Miamisburg, OH, United States
Miamisburg, OH, United States

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Gao Y.,Illinois Institute of Technology | Zhou Y.,Illinois Institute of Technology | Wu B.,Illinois Institute of Technology | Tao S.,Illinois Institute of Technology | And 2 more authors.
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2011

Silicon carbide, due to its unique properties, has many promising applications in optics, electronics, and other areas. However, it is difficult to micromachine using mechanical approaches due to its brittleness and high hardness. Laser ablation can potentially provide a good solution for silicon carbide micromachining. However, previous studies of silicon carbide ablation by nanosecond laser pulses at infrared wavelengths are very limited on material removal mechanism, and the mechanism has not been well understood. In this paper, experimental study is performed for silicon carbide ablation by 1064 nm and 200 ns laser pulses through both nanosecond time-resolved in situ observation and laser-ablated workpiece characterization. This study shows that the material removal mechanism is surface vaporization, followed by liquid ejection (which becomes clearly observable at around 1 μs after the laser pulse starts). It has been found that the liquid ejection is very unlikely due to phase explosion. This study also shows that the radiation intensity of laser-induced plasma during silicon carbide ablation does not have a uniform spatial distribution, and the distribution also changes very obviously when the laser pulse ends. © 2011 American Society of Mechanical Engineers.


Grant
Agency: Department of Health and Human Services | Branch: | Program: STTR | Phase: Phase I | Award Amount: 53.42K | Year: 2012

DESCRIPTION (provided by applicant): Each year in the US, approximately 600,000 total knee replacement (TKR) surgeries are performed at a total annual cost of 15B and nearly 4.5M Americans are currently living with a TKR implant. The survival rate of TKRdevices declines dramatically after ten years of use due primarily to mechanical wear. The objective of this STTR project is radically improve the durability of TKRs by modifying them to enhance the performance of the lubricating synovial fluid. The current paradigm for combating implant wear is to minimize friction by employing ultra-smooth sliding surfaces. In contrast, our approach will add to the implant's femoral component a surface texture that is designed to create hydrodynamic lubrication at low sliding velocities. Newly available ultra short pulse lasers will b used to create the designed texture on a CoCr femoral component in the form of arrays of micron-scale dimples. The lasers will achieve this in a manner that does not adversely affect the surface roughness between dimples, or the intrinsically excellent wear properties of the material. This Phase 1 project will verify the hypothesis that a surface so textured can generate full fluid lubrication at realistic knee joint sliding velocities to reduce friction and wear that eventually lead to implant failure. This research has the potential to shift current paradigms about implant bearing surfaces. This knowledge could produce a new generation of radically different, longer-lasting orthopedic implants. The method laser texturing method for modifying the implants is an established industrial process that is affordable and will allow near term transition of the lubrication enhancement technology for the benefit of patients and overall savings to the health care system. PUBLIC HEALTH RELEVANCE: Nearly 4.5 million Americans are currently benefitting from total knee replacement (TKR) implants, and new surgeries are being performed a rate of 600,000 (and 15B) per year and accelerating. The statistical failure rate of TKR implants increases dramatically after 10 years of service. This project seeks to greatly reduce wear and extend life of TKRs to avoid patient pain and disability, and reduce health care costs and risks associated with complicationsand revision surgery. 1


Schrand A.M.,U.S. Air force | Stacy B.M.,U.S. Air force | Payne S.,Mound Laser and Photonics Center Inc. | Dosser L.,Mound Laser and Photonics Center Inc. | Hussain S.M.,U.S. Air force
ACS Applied Materials and Interfaces | Year: 2011

Near infrared (NIR) light, which spans wavelengths from ∼700-1100 nm holds particular promise in bionanotechnology-enabled applications because both NIR light and nanoparticles (NPs) have the potential for remote activation leading to exquisite localization and targeting scenarios. In this study, aqueous solutions of carbon and metal-based NPs (carbon black, single-walled carbon nanotubes, silver nanoparticles and copper nanoparticles) were exposed to continuous NIR laser (λ = 1064 nm) irradiation at powers of 2.2W and 4.5W. The differential heating of bulk aqueous suspension of NPs with varying physicochemical properties revealed maximum temperatures of 67 °C with visible evidence of condensation and bubble formation. The basis of the NP heating is due to the strong intrinsic optical absorbance in the NIR spectral window and the transduction of this NIR photon energy into thermal energy. In this regard, UV-vis measurements can accurately predict NP heating kinetics prior to NIR irradiation. Further, a uniform thermodynamic heating model demonstrates close agreement with the experimental data for the low NIR-absorbing NPs. However, the uniform thermodynamic heating model used in this study does not accurately portray the energy release upon localized NP heating because of bubble formation for the highly absorbing NPs. Therefore, this study reveals the differential heating kinetics of NPs excited with NIR with implications in the development of novel NIR-NP-based systems. © 2011 American Chemical Society.


Jacobsen R.L.,Mound Laser and Photonics Center Inc. | Randi J.,Penn State Electro Optics Center | Payne S.,Mound Laser and Photonics Center Inc.
29th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2010 - Congress Proceedings | Year: 2010

This paper provides an update on experiments in the use of pulsed laser ablation (10 ps to 120 ns) as a technique for mitigation of surface stress and damage in silicon carbide is provided. SiC is of interest for a wide range of applications due to its thermal, optical, and electrical properties as well as its dimensional stability. However, concerns about handling damage and unpredictable breakage may limit its use. Machining, grinding and even polishing of this brittle material leaves a damaged surface layer of depth approximately proportional to the size of the abrasive used to finish it. This damage layer is a potential source of crack initiation, and its mitigation is desirable. The damage layer is accompanied by compressive stress. Measurements of the changes in this stress can be used to track improvements in the surface. The Twyman method is used to demonstrate and quantify the degree to which laser ablation can be used to remove the damage layer in variously prepared samples of SiC, and potentially lead to improved reliability of this material and other brittle materials.


