Browse Topic: Erosion

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Direct Deposition of Nickel Abrasion Guards on to Carbon Filled Composite Rotor Blade StructuresSM-2026-VLADA-51991/27/2026
Composite materials have become widely adopted in commercial aviation, as aerospace manufacturers look to use them to drive weight reduction and improved fuel efficiency in new aircraft designs. In the case of aircraft rotary blades, the poor wear properties of these materials have necessitated the development of metal leading edge guards that can provide critical protection against erosion and impact damage during flight. Electroforming has been a leading process for the manufacture of these protective guards, with nickel parts providing excellent wear resistance that significantly extends the service life of the rotary blade assembly. Currently there has not been a focus on utilizing direct electrodeposition of metal on to carbon filled epoxy composite structures, as traditional plating-on-plastics approaches require considerable effort in surface preparation and normally do not provide adequate adhesion to the underlying structure. Alpha Metalcraft Group has been working in cooperation with aerospace suppliers in the design of an electroplating ready composite structure that would allow for direct nickel deposition, provide excellent adhesion, and significantly reduce both the time and cost for the manufacture of ready-to-assembly rotary blade structures. Test panels were constructed of commercially available prepreg materials or by resin infusion of dry fabrics that incorporated different metal containing conductive layers to allow for the direct deposition through a nickel sulfamate electrodeposition process. Different surface modification strategies were investigated to expose the metal conducting layer and thereby provide the metal-to-metal bonding surfaces required for successful electrodeposition.
Cazzaniga, Luigi
Primer, Anodic Electrodeposition for Aircraft ApplicationsAMS3144A (Current)10/17/2019
This specification establishes the requirements for a waterborne, corrosion inhibiting, chemical and solvent resistant, anodic electrodeposition epoxy primer capable of curing at 200 to 210 °F (93 to 99 °C).
AMS G8 Aerospace Organic Coatings Committee
Hybrid Ultra-Low VOC and Non-HAP Rain Erosion Coatings19AERP08_128/1/2019
Developing a rapid-curing rain erosion coating based on a unique glycidyl carbamate (GC) hybrid resin chemistry that offers rapid reactivity and adhesion combined with the erosion, flexibility, weathering and mechanical properties of polyurethane systems. Strategic Environmental Research and Development Program, Alexandria, Virginia Numerous military aircraft and shipboard surfaces, such as radomes, antennas, gun shields, wing leading edges, and helicopter blade leading edges, are coated with a specialized erosion-resistant protective coating possessing strict performance requirements. These protective coatings must provide excellent rain erosion resistance, superior mechanical properties, good adhesion to the substrate and meet a host of other metrics outlined in MIL-PRF-32239 and SAE AMS-C- 83231A. Historical protective coatings that meet these metrics are often polyurethane-based and contain large quantities of volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and isocyanates which are hazardous and may be prohibited for use in the near future under the Prohibited and Controlled Chemical List (PCCL). A drastic reduction in VOCs, HAPs, and other hazardous compounds in such coatings will lead to significant environmental and occupational safety improvements, as well as increased coating application productivity associated with reduced application and cure times.
An Experimental Study to Evaluate the Droplet Impinging Erosion Characteristics of an Icephobic, Elastic Soft Surface2019-01-19976/10/2019
Elastic soft material/surface, such as Polydimethylsiloxane (PDMS), is a perspective, useful and low-cost hydrophobic and icephobic coating. While it has been reported to have good mechanical durability, its erosion durability under the high impacting of water droplets pertinent to aircraft inflight icing phenomena has not been explored. In this study, the droplet imping erosion characteristics of an icephobic PDMS surface/material is evaluated systematically upon the dynamic impinging of water droplets at different impact velocities (~ up to 75m/s), in comparison with other state-of-the-art icephobic materials/surfaces, such as superhydrophobic surface (SHS) and slippery liquid-infused porous surface (SLIPS). Surprisingly, the contact angle (CA) of the elastic PDMS is shown to have an over 20° increase (from 105° to 128°), which represents better hydrophobicity, after the erosion test which is mainly contributed to the higher roughness of the eroded PDMS surface. As for the icephobicity evaluation, intact PDMS was found to has ultra-low ice adhesion (~8 kPa), in comparison with SHS (i.e., ~100kPa) and SLIPS (i.e., ~35kPa). PDMS also shows outstandingly stable ice adhesion during the erosion test (i.e., fluctuation only within ~4kPa) as a result of the growth of cracks on the PDMS surface and the increased surface energy.
