Laser machining apparatus Patent
Laser machining device with dielectric functioning as beam waveguide for mechanical and medical applications
Chioa, R. Y.↗
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Laser Machining of Melt Infiltrated Ceramic Matrix Composite
As interest grows in considering the use of ceramic matrix composites for critical components, the effects of different machining techniques, and the resulting machined surfaces, on strength need to be understood. This work presents the characterization of a Melt Infiltrated SiC/SiC composite material system machined by different methods. While a range of machining approaches were initially considered, only diamond grinding and laser machining were investigated on a series of tensile coupons. The coupons were tested for residual tensile strength, after a stressed steam exposure cycle. The data clearly differentiated the laser machined coupons as having better capability for the samples tested. These results, along with micro-structural characterization, will be presented.
Jarmon, D. C.↗
Simulated Performance of Laser-Machined Metamaterial Anti-reflection Coatings
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N. Farias↗
Fatigue Lives of Materials Cut by Lasers
Laser machining helps to balance high-speed rotating machinery. Report describes continuing studies of fatigue lives of materials cut by lasers. One long-term objective of such studies is use of laser machining to balance rotors operating at high speeds. To achieve objective, necessary to know relationship between effects of conventional and laser machining on fatigue lives of machined materials.
Martin, Michael R.↗
Closed-Loop Control of Laser Surface Treatment via Laser Induced Breakdown Spectroscopy
Current composite manufacturing rates need to be improved to meet the projected demand of on-demand mobility (ODM) and commercial aircraft transports. Some processes in the composite manufacturing chain require touch labor such as manual sanding of surfaces prior to bonding and installing thousands of mechanical fasteners in bonded primary structures to achieve Federal Aviation Administration (FAA) certification. The consequences are insufficient repeatability in bond quality resulting in increased manufacturing time. The FAA has indicated that robust process control is one potential means of certifying bondlines in primary structure. This work describes an integrated closed-loop control system between a laser machining system and laser induced breakdown spectroscopy (LIBS) instrumentation as a means of assuring bond performance and achieving certified composite bondlines. Preliminary results from in-situ treatment and inspection are presented. Results indicate that LIBS inspection and laser treatment can be conducted simultaneously to achieve high quality, reliable adhesive bonds.
Rodolfo Ledesma↗
Closed-Loop Control of Laser Surface Treatment via Laser Induced Breakdown Spectroscopy
Current composite manufacturing rates need to be improved to meet the projected demand of on-demand mobility (ODM) and commercial aircraft transports. Some processes in the composite manufacturing chain require touch labor such as manual sanding of surfaces prior to bonding and installing thousands of mechanical fasteners in bonded primary structures to achieve Federal Aviation Administration (FAA) certification. The consequences are insufficient repeatability in bond quality resulting in increased manufacturing time. The FAA has indicated that robust process control is one potential means of certifying bondlines in primary structure. This work describes an integrated closed-loop control system between a laser machining system and laser induced breakdown spectroscopy (LIBS) instrumentation as a means of assuring bond performance and achieving certified composite bondlines. Preliminary results from in-situ treatment and inspection are presented. Results indicate that LIBS inspection and laser treatment can be conducted simultaneously to achieve high quality, reliable adhesive bonds.
Rodolfo Ledesma↗
Laser power transmission.
Description of studies which have led to the design of a conceptual device in which the limitation of transforming heat into coherent radiation can be examined. By exploring the basic thermodynamic relationships controlling the operation of this device, it is concluded that a closed-cycle gasdynamic laser is possible in which all of the shaft energy supplied can be turned into laser radiation. Hence, it is possible in principle to convert heat into coherent radiation with approximately the same efficiency with which heat may be converted into electricity. By modifying the closed-cycle-gasdynamic-laser system, this system can be operated in reverse and the incoming radiation may be used to pump the gas in the loop so that shaft power can be extracted. By carefully controlling the temperature distribution in this machine, laser energy can be converted into useful shaft energy with an efficiency approaching 1 .
Ahlstrom, H. G.↗
Automatic inspection of silicon wafers
Laser machine scans wafers for contaminating particles which cause open circuits, short circuits, and other defects in integrated circuits and transfers good wafers to integrated circuit processing equipment. Machine is faster and more accurate than human operator using lightfield/dark field microscope.