Ganti S.,Wright State University | Gault Z.,Wright State University | Smith S.I.V.,Wright State University | Deibel J.A.,Wright State University | And 3 more authors.
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2012

Finite element method simulations of periodically corrugated metal terahertz wire waveguides have been conducted with concurrent analysis done on both the near-field confinement properties and the far-field emission properties at the end of the waveguides. This modeling was used to guide the choice of design parameters for the fabrication of waveguides with laser micromachining. The waveguides were characterized with a fibercoupled terahertz time-domain spectroscopy and imaging system. The propagation properties as well as the frequency dependent diffraction at the end of the wire waveguides were examined and compared to straight, non-engineered metallic wire waveguides. © Springer Science+Business Media New York 2012.


Zhang W.-D.,Wright State University | Middendorf J.R.,Mound Laser and Photonics Center Inc. | Brown E.R.,Wright State University
Applied Physics Letters | Year: 2015

An Er:GaAs-based 1550-nm CW photomixer is demonstrated. The related mechanism is extrinsic photoconductivity with optical absorption between the localized deep levels created by the Er and the extended states above the conduction band edge of GaAs. With the power boost made possible by a fiber-coupled erbium-doped-fiber amplifier, the Er:GaAs photomixers, operating at 1550 nm, radiate THz power levels easily measured by a Golay cell, and display a power spectrum having a -3 dB roll-off frequency of 307 GHz. This corresponds to a photocarrier lifetime of 520 fs, in good agreement with a previous measurement of the bandwidth of the same material in a photoconductive switch. © 2015 AIP Publishing LLC.


Druffner C.,Mound Laser and Photonics Center Inc. | Nalladega V.,University of Dayton | Na J.K.,University of Dayton
AIP Conference Proceedings | Year: 2011

To increase the power generating capacity of a wind turbine composite turbine blade manufacturers have been increasing the size of blades. Current utility-scale windmills are equipped with blades ranging from 40 m (130 ft) to 90 m (300 ft) in their sweep diameter. The increased blade size brings greater structural and safety demands. Recent blade recalls and field failures highlights the market need for sensors capable of part quality inspections on manufacturing line and for structural health monitoring (SHM) of the composites in service. An ultrasonic surface wave sensor technology based on interdigitization transduction (IDT) has been developed that can inspect and detect defects in the composite blades. The current work covers the design, fabrication, and characterization of the IDT sensors. The sensor characterization, coverage area, and detection capability for a variety of defects such as impact, cracking and delamination will be discussed. © 2011 American Institute of Physics.


Nalladega V.,University of Dayton | Na J.K.,University of Dayton | Druffner C.,Mound Laser and Photonics Center Inc.
AIP Conference Proceedings | Year: 2011

Interdigital transducers (IDT) generate and receive ultrasonic surface waves without the complexity involved with secondary devices such as angled wedges or combs. The IDT sensors have been successfully applied for the NDE of homogeneous materials like metals in order to detect cracks and de-bond. However, these transducers have not been yet adapted for complex and anisotropic materials like fiber-reinforced composites. This work presents the possibility of using IDT sensors for monitoring structural damages in wind turbine blades, typically made of fiberglass composites. IDT sensors with a range of operating frequency between 250 kHz and 1 MHz are initially tested on representative composite test panels for ultrasonic surface wave properties including beam spread, propagation distance and effect of material's anisotropy. Based on these results, an optimum frequency range for the IDT sensor is found to be 250-500 kHz. Subsequently, IDT sensors with operating frequency 500 kHz are used to detect and quantify artificial defects created in the composite test samples. Discussions are made on the interaction of ultrasonic fields with these defects along with the effects of fiber directionality and composite layer stacking. © 2011 American Institute of Physics.


Na J.K.,University of Dayton | Nalladega V.,University of Dayton | Druffner C.,Mound Laser and Photonics Center Inc.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Polyester resin based glass fiber reinforced composite panels obtained from a local windmill turbine blade part manufacturing company are used to evaluate the performance of inter-digital transducer (IDT) surface wave transducers. Interaction of surface waves with fiberglass layers is addressed in this work. Additionally, artificially created flaws such as cracks, impact damage and delamination are also studied in terms of amplitude changes in order to attempt to quantify the size, location and severity of damage in the test panels. As a potential application to the structural health monitoring (SHM) of windmill turbine blades, the coverage distance within the width of the sound field is estimated to be over 80 cm when a set of IDT sensors consisted of one transmitter and two receivers in a pitch-catch mode. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Tao S.,Illinois Institute of Technology | Jacobsen R.L.,Mound Laser and Photonics Center Inc. | Wu B.,Illinois Institute of Technology
Applied Physics Letters | Year: 2010

Investigations have been performed on the physical mechanisms of picosecond laser ablation of silicon carbide at 355 and 1064 nm, which have not been well understood yet. The study shows that the low-fluence ablation rates are close for 355 and 1064 nm, and the dominant material removal mechanism should be surface evaporation. At fluences above ∼2J/ cm2, the ablation rate increases very quickly for 355 nm, and the associated dominant mechanism is very likely to be critical point phase separation. For 1064 nm, the ablation rate variation with fluence above ∼2 J/ cm2 follows the same trend as that for low fluences, and the mechanism should remain as surface evaporation. © 2010 American Institute of Physics.

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