). Twinning at low stresses was observed from neutron diffraction measurements and was attributed to reducing the elastic modulus estimated by extensometry. The onset of predominantly elastic deformation of the twinned martensite was identified from the nanoindentation response and the elastic modulus of the twinned martensite was estimated to be about 17 GPa. Finite element modeling was used to validate the measurements. For the case of the superelastic NiTi, the elastic modulus of the parent austenite was estimated to be about 62 GPa. The onset of large-scale stress induced martensite transformation and its subsequent elastic deformation were identified from the nanoindentation response. The effect of cycling on the mechanical behavior of the NiTi specimen was studied by repeatedly indenting at the same location. An increase in the elastic modulus value for the austenite and a decrease in the associated hysteresis and residual depth after the initial few cycles followed by stabilization were observed. As for the case of shape memory NiTi, finite element modeling was used to validate the measurements. This work has initiated a methodology for the quantitative evaluation of shape memory and superelastic NiTi alloys with instrumented spherical indentation. The aforementioned results have immediate implications for optimizing thermomechanical processing parameters in prototype button melts and for the mechanical characterization of intricate SMA geometries (e.g., in medical stents, valves etc.) This work was made possible by grants from NASA (NAG3-2751) and NSF (CAREER DMR-0239512) to UCF.
Show less - Date Issued
- 2005
- Identifier
- CFE0000652, ucf:46502
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000652
- Title
- CRYOGENIC SHAPE MEMORY ALLOY ACTUATORS FOR SPACEPORT TECHNOLOGIES: MATERIALS CHARACTERIZATION AND PROTOTYPE TESTING.
- Creator
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Lemanski, Jennifer, Vaidyanathan, Rajan, University of Central Florida
- Abstract / Description
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Shape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of...
Show moreShape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of large forces associated with the strain recovery, smooth and controlled movements, large movement to weight ratio, high reliability, and spark-free operation. The objective of this work is the further development and testing of a cryogenic thermal conduction switch as part of NASA funded projects. The switch was developed to provide a variable conductive pathway between liquid methane and liquid oxygen dewars in order to passively regulate the methane temperature. Development of the switch concept has been continued in this work by utilizing Ni-Ti-Fe as the active SMA element. Ni-Ti-Fe exhibits the shape memory effect at cryogenic temperatures, which makes it well suited for low temperature applications. This alloy is also distinguished by an intermediate phase change known as the rhombohedral or R-phase, which is characterized by a small hysteresis (typically 1-2 deg C) and offers the advantage of precise control over a set temperature range. For the Ni-Ti-Fe alloy used, its thermomechanical processing, subsequent characterization using dilatometry and differential scanning calorimetry and implementation in the conduction switch configuration are addressed. This work was funded by grants from NASA KSC (NAG10-323) and NASA GRC (NAG3-2751).
Show less - Date Issued
- 2005
- Identifier
- CFE0000501, ucf:46448
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000501
- Title
- THERMO-MECHANICAL CHARACTERIZATION OF HIGH-TEMPERATURE SHAPE MEMORY NI-TI-PD WIRES.
- Creator
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Fox, Matthew, Vaidyanathan, Rajan, University of Central Florida
- Abstract / Description
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Actuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying...
Show moreActuator applications of shape memory alloys have typically been limited by their phase transformation temperatures to around 100 degrees C. However, recently with a focus on aerospace and turbomachinery applications there have been successful efforts to increase the phase transformation temperatures. Several of these alloy development efforts have involved ternary and quaternary elemental additions (e.g., Pt, Pd, etc.) to binary NiTi alloys. Experimentally assessing the effects of varying composition and thermo-mechanical processing parameters can be cost intensive, especially when expensive, high-purity elemental additions are involved. Thus, in order to save on development costs there is value in establishing a methodology that facilitates the fabrication, processing and testing of smaller specimens, rather than larger specimens from commercial billets. With the objective of establishing such a methodology, this work compares thermo-mechanical test results from bulk dog-bone tensile Ni29.5Ti50.5Pd20 samples (7.62 mm diameter) with that of thin wires (100 μm-150 µm diameter) extracted from comparable, untested bulk samples by wire electrical-discharge machining (EDM). The wires were subsequently electropolished to different cross-sections, characterized with Scanning Electron Microscopy, Transmission Electron Microscopy and Energy Dispersive X-Ray Spectroscopy to verify the removal of the heat affected zone following EDM and subjected to Laser Scanning Confocal Microscopy to accurately determine their cross-sections before thermo-mechanical testing. Stress-strain and load-bias experiments were then performed on these wires using a dynamic mechanical analyzer and compared with results established in previous studies for comparable bulk tensile specimens. On comparing the results from a bulk tensile sample with that of the micron-scale wires, the overall thermomechanical trends were accurately captured by the micron-scale wires for both the constrained recovery and monotonic tensile tests. Specifically, there was good agreement between the stress-strain response in both the martensitic and austenitic phases, the transformation strains at lower stresses in constrained recovery, and the transformation temperatures at higher stresses in constrained recovery. This work thus validated that carefully prepared micron-diameter samples can be used to obtain representative bulk thermo-mechanical properties, and is useful for fabricating and optimizing composition and thermo-mechanical processing parameters in prototype button melts prior to commercial production. This work additionally assesses potential applications of high temperature shape memory alloy actuator seals in turbomachinery. A concept for a shape memory alloy turbine labyrinth seal is also presented. Funding support from NASA's Fundamental Aeronautics Program, Supersonics Project (NNX08AB51A) and Siemens Energy is acknowledged.
Show less - Date Issued
- 2009
- Identifier
- CFE0002813, ucf:48102
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002813
- Title
- Thermomechanical Behavior of High-Temperature Shape Memory Alloy NiTiPdPt Actuators.
- Creator
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Nicholson, Douglas, Vaidyanathan, Rajan, Kumar, Ranganathan, Chen, Ruey-Hung, University of Central Florida
- Abstract / Description
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To date the commercial use of shape memory alloys (SMAs) has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the -100 to 100 (&)#186;C range. In an ongoing effort to develop high-temperature shape memory alloys (HTSMAs), ternary and quaternary additions are being made to binary NiTi to form NiTi-X (e.g., X: Pd, Pt, Au and Hf) alloys. Stability and repeatability can be further increased at these higher temperatures by limiting the stress, but the...
Show moreTo date the commercial use of shape memory alloys (SMAs) has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the -100 to 100 (&)#186;C range. In an ongoing effort to develop high-temperature shape memory alloys (HTSMAs), ternary and quaternary additions are being made to binary NiTi to form NiTi-X (e.g., X: Pd, Pt, Au and Hf) alloys. Stability and repeatability can be further increased at these higher temperatures by limiting the stress, but the tradeoff is reduced work output and stroke. However, HTSMAs operating at decreased stresses can still be used effectively in actuator applications that require large strokes when used in the form of springs. The overall objective of this work is to facilitate the development of HTSMAs for use as high-force actuators in active/adaptive aerospace structures.A modular test setup was assembled with the objective of acquiring stroke, stress, temperature and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were evaluated under both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Recognizing that evolution in the material microstructure results in changes in geometry and vice versa in HTSMA springs, the objective of the present study also included assessing the contributions from the material microstructural evolution, by eliminating contributions from changes in geometry, to overall HTSMA spring performance. The finite element method (FEM) was used to support the analytical analyses and provided further insight into the behavior and heterogeneous stress states that exist in these spring actuators.Furthermore, with the goal of improving dimensional stability there is a need to better understand the microstructural evolution in HTSMAs that contributes to irrecoverable strains. Towards this goal, available Ni29.5Ti50.5Pd20 neutron diffraction data (from a comparable HTMSA alloy without the solid solution strengthening offered by the Pt addition) were analyzed. The data was obtained from in situ neutron diffraction experiments performed on Ni29.5Ti50.5Pd20 during compressive loading while heating/cooling, using the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory. Specifically, in this work emphasis was placed on neutron diffraction data analysis via Rietveld refinement and capturing the texture evolution through inverse pole figures. Such analyses provided quantitative information on the evolution of lattice strain, phase volume fraction (including retained martensite that exists above the austenite finish temperature) and texture (martensite variant reorientation and detwinning) under temperature and stress. Financial support for this work from NASA's Fundamental Aeronautics Program Supersonics Project (NNX08AB51A), Subsonic Fixed Wing Program (NNX11AI57A) and the Florida Center for Advanced Aero-Propulsion (FCAAP) is gratefully acknowledged. It benefited additionally from the use of the Lujan Neutron Scattering Center at Los Alamos National Laboratory, which is funded by the Office of Basic Energy Sciences (Department of Energy) and is operated by Los Alamos National Security LLC under DOE Contract DE-AC52-06NA25396.
Show less - Date Issued
- 2011
- Identifier
- CFE0004147, ucf:49059
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004147
- Title
- Low Strain Rate Studies of Alumina Epoxy Composites using Piezospectroscopy.
- Creator
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Jones, Ashley, Raghavan, Seetha, Gordon, Ali, Vaidyanathan, Rajan, University of Central Florida
- Abstract / Description
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Particulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particle-matrix bonding and therefore improved stiffness and load...
Show moreParticulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particle-matrix bonding and therefore improved stiffness and load transfer in the composite. Photo-luminescent ?-alumina nanoparticles when embedded in an epoxy matrix allow for the added benefit of in situ measurements at low strain rates to provide stress-sensitive information using the particle piezospectroscopic (PS) property. To investigate the low strain rate behavior, cylindrical specimens of alumina-epoxy composites with varying volume fractions of alumina were fabricated using a casting process to ensure minimal surface finishing and reduced manufacturing time. The results illustrate the capability of alumina nanoparticles to act as diagnostic sensors to measure the stress-induced shifts of the spectral R-line peaks resulting from low compressive strain rates. The range of PS coefficients measured, -3.15 to -5.37 cm^-1/GPa for R1 and -2.62 to -5.39 cm^-1/GPa for R2, correlate well with static test results of similar volume fractions. Results reveal a general trend of increasing sensitivity of the PS coefficients with increasing strain rate when compared to similar materials under static conditions. In contrast to static results, at a given strain rate, the PS coefficients show varying degrees of sensitivity for each volume fraction. This information can be used to determine the time-dependent micro-scale stresses the nanoparticles sustain during composite loading. Additionally, this work facilitates failure prediction by monitoring upshifts in the PS information. Calibration of the in situ diagnostic stress sensing capabilities of varying volume fractions of alumina nanocomposites under quasi-static strain rates in this work sets the precedent for future studies at high strain rates.
Show less - Date Issued
- 2013
- Identifier
- CFE0005099, ucf:50728
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005099
- Title
- Multiscale simulation of laser ablation and processing of semiconductor materials.
- Creator
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Shokeen, Lalit, Schelling, Patrick, Kar, Aravinda, Vaidyanathan, Rajan, Su, Ming, Kara, Abdelkader, University of Central Florida
- Abstract / Description
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We present a multiscale model of laser-solid interactions in silicon based on an empirical potential developed under conditions of strong electronic excitations. The parameters of the interatomic potential depends on the temperature of the electronic subsystem Te, which is directly related to the density of the electron-hole pairs and hence the number of broken bonds. We analyze the dynamics of this potential as a function of electronic temperature Te and lattice temperature Tion. The...
Show moreWe present a multiscale model of laser-solid interactions in silicon based on an empirical potential developed under conditions of strong electronic excitations. The parameters of the interatomic potential depends on the temperature of the electronic subsystem Te, which is directly related to the density of the electron-hole pairs and hence the number of broken bonds. We analyze the dynamics of this potential as a function of electronic temperature Te and lattice temperature Tion. The potential predicts phonon spectra in good agreement with finite-temperature density-functional theory (DFT), including the lattice instability induced by the high electronic excitations. For 25fs pulse, a wide range of fluence values is simulated resulting in heterogeneous melting, homogenous melting, and ablation. The results presented demonstrate that phase transitions can usually be described by ordinary thermal processes even when the electronic temperature Te is much greater than the lattice temperature TL during the transition. However, the evolution of the system and details of the phase transitions depend strongly on Te and corresponding density of broken bonds. For high enough laser fluence, homogeneous melting is followed by rapid expansion of the superheated liquid and ablation. Rapid expansion of the superheated liquid occurs partly due to the high pressures generated by a high density of broken bonds. As a result, the system is readily driven into the liquid-vapor coexistence region, which initiates phase explosion. The results strongly indicates that phase explosion, generally thought of as an ordinary thermal process, can occur even under strong non-equilibrium conditions when Te (>)(>)TL. In summary, a detailed investigation of laser-solid interactions in silicon is presented for femtosecond laser pulse that yields strong far-from-equilibrium conditions.
Show less - Date Issued
- 2012
- Identifier
- CFE0004599, ucf:49206
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004599
- Title
- Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys.
- Creator
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Benafan, Othmane, Vaidyanathan, Rajan, Gordon, Ali, Notardonato, William, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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The unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited...
Show moreThe unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited application in other fields. This limitation arises from the complexities of prevailing microstructural mechanisms that lead to dimensional instabilities during repeated thermomechanical cycling. Most of these mechanisms are still not fully understood, and for the most part unexplored. The objective of this work was to investigate these deformation and transformation mechanisms that operate within the low temperature martensite and high temperature austenite phases, and changes between these two states during thermomechanical cycling. This was accomplished by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The primary focus was to investigate the thermomechanical response of a polycrystalline Ni49.9Ti50.1 (in at.%) shape memory alloy under uniaxial deformation conditions. Starting with the deformation of the cubic austenitic phase, the microstructural mechanisms responsible for the macroscopic inelastic strains during isothermal loading were investigated over a broad range of conditions. Stress-induced martensite, retained martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. This isothermal deformation was found to be a quick and efficient method for creating a strong and stable two-way shape memory effect.The evolution of inelastic strains with thermomechanical cycling of the same NiTi alloy, as it relates to the alloy stability, was also studied. The role of pre-loading the material in the austenite phase versus the martensite phase as a function of the active deformation modes (deformation processes as revealed in this work) were investigated from a macroscopic and microstructural perspective. The unique contribution from this work was the optimization of the transformation properties (e.g., actuation strain) as a function of deformation levels and pre-loading temperatures. Finally, the process used to set actuators, referred to as shape setting, was investigated while examining the bulk polycrystalline NiTi and the microstructure simultaneously through in situ neutron diffraction at stress and temperature. Knowledge gained from the binary NiTi study was extended to the investigation of a ternary Ni-rich Ni50.3Ti29.7Hf20 (in at.%) for use in high-temperature, high-force actuator applications. This alloy exhibited excellent dimensional stability and high work output that were attributed to a coherent, nanometer size precipitate phase that resulted from an aging treatment. Finally, work was initiated as part of this dissertation to develop sample environment equipment with multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory. The developed capability will immediately aid in making rapid multiaxial measurements on shape memory alloys wherein the texture, strain and phase fraction evolution are followed with changes in temperature and stress.This work was supported by funding from the NASA Fundamental Aeronautics Program, Supersonics Project including (Grant No. NNX08AB51A). This work has also benefited from the use of the Lujan Neutron Scattering Center at LANSCE, which is funded by the Office of Basic Energy Sciences DOE. LANL is operated by Los Alamos National Security LLC under DOE Contract No. DE-AC52-06NA25396.
Show less - Date Issued
- 2012
- Identifier
- CFE0004496, ucf:49288
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004496
- Title
- Phonon Modulation by Polarized Lasers for Material Modification.
- Creator
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Chen, Sen-Yong, Kar, Aravinda, Vaidyanathan, Rajan, Harvey, James, Likamwa, Patrick, University of Central Florida
- Abstract / Description
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Magnetic resonance imaging (MRI) has become one of the premier non-invasive diagnostic tools, with around 60 million MRI scans applied each year. However, there is a risk of thermal injury due to radiofrequency (RF) induction heating of the tissue and implanted metallic device for the patients with the implanted metallic devices. Especially, MRI of the patients with implanted elongated devices such as pacemakers and deep brain stimulation systems is considered contraindicated. Many efforts,...
Show moreMagnetic resonance imaging (MRI) has become one of the premier non-invasive diagnostic tools, with around 60 million MRI scans applied each year. However, there is a risk of thermal injury due to radiofrequency (RF) induction heating of the tissue and implanted metallic device for the patients with the implanted metallic devices. Especially, MRI of the patients with implanted elongated devices such as pacemakers and deep brain stimulation systems is considered contraindicated. Many efforts, such as determining preferred MRI parameters, modifying magnetic field distribution, designing new structure and exploring new materials, have been made to reduce the induction heating. Improving the MRI-compatibility of implanted metallic devices by modifying the properties of the existing materials would be valuable.To evaluate the temperature rise due to RF induction heating on a metallic implant during MRI procedure, an electromagnetic model and thermal model are studied. The models consider the shape of RF magnetic pulses, interaction of RF pulses with metal plate, thermal conduction inside the metal and the convection at the interface between the metal and the surroundings. Transient temperature variation and effects of heat transfer coefficient, reflectivity and MRI settings on the temperature change are studied.Laser diffusion is applied to some titanium sheets for a preliminary study. An electromagnetic and thermal model is developed to choose the proper diffusant. Pt is the diffusant in this study. An electromagnetic model is also developed based on the principles of inverse problems to calculate the electromagnetic properties of the metals from the measured magnetic transmittance. This model is used to determine the reflectivity, dielectric constant and conductivity of treated and as-received Ti sheets. The treated Ti sheets show higher conductivity than the as-received Ti sheets, resulting higher reflectivity.A beam shaping lens system which is designed based on vector diffraction theory is used in laser diffusion. Designing beam shaping lens based on the vector diffraction theory offers improved irradiance profile and new applications such as polarized beam shaping because the polarization nature of laser beams is considered. Laser Pt diffusion are applied on the titanium and tantalum substrates using different laser beam polarizations. The concentration of Pt and oxygen in those substrates are measured using Energy Dispersive X-Ray Spectroscopy (EDS). The magnetic transmittance and conductivity of those substrates are measured as well. The effects of laser beam polarizations on Pt diffusion and the magnetic transmittance and conductivity of those substrates are studied. Treated Ti sheets show lower magnetic transmittance due to the increased conductivity from diffused Pt atoms. On the other hand, treated Ta sheets show higher magnetic transmittance due to reduced conductivity from oxidation. Linearly polarized light can enhance the Pt diffusion because of the excitation of local vibration mode of atoms.Laser Pt diffusion and thermo-treatment were applied on the Ta and MP35N wires. The Pt concentration in laser platinized Ta and MP35N wires was determined using EDS. The ultimate tensile strength, fatigue lives and lead tip heating in real MRI environment of those wires were measured. The lead tip hating of the platinized Ta wires is 42 % less than the as-received Ta wire. The diffused Pt increases the conductivity of Ta wires, resulting in more reflection of magnetic field. In the case of the platinized MP35N wire, the reduction in lead tip heating was only 1 (&)deg;C due to low concentration of Pt. The weaker ultimate tensile strength and shorter fatigue lives of laser-treated Ta and MP35N wires may attribute to the oxidation and heating treatment.
Show less - Date Issued
- 2012
- Identifier
- CFE0004500, ucf:49269
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004500