Martin, M.↗
Fatigue Lives Of Laser-Cut Metals
Fatigue lives made to approach those attainable by traditional grinding methods. Fatigue-test specimens prepared from four metallic alloys, and material removed from specimens by manual grinding, by Nd:glass laser, and by Nd:YAG laser. Results of fatigue tests of all specimens indicated reduction of fatigue strengths of laser-fired specimens. Laser machining holds promise for improved balancing of components of gas turbines.
Martin, Michael R.↗
Long-life 3-axis satellite attitude sensing, phase 1
The purpose was to investigate the feasibility of new, moderate-cost, high reliability navigation sensors for high-altitude satellites, using stellar sources to obviate the use of gyroscopic devices. The primary investigation focused on the need for developing a star tracker model to replace an old star tracker which is still needed for current probe and satellite programs. One innovative element of the proposed star tracker was the design, development, and testing of technology components related to a phase scrambler plate. The purpose of the phase scrambler plate is to convert the impulse response of the optical system from a point image to a uniformly bright, square, angularly large, in-focus image of the star source. A collimated star source was built and tested. A breadboard star tracker with an 8 x 8 degree field of view was designed and built. It was tested in normal quad-cell mode (without the phase scrambler plate) and with the phase scrambler plate. Although the phase scrambler plate was crudely made, the performance of the star tracker breadboard was greatly improved using the phase scrambler plate, instead of system defocus. If further developed, the phase scrambler plate may be added as a low-cost retroconversion to any objective lens to greatly improve quad-cell or CCD array tracking; applications include star trackers, laser metrology, laser machining optics, and surveying instrumentation.
Arild, Tor↗
Fabrication and testing of carbon-carbon grids for ion optics
Ion optics measuring 16.5 cm in diameter and 1.0 mm in thickness were fabricated from carbon-carbon composites that were woven from a high-tensile-modulus carbon fiber. Plate flatness varied by less than 0.05 mm. Several methods were investigated for forming ion-extraction apertures in the carbon-carbon plates, including laser machining, mechanical drilling, and conventional electric discharge machining. Tests conducted using a quartz dilatometer indicated that the coefficient of thermal expansion of the carbon-carbon plates varied between -0.51 to -1.8 x 10 exp -6/degree C at plate temperatures between 173-773 K. Sputter-erosion experiments indicate that carbon-carbon erodes at a rate approximately 25 percent below molybdenum under the same conditions. These material properties indicate that carbon-carbon may be superior to molybdenum for use as ion optics electrodes for ion engines.
Garner, Charles E.↗
Development of a high-efficiency motor/generator for flywheel energy storage
This study addresses the design changes and extensions necessary to construct and test a working prototype of a motor/generator for a magnetically suspended flywheel energy storage system. The brushless motor controller for the motor was specified and the electronic commutation arrangement designed. The laminations were redesigned and fabricated using laser machining. Flux density measurements were made and the results used to redesign the armature windings. A test rig was designed and built, and the motor/generator was installed and speed tested to 9000 rpm. Experimental methods of obtaining the machine voltage and torque constants Kv and Kt, obtaining the useful air-gap flux density, and characterizing the motor and other system components are described. The measured Kv and Kt were approximately 40 percent greater than predicted by theory and initial experiment.
Lashley, Christopher↗
Laser Balancing
Mechanical Technology, Incorporated developed a fully automatic laser machining process that allows more precise balancing removes metal faster, eliminates excess metal removal and other operator induced inaccuracies, and provides significant reduction in balancing time. Manufacturing costs are reduced as a result.
Source record↗
Molecular Simulations of Ultrafast Radiation Induced Melting at Metal-Semiconductor Interfaces
Understanding radiation induced ultrafast melting at material interfaces is essential in designing robust electronic devices for aviation/space applications and in laser machining. While it is difficult to achieve the spatial and temporal resolution required to quantify the phenomenon experimentally, simulations can provide the detailed mechanisms of the structural changes that happen during phase transition. In this work, we use molecular simulations to study the effect of radiation damage on silicon carbide (SiC) - tungsten (W) interfaces which is of interest in high power electronics. A multi-scale approach is involved wherein the reactions at the interfaces are quantified using ab-initio molecular dynamics (MD) simulations and classical MD simulations are employed to understand the structural and diffusional changes across the material interface. Finally, coarse-grained Lennard-Jones type models are used to study the larger scale mechanisms and structures obtained due to the induced damages. We show that the response of the material to radiation damage depends on factors such as energy of the incident radiation, thermal properties, and molecular structure of the material.
Ravichandran, Ashwin↗
Ultrafast Melting at Metal-Semiconductor Interfaces: A Molecular Dynamics Study
Quantifying the thermodynamics of interfacial melting is important for several applications such as laser machining and designing radiation hardened electronic devices. Due to the short time and length scales that are involved in the process, molecular simulations provide an ideal path for understating the interfacial melting phenomena. In this work we investigate tungsten (W) – silicon carbide (SiC) interfaces which are relevant in modern high-power electronic devices. Classical molecular dynamics simulations along with the two-temperature model (TTM) were used to study the radiation induced melting of the interface while a neural network-based machine learning framework was used to track the transient re-crystallization process. The damage endured by the semiconductor at the interface following the radiation event is discussed in detail while the re-crystallization of the metal is described in terms of the classical nucleation theory.
Ashwin Ravichandran↗
Gasdynamic lasers and photon machines.
The basic operational highlights of CO2-N2 gasdynamic lasers (GDL's) are described. Features common to powerful gas lasers are indicated. A simplified model of the vibrational kinetics of the system is presented, and the importance of rapid expansion nozzles is shown from analytic solutions of the equations. A high-power pulsed GDL is described, along with estimations of power extraction. A closed-cycle laser is suggested, leading to a description of a photon generator/engine. Thermodynamic analysis of the closed-cycle laser illustrates in principle the possibility of direct conversion of laser energy to work.
Christiansen, W. H.↗
Making Complex Electrically Conductive Patterns on Cloth
A method for automated fabrication of flexible, electrically conductive patterns on cloth substrates has been demonstrated. Products developed using this method, or related prior methods, are instances of a technology known as 'e-textiles,' in which electrically conductive patterns ar formed in, and on, textiles. For many applications, including high-speed digital circuits, antennas, and radio frequency (RF) circuits, an e-textile method should be capable of providing high surface conductivity, tight tolerances for control of characteristic impedances, and geometrically complex conductive patterns. Unlike prior methods, the present method satisfies all three of these criteria. Typical patterns can include such circuit structures as RF transmission lines, antennas, filters, and other conductive patterns equivalent to those of conventional printed circuits. The present method overcomes the limitations of the prior methods for forming the equivalent of printed circuits on cloth. A typical fabrication process according to the present method involves selecting the appropriate conductive and non-conductive fabric layers to build the e-textile circuit. The present method uses commercially available woven conductive cloth with established surface conductivity specifications. Dielectric constant, loss tangent, and thickness are some of the parameters to be considered for the non-conductive fabric layers. The circuit design of the conductive woven fabric is secured onto a non-conductive fabric layer using sewing, embroidery, and/or adhesive means. The portion of the conductive fabric that is not part of the circuit is next cut from the desired circuit using an automated machine such as a printed-circuit-board milling machine or a laser cutting machine. Fiducials can be used to align the circuit and the cutting machine. Multilayer circuits can be built starting with the inner layer and using conductive thread to make electrical connections between layers.
Chu, Andrew↗
Micromachined Active Magnetic Regenerator for Low-Temperature Magnetic Coolers
A design of an Active Magnetic Regenerative Refrigeration (AMRR) system has been developed for space applications. It uses an innovative 3He cryogenic circulator to provide continuous remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. A critical component technology for this cooling system is a highly efficient active magnetic regenerator, which is a regenerative heat exchanger with its matrix material made of magnetic refrigerant gadolinium gallium garnet (GGG). Creare Inc. is developing a microchannel GGG regenerator with an anisotropic structured bed for high system thermal efficiency. The regenerator core consists of a stack of thin, single-crystal GGG disks alternating with thin polymer insulating layers. The insulating layers help minimize the axial conduction heat leak, since GGG has a very high thermal conductivity in the regenerator s operating temperature range. The GGG disks contain micro channels with width near 100 micrometers, which enhance the heat transfer between the circulating flow and the refrigerant bed. The unique flow configuration of the GGG plates ensures a uniform flow distribution across the plates. The main fabrication challenges for the regenerator are the machining of high-aspect-ratio microchannels in fragile, single-crystal GGG disks and fabrication and assembly of the GGG insulation layers. Feasibility demonstrations to date include use of an ultrashort- pulse laser to machine microchannels without producing unacceptable microcracking or deposition of recast material, as shown in the figure, and attachment of a thin insulation layer to a GGG disk without obstructing the flow paths. At the time of this reporting, efforts were focused on improving the laser machining process to increase machining speed and further reduce microcracking.
Chen, Weibo↗