Ma, Liqun, Zhang, Zichen, Liu, Yang, Hu, Hui
Event-Driven Simulation of Particle-Particle and Particle-Surface Collisions in Ice Crystal Icing2019-01-20146/10/2019
This paper describes an event-driven simulation tool for predicting particle-particle and particle-surface interactions in ice crystal icing (ICI). A new accretion model which is much less empirical than existing models for predicting ICI accretion is also described. Unlike previous models, the new “gouge/bounce model” (GBM) differentiates between (erosion) losses resulting from particle bounce and those resulting from particle gouging. A bounce threshold based on the tangential Stokes number is used to calculate most of the bounce loss. The GBM also predicts ejecta velocities and directions, at least approximately, which is important because most of the mixed-phase mass flux impacting a surface actually bounces off or erodes existing material in ICI, thereby increasing the mass flux downstream. The event-driven simulation tool, denoted COLLIDE, has been applied to two test cases in which accretion growth appeared to be affected by TWC in a manner beyond that which would be expected from the accumulation parameters. An existing correlation-based accretion model (CBM), modified to predict erosion dependence on particle diameter, is also implemented and applied to the test cases. COLLIDE predicted the observed accretion dependence on TWC in a least a qualitative fashion for the majority of model/test case permutations, supporting the hypothesis that collisions between backscattered and incident particles reduces erosion and thereby increases sticking efficiency as observed in experiments with larger particles. The predictions suggest scattering of incident particles by impacts with ejecta is the dominant mechanism responsible for the flux interference effect, not particle size reduction due to particle-particle collisions.
Currie, Thomas Charles
Semi-Empirical Modelling of Erosion Phenomena for Ice Crystal Icing Numerical Simulation2019-01-19676/10/2019
The aim of this work is to develop a semi-empirical model for erosion phenomena under ice crystal condition, which is one of the major phenomena for ice crystal accretion. Such a model would be able to calculate the erosion rate caused by impinging ice crystals on accreted ice layer. This model is based on Finnie [1] and Bitter [2] [3] solid/solid collision theory which assumes that metal erosion due to sand impingement is driven by two phenomena: cutting wear and deformation wear. These two phenomena are strongly dependent on the particle density, velocity and shape, as well as on the surface physical properties such as Young modulus, Poisson ratio, surface yield strength and hardness. Moreover, cutting wear is mostly driven by tangential velocity and is more effective for ductile eroded body, whereas deformation wear is driven by normal velocity and is more effective for brittle eroded body. Several researchers based their erosion modelling on these two phenomena such as Hutchings et al. [4] for deformation erosion, or Huang et al. [5] and Arabnejad et al. [6] for cutting and deformation erosion. The main work of this paper is to develop an erosion model for ice crystal impingement based on these two phenomena, and to show its capability to predict accretion shape by simulating experimental cases from the National Research Council of Canada (NRC). NRC’s Currie et al. ice crystal experiments [7] [8] realized in warm aerodynamic conditions, such as the one encountered in high icing severity areas of a turbofan engine, show accretion severity for a large range of liquid water content to total water content. In order to validate the erosion model based on solid/solid collision, this paper presents the simulation of the lower melting rate experiment. Results show fair agreement with experimental data and allow us to propose pertinent further work.
Charton, Virgile, Trontin, Pierre, Aouizerate, Gilles, Villedieu, Philippe
Erosion Wear Response of Linz-Donawitz Slag Coatings: Parametric Appraisal and Prediction Using Imperialist Competitive Algorithm and Neural Computation05-12-02-00083/14/2019
Slag, generated from basic oxygen furnace (BOF) or Linz-Donawitz (LD) converter, is one of the recyclable wastes in an integrated steel plant. The present work aims at utilization of waste LD slag to develop surface coatings by plasma spraying technique. This study reveals that LD slag can be gainfully used as a cost-effective wear-resistant coating material. A prediction model based on an artificial neural network (ANN) is also proposed to predict the erosion performance of these coatings. The 2.27% error shows that ANN successfully predicts the erosion wear rate of the coatings both within and beyond the experimental domain. In addition to it, a novel optimization algorithm called imperialist competitive algorithm (ICA) is used to obtain minimum erosion wear rate of 12.12 mg/kg. This algorithm is inspired by the imperialistic competition and has several advantages over other revolutionary algorithms like its simplicity, less computational time, and accuracy in predicting the results. A 2.39% error is noticed while comparing the erosion wear rate result of ICA with the experimental outcome.
Pati, Pravat Ranjan, Satpathy, Mantra Prasad, Satapathy, Alok
Coating Erosion Tests Help Keep Mars 2020 Rover SafeTBMG-328479/1/2018
Air Force Research Laboratory (AFRL) Wright-Patterson Air Force Base, OH
Modelling of Electrode Erosion for Prediction of Spark Plug Lifetime2018-01-01754/3/2018
A high-fidelity arc plasma simulation tool has been developed that can model arc physics coupled with electrode erosion. The arc physics is modelled using an equilibrium, resistive magneto-hydrodynamic (MHD) model. Solid electrodes are modelled using an immersed boundary method that allows for the electrodes to deform dynamically without modifying the original mesh or the underlying governing equations. First, a partial validation of the arc physics is performed by comparing arc stretch in cross-flow with experimental results across a 1.1 mm spark gap. Subsequently, the ability to model arc physics in a coupled manner with ablating electrodes is demonstrated in 2D using a 0.7 mm electrode gap with iron electrodes. The objective of this work is to illustrate modeling of coupled arc physics with eroding electrodes; a capability that will be extended for the realistic prediction of spark plug lifetimes in future work.
Breden, Douglas P., Karpatne, Anand, Raja, Laxminarayan
The Repair Design and Technology of Metal Rotor Blades for Mi Family Helicopter - The Approach with the Usage of Reverse Engineering2017-01-21559/19/2017
Polish Armed Forces are currently operating hundred helicopters belonging to Mi family. Metal fuselage is usually resistant to the battle and the human factor. Unfortunately, metal rotor blades of Mi helicopters are sensitive to operating conditions. Single blade is made from monolithic aluminum spar and mutually separated trailing sections, which are bonded to the spar. The sections are constructed of metal sandwich panels. During aggressive military operating conditions blades sections are often damaged by debonding from the spar, fatigue cracks of section skin, dents and perforations as well as erosion. The manufacturer assumed that structurally damaged sections should be exchanged. Provided repair technologies are applied only to cosmetic damages. Unfortunately, there is a limit to number repairs which prevents replacement of two neighboring sections due to the high temperature of curing cycle during the section replacement. Additionally the old technology is expensive and time-consuming. Therefore, it was necessary to develop new technologies to enable the repair of rotor blade structural damages. The article presents an approach of designing repair of rotor blades structural damages based on a reverse engineering and selected technological aspects. Description of the substantiation of repair, calculations, environmental, thermo-mechanical and fatigue research have been undertaken.
Salacinski, Michal, Broda, Piotr, Samoraj, Piotr
Simulations of Spark-Plug Transient Plasma Breakdown in Automotive Internal Combustion Engines2017-01-05633/28/2017
The arc breakdown phase in automotive spark-plugs is a sub-microsecond event that precedes the main spark event. This phase is typically characterized by strong non-equilibrium plasma phenomena with high voltage and currents. The nature of the initial breakdown phase has strong implications for the successful spark formation and the electrode erosion/lifetime. There are evidently very few studies that seek to characterize this phase in detail. The goal of this work is to investigate this non-equilibrium plasma arc breakdown phase, using high-fidelity computational modeling. We perform studies using the VizGlow non-equilibrium plasma modeling tool. During the early breakdown phase, the plasma forms thin filamentary streamers that provide the initial conductive channel across the gap. Once the streamers bridge the gap, the plasma begins to transition to a thermal arc. The redistribution of electrostatic potential across the gap during the breakdown phase causes a large electric field intensification near the cathode. This leads to significant ion bombardment on the electrode surface and fast gas heating, both of which can be attributed to electrode erosion.
Karpatne, Anand, Breden, Douglas P., Raja, Laxminarayan
RotorShield Advanced Rotor Blade Erosion Protection, Application to V-22F-0071-2015-102575/5/2015
ABSTRACT Rotorcraft operating in desert and shore environments continue to experience severe rotor blade erosion. To mitigate damage from sand and rain, rotor blade leading edges have historically been designed with a metallic abrasion strip that serves as sacrificial material to absorb the damage. Erosion of the metal abrasion strip can become a major contributor aircraft downtime and maintenance activities. Sand erosion takes place during takeoff and landing, or during ground operations where dust, sand, and other debris are lifted by the rotor downwash. Rain erosion occurs during aircraft operation in heavy rainfall. To alleviate the maintenance costs associated with rotor erosion, a number of research efforts have investigated alternative rotor blade abrasion strip treatments to develop new structures or coatings that are more resistant to erosion damage. The ONR RotorShield erosion coating system is a technology applied to the V-22 to enable extended erosion protection and achieves the goals of reduced maintenance and repair costs associated with erosion damage. The erosion coating technology is compliant with V-22 rotor blade requirements such as: weight; fatigue; ice protection system; lightning strike and aerodynamics.
Nissen, Jeffrey, Holemans, Peter, Venezia, Jonathan
Method for Predicting Erosion Due to Cavitation of Outboard-Motor2014-32-005411/11/2014
When the planing craft with outboard motor is running, cavitation occurs around the surface of propeller and lower unit of outboard motor. Cavitation has been classified under several categories by the feature and cause of occurrence. Among them, cloud cavitation and root cavitation lead to erosion damage on the surface of lower unit and propeller. To prevent from poor appearance or performance deterioration of outboard motor by erosion damage, it is important problem to predict the erosion occurrence. Currently we can predict the cavitation phenomena sufficiently, but the area of cavitation does not necessarily correspond with the area of erosion. In this study, we present the new method to predict the area of erosion due to cavitation using CFD (computer fluid dynamics) analysis. In order to evaluate the accuracy of erosion occurrence simulation, the simulation results are compared against the result of a full-scale cruising test. Comparison between simulation and experiment suggests as follows; (1)Regarding the lower unit of outboard, the area of paint peeling on the surface of lower unit due to erosion gives close agreement with the simulation result. (2)Regarding the propeller, the area of erosion with simulation is observed more widely than the experimental result. This result indicates that we predict not only cavitation occurrence but also erosion damage of the lower unit qualitatively with new method we presented. However we require further study in order to predict the erosion of propeller. We, therefore, conclude that this prediction method holds great potential as an effective tool that could be used to design new lower unit and propeller series that have an improved cavitation erosion resistance.
Watanabe, Toshio, Sakamoto, Hiroki
Finite Element Modeling of Dissimilar Metal Self-piercing Riveting Process2014-01-19824/1/2014
In present paper, the process of joining aluminum alloy 6111T4 and steel HSLA340 sheets by self-piercing riveting (SPR) is studied. The rivet material properties were obtained by inverse modeling approach. Element erosion technique was adopted in the LS-DYNA/explicit analysis for the separation of upper sheet before the rivet penetrates into lower sheet. Maximum shear strain criterion was implemented for material failure after comparing several classic fracture criteria. LS-DYNA/implicit was used for springback analysis following the explicit riveting simulation. Large compressive residual stress was observed near frequent fatigue crack initiation sites, both around vicinity of middle inner wall of rivet shank and upper 6111T4 sheet.
Huang, Li, Lasecki, John V., Guo, Haiding, Su, Xuming
Considerations on the Use of Hydrophobic, Superhydrophobic or Icephobic Coatings as a Part of the Aircraft Ice Protection System2013-01-21089/17/2013
Ice adhesion on critical aircraft surfaces is a serious potential hazard that runs the risk of causing accidents. For this reason aircraft are equipped with active ice protection systems (AIPS). AIPS increase fuel consumption and add complexity to the aircraft systems. Reducing energy consumption of the AIPS or replacing the AIPS by a Passive Ice Protection System (PIPS), could significantly reduce aircraft fuel consumption. New coatings with superhydrophobic properties have been developed to reduce water adherence to surfaces. Superhydrophobic coatings can also reduce ice adhesion on surfaces and are used as icephobic coatings. The question is whether superhydrophobic or icephobic coatings would be able to reduce the cost associated with AIPS. To address this concern, this paper reviews the current knowledge on superhydrophobic and icephobic coatings, proposes a parameter to quantify the coating hydrophobicity level and presents methods to adapt available experimental data to aircraft applications. A second important question is whether the durability of superhydrophobic coatings is adequate for aircraft applications. Most of the available coatings that can reduce AIPS power consumption show poor erosion resistance and therefore have no practical use. To help coating manufacturers develop coatings adapted to aircraft applications, aircraft erosion test guidelines are presented. Experiments have demonstrated that superhydrophobic coatings can significantly reduce AIPS power consumption; the savings depend on the hydrophobicity level of the coating. However, erosion resistance is the biggest challenge for manufacturers and designers of coatings. Superhydrophobic and icephobic coatings need to be developed to satisfy erosion requirements. Ice phobic coatings performance needs to be improved as well.
Fortin, Guy
Validation of Proposed Metrics for Two-Body Abrasion Scratch Test Analysis StandardsTBMG-156542/1/2013
Abrasion of mechanical components and fabrics by soil on Earth is typically minimized by the effects of atmosphere and water. Potentially abrasive particles lose sharp and pointed geometrical features through erosion. In environments where such erosion does not exist, such as the vacuum of the Moon, particles retain sharp geometries associated with fracturing of their parent particles by micrometeorite impacts. The relationship between hardness of the abrasive and that of the material being abraded is well understood, such that the abrasive ability of a material can be estimated as a function of the ratio of the hardness of the two interacting materials. Knowing the abrasive nature of an environment (abrasive)/construction material is crucial to designing durable equipment for use in such surroundings.
Radio Frequency Plasma Discharge Lamps for Use as Stable Calibration Light SourcesTBMG-1526612/1/2012
Stable high radiance in visible and near-ultraviolet wavelengths is desirable for radiometric calibration sources. In this work, newly available electrodeless radio-frequency (RF) driven plasma light sources were combined with research-grade, low-noise power supplies and coupled to an integrating sphere to produce a uniform radiance source. The stock light sources consist of a 28 VDC power supply, RF driver, and a resonant RF cavity. The RF cavity includes a small bulb with a fill gas that is ionized by the electric field and emits light. This assembly is known as the emitter. The RF driver supplies a source of RF energy to the emitter.
Primer, Anodic Electrodeposition for Aircraft ApplicationsAMS3144 (Historical)11/27/2012
This specification establishes the requirements for a waterborne, corrosion inhibiting, chemical and solvent resistant, anodic electrodeposition epoxy primer capable of curing at 200 to 210 °F (93 to 99 °C).
AMS G8 Aerospace Organic Coatings Committee
Transparent Ceramics for High-Energy Laser SystemsTBMG-1225512/1/2011
When a high-energy laser (HEL) beam transmits through a window material, a part of the laser energy is absorbed by the material and causes optical aberrations. This absorbed energy results in material heating in the local exposed region, changing its refractive index based on the material’s thermo-optic coefficient, thermal expansion coefficient, and stress optic coefficient. These changes result in beam distortion and loss of output power, measured as optical path distortion (OPD), which has a severe impact on system performance.
Atomic Oxygen Fluence MonitorTBMG-107498/1/2011
This innovation enables a means for actively measuring atomic oxygen fluence (accumulated atoms of atomic oxygen per area) that has impinged upon spacecraft surfaces. Telemetered data from the device provides spacecraft designers, researchers, and mission managers with real-time measurement of atomic oxygen fluence, which is useful for prediction of the durability of spacecraft materials and components.The innovation is a compact fluence measuring device that allows in-space measurement and transmittance of measured atomic oxygen fluence as a function of time based on atomic oxygen erosion yields (the erosion yield of a material is the volume of material that is oxidized per incident oxygen atom) of materials that have been measured in low Earth orbit. It has a linear electrical response to atomic oxygen fluence, and is capable of measuring high atomic oxygen fluences (up to >1022 atoms/cm2), which are representative of multi-year low-Earth orbital missions (such as the International Space Station).
Hybrid-PIC Computer Simulation of the Plasma and Erosion Processes in Hall ThrustersTBMG-84389/1/2010
HPHall software simulates and tracks the time-dependent evolution of the plasma and erosion processes in the discharge chamber and near-field plume of Hall thrusters. HPHall is an axisymmetric solver that employs a hybrid fluid/ particle-in-cell (Hybrid-PIC) numerical approach. HPHall, originally developed by MIT in 1998, was upgraded to HPHall-2 by the Polytechnic University of Madrid in 2006. The Jet Propulsion Laboratory has continued the development of HPHall-2 through upgrades to the physical models employed in the code, and the addition of entirely new ones.
Probabilistic Multi-Factor Interaction Model for Complex Material BehaviorTBMG-76113/1/2010
Complex material behavior is represented by a single equation of product form to account for interaction among the various factors. The factors are selected by the physics of the problem and the environment that the model is to represent. For example, different factors will be required for each to represent temperature, moisture, erosion, corrosion, etc. It is important that the equation represent the physics of the behavior in its entirety accurately.
Steel Primer Chamber Assemblies for Dual Initiated PyrovalvesTBMG-54227/1/2009
A solution was developed to mitigate the potential risk of ignition failures and burn-through in aluminum primer chamber assemblies on pyrovalves. This was accomplished by changing the assembly material from aluminum to steel, and reconfiguration of flame channels to provide more direct paths from initiators to boosters. With the geometric configuration of the channels changed, energy is more efficiently transferred from the initiators to the boosters. With the alloy change to steel, the initiator flame channels do not erode upon firing, eliminating the possibility of burn-through. Flight qualification tests have been successfully passed.
Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical ApplicationsTBMG-52375/1/2009
The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer’s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers.
Nano-Multiplication-Region Avalanche Photodiodes and ArraysTBMG-26513/1/2008
Nano- multiplication- region avalanche photodiodes (NAPDs), and imaging arrays of NAPDs integrated with complementary metal oxide/semiconductor (CMOS) active-pixel-sensor integrated circuitry, are being developed for applications in which there are requirements for high-sensitivity (including photoncounting) detection and imaging at wavelengths from about 250 to 950 nm. With respect to sensitivity and to such other characteristics as speed, geometric array format, radiation hardness, power demand of associated circuitry, size, weight, and robustness, NAPDs and arrays thereof are expected to be superior to prior photodetectors and arrays including CMOS active-pixel sensors (APSs), charge-coupled devices (CCDs), traditional APDs, and microchannelplate/ CCD combinations.
The Oxidation Effect in the Titanium Alloy at High Temperature2007-01-281411/28/2007
The aim of this paper is to study of oxidation effects in creep of the Ti-6Al-4V alloy, in different atmospheres (air, nitrogen and argon). The samples were treated during 24 hours at 600°C in different atmospheres The samples treated during 24 hours at 600°C and the oxidation behavior in each atmosphere was observed. The oxidation was more aggressive in air atmosphere, forming TiO2 film in the surface. The alloy was tested in creep at 600°C in argon, nitrogen and air atmospheres using 250 MPa. The behavior of creep curves shows that useful life is better in atmospheres not so oxidant.
Reis, Danieli Aparecida Pereira, de Moura Neto, Carlos, Neto, Francisco Piorino, Barboza, Miguel Justino Ribeiro, da Silva, Cosme Roberto Moreira
Increasing the Life of a Xenon-Ion Spacecraft ThrusterTBMG-243911/1/2007
A short document summarizes the redesign of a xenon-ion spacecraft thruster to increase its operational lifetime beyond a limit heretofore imposed by nonuniform ion-impact erosion of an accelerator electrode grid. A peak in the ion current density on the centerline of the thruster causes increased erosion in the center of the grid. The ion-current density in the NSTAR thruster that was the subject of this investigation was characterized by peak-to-average ratio of 2:1 and a peak-to-edge ratio of greater than 10:1. The redesign was directed toward distributing the same beam current more evenly over the entire grid and involved several modifications of the magnetic-field topography in the thruster to obtain more nearly uniform ionization. The net result of the redesign was to reduce the peak ion current density by nearly a factor of two, thereby halving the peak erosion rate and doubling the life of the thruster. (Note: NSTAR stands for NASA SEP Technology Application Readiness; SEP stands for solar electric propulsion.)
Alloys for Nozzles of Hypersonic Wind TunnelsTBMG-471610/1/2007
Alloys are being developed for nozzles of hypersonic wind tunnels to be used in testing components of future hypersonic missiles, aircraft, and space transportation systems. The nozzle components made from these alloys will be required to retain sufficient strength to withstand stresses of as much as 600 MPa at throat surface gas temperatures as high as 1,700 K while resisting erosion and oxidation by impinging hypersonic flows of air and possibly other gases. In some applications, back-side cooling or film/transpiration cooling may be used to reduce the temperature rises in nozzles. Alternatively, in some applications, nozzles may be used, without active cooling, in either of two heat-sink modes. In one mode, exposure time would be limited in order to limit the maximum temperature rise. In the other mode, denoted the self-limiting heat-sink mode, a nozzle throat would be exposed long enough to come into thermal equilibrium with the gas, and, hence, the nozzle throat material must be chosen to withstand the maximum surface gas temperature (e.g., 1,700 K) for an indefinite time.
Slot-Antenna/ Permanent-Magnet Device for Generating PlasmaTBMG-20237/1/2007
A device that includes a rectangular - waveguide / slot - antenna structure and permanent magnets has been devised as a means of generating a substantially uniform plasma over a relatively large area, using relatively low input power and a low gas flow rate. The device utilizes electron cyclotron resonance (ECR) excited by microwave power to efficiently generate plasma in a manner that is completely electrodeless in the sense that, in principle, there is no electrical contact between the plasma and the antenna. Plasmas generated by devices like this one are suitable for use as sources of ions and/or electrons for diverse material-processing applications (e.g., etching or deposition) and for ion thrusters.
Large-Area Permanent-Magnet ECR Plasma SourceTBMG-20247/1/2007
A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design — low contamination and long operational life.
Improved Oxygen-Beam Texturing of Glucose-Monitoring OpticsTBMG-106510/1/2006
An improved method has been devised for using directed, hyperthermal beams of oxygen atoms and ions to impart desired textures to the tips of polymethylmethacrylate [PMMA] optical fibers to be used in monitoring the glucose content of blood. The improved method incorporates, but goes beyond, the method described in “Texturing Blood- Glucose-Monitoring Optics Using Oxygen Beams” (LEW-17642- 1), NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 11a. The basic principle of operation of such a glucose-monitoring sensor is as follows: The textured surface of the optical fiber is coated with chemicals that interact with glucose in such a manner as to change the reflectance of the surface. Light is sent down the optical fiber and is reflected from, the textured surface. The resulting change in reflectance of the light is measured as an indication of the concentration of glucose.
Explicit Pore Pressure Material Model in Carbon-Cloth PhenolicTBMG-11997/1/2003
An explicit material model that uses predicted pressure in the pores of a carbon-cloth phenolic (CCP) composite has been developed. This model is intended to be used within a finite-element model to predict phenomena specific to CCP components of solid-fuel-rocket nozzles subjected to high operating temperatures and to mechanical stresses that can be great enough to cause structural failures. Phenomena that can be predicted with the help of this model include failures of specimens in restrained-thermal-growth (RTG) tests, pocketing erosion, and ply lifting.
Magnetic Field Would Reduce Electron Backstreaming in Ion ThrustersTBMG-14417/1/2003
The imposition of a magnetic field has been proposed as a means of reducing the electron backstreaming problem in ion thrusters.
Eroding PotentiometersTBMG-9172/1/2003
Eroding potentiometers have been devised for measuring the time-dependent positions of char fronts advancing through layers of insulating material subject to intense heating from one side. In the original application, the material layers of interest are thermal insulators in rocket motors and the heat comes from firing of the motors, but the principle of operation is equally applicable to other insulating materials subject to intense heating (e.g., ablative fire-retardant materials). Measuring the thickness decrement of propellant (in hybrid motors in particular) is another possible application of this transducer. Telemetry informs mission control of the propellant left after each burn.
Characterization of Heat-Flux-Gauge Calibration SystemTBMG-32485/1/2002
A project is underway in the Flight Loads Laboratory (FLL) at Dryden Flight Research Center to reduce the uncertainties in heat-flux measurements. The impetus for this project is provided, in part, by the observation that uncertainties in heat-flux measurements are large — often 10 to 20 percent or more. Further impetus is provided by the fact that heat-flux calibration facilities being developed at the National Institute of Standards and Technology (NIST) operate at heat fluxes well below the levels which can be achieved during high-speed flight. Thus, a heat-flux-gauge user interested in such high fluxes has only two options: (1) take the gauge manufacturer’s calibration on faith or (2) develop and understand his or her own calibration process.
Fluorinated Diamondlike Carbon CoatingsTBMG-744610/1/2001
Some experiments directed toward the development of improved hard, lubricious coating materials have involved direct fluorination of proprietary diamondlike coats on various substrates. The idea is to retain the hardness of the diamondlike material while adding surface molecular structures that impart the chemical inertness (especially resistance to erosion by atomic oxygen) and lubricity of fluorinated polymers.
Making Ion-Accelerator Grids From Ti Instead of MoTBMG-74018/1/2001
Titanium has been found to offer several advantages over molybdenum as the material used to construct electrostatic-accelerator and -screen grids for ion thrusters for spacecraft. These advantages could also be expected to extend to the manufacture of grids for ion accelerators used in scientific research and the fabrication of semiconductors.
Analysis of Heat and Fluid Flow in Blast-furnace Hearth as a Means to Increase Productivity1999-01-25268/2/1999
The cooling of the wall and bottom of a blast furnace hearth is a problem of great practical importance for the blast-furnace campaign. The aim of this paper is a review of the literature on the subject and the presentation of the results regarding the temperature distribution in the hearth refractories of a blast furnace obtained by numerical calculations and under suitable hypotheses.
Bisio, G., Rubatto, G.
Application of Tesla and Erosive Discharge for Removing of Static Charge on the Airplane’s Surface1999-01-23696/22/1999
Questions of removing of surface charge from airplane’s surface by means of Tesla RF discharge and pulsed discharge in the atmosphere are considered. Purposes of application of these discharges are discussed. Experimental schemes of application of Tesla RF discharge and pulse erosive plasma jet are considered. Preliminary experimental results on the decrease of the surface charge by means of erosive plasma jet have been obtained.
Bychkov, Vladimir L., Klimov, Anatolii I.
High-Efficiency, Long-Life Pulsed Inductive Plasma ThrustersTBMG-298871/1/1999
Improved pulsed inductive plasma accelerators are undergoing development for use as long-life thrusters for propulsion of spacecraft on interplanetary missions and for maneuvering of spacecraft in orbit around the Earth. On Earth, plasma accelerators of this type could be used to produce a variety of atomic, molecular, and plasma beams for scientific experimentation and industrial processing (especially processing of materials in the fabrication of microcircuits). The principal advantages of the developmental accelerators over older pulsed inductive plasma accelerators arise from the use of advanced solid-state electronic pulse circuits, which operate at high repetition rates (as much as a couple of kilohertz), have long operating lives (1011 shots), deliver optimally shaped pulses, and recover reflected energy.
Determining Characteristics of Wind-Borne ParticlesTBMG-320064/1/1998
A small, robust, lightweight, low-power-consumption instrumentation system has been proposed for determining the kinetic energies, masses, and other parameters of wind-borne particles. Originally intended for use in future exploration of Mars, the system might also prove useful on Earth for quantifying the erosive and penetrating characteristics of particles in sandstorms, industrial grit-blasting streams, and the like.
Prediction of Coating Durability by Chemical/Instrumental Means9807132/23/1998
A new protocol for assessing the photooxidation characteristics of high performance, exterior automotive basecoat/clearcoats appears to be both reliable and useful in predicting long term weathering performance of such systems. This has allowed quicker utilization of new technologies or process changes to the mutual benefit of vendor and customer. The protocol is based upon measuring the rate of generation of photooxidation products after accelerated weathering, by FTIR spectroscopy.
McGinness, Jim
A Study of FEP Behaviour in the Space Environment9516407/1/1995
Teflon® FEP is regularly used as thermal control film in space applications with thicknesses varying between 12.5 μm (1/2 mil) and 127 μm (5 mil). Both flight and ground simulation data indicate a gradual degradation of the thermo-optical and mechanical properties. The same FEP material also showed localised cracks, tears and losses of the mechanical integrity on Solar Max and Hubble Space Telescope Solar Array. This paper describes, based on several flight data and on-ground tests, the parameters and causes that influence the long term behaviour of this material.
Van Eesbeek, Marc, Levadou, Francois, Milintchouk, Andrei
The Effect of Stress Absorbing Layers on the Wear Behavior of Painted Plastic Substrates9508012/1/1995
Erosion damage to automotive car bodies caused by stones and small sand particles and road debris significantly affects the appearance of paint. Painted engineering plastics as well as precoated sheet steel are affected by erosion phenomenon. Erosion of painted plastic substrates results in cosmetic concerns while that on metal substrates results in cosmetic to perforation corrosion. This work describes a laboratory simulation of erosion of painted plastic substrates by small particles on various paint and substrate types. Gloss loss was used to quantitatively evaluate erosion of painted surfaces. Wear behavior of painted plastic substrates to slag sand impact was evaluated as a function of several variables including paint type (one-component melamine crosslinked (1K) vs. two-component isocyanate crosslinked (2K)), thermal history, and coating modulus. The effect of slag sand type (particle size and chemical composition) was studied. Among the parameters that influence wear behavior, the effect of chip primer is also discussed. Failure characteristics are examined and related back to physical attributes of the system. Based on this work, it is concluded that the best wear resistance (lowest gloss loss due to erosion and lowest number of gouges) is achieved with substrates topcoated with 1K paints baked at 116°C (on several types, compounded and reactor grades of varying modulus, of TPO). Adhesion promoter was flashed at room temperature (R.T.). Chip primer does not appear to have a significant effect on wear behavior, but in some instances, it helped reduce gloss loss and the number of gouges due caused by erosion. Further study of chip primer thickness effect is on resistance to erosion damage is currently being conducted.
Ryntz, Rose A., Buzdon, Branka
Thermal Property Models Applied to Re-Entry Spacecraft Materials9415846/1/1994
The durability of ceramic is limited due to chemical reactions with the atmosphere and due to sublimation. Another aspect of the ceramic composites are their non-isotropic mechanical and thermal characteristics. Models for both the erosion and the heat transport properties have been established. These models were validated by comparison with experimental results. Applications to different design problems are shown.
Schwingel, Dirk, Iffländer, Klaus
Chromium Coating, Thin, Hard, Dense DepositAMS2438 (Historical)4/1/1994
This specification covers the engineering requirements for the deposition of a thin, dense chromium on surfaces of ferrous and nonferrous alloys and the properties of the coating. Primarily for use on metallic parts for increasing abrasion resistance, preventing galling and seizing, resisting erosion, and increasing corrosion resistance. This coating is not recommended for use on magnesium or lead alloys, or on beryllium.
AMS B Finishes Processes and Fluids Committee
Corrosion Protection Measures on an All-Aluminum Body93236010/1/1993
A body shell manufactured entirely of aluminum alloys is generally regarded as being insensitive to corrosion. The following paper confirms this assessment but specific types of corrosion affecting aluminum have to be avoided. The experience on which it is based includes vehicles with aluminum components driven in the field by customers, but is mainly derived from corrosion testing on specimen components and complete vehicles performed during the course of development. The most critical type of damage occurring is contact corrosion caused by other metals and conductive plastics. If the conversion coating on the metal is unsuitable, paint adhesion is insufficient and the characteristic aluminum filiform corrosion will start to form. Corrosion in crevices and beneath accumulated dirt is also likely to occur. This paper describes suitable protective measures, and also refers to repair techniques designed to avoid corrosion.
Dietz, Roland
Use of Starch Based Blast Media for Dry Paint Stripping9326169/1/1993
In the 1980's, several processes emerged as possible replacements for chemical strippers containing methylene chloride. A viable process appears to be dry mechanical stripping using wheat starch. It is seen as promising because of its gentle treatment of aluminum alloys and composites. The process itself is reported to be operator friendly, with no fiber or primer damage even with multiple blast cycles. The media has been tested by Boeing Commercial Airplane Co. and is in production use at Beech Aircraft Corp. and Hunting Aircraft. Boeing reports that microscopic examination has shown wheat starch blasting to be smoother and less damaging to fibers compared to hand sanding. Starch blasting leaves a smooth finish on aluminum, bare or clad, and can strip aluminum skins as thin as 0.016 in. without deformation. The media is soft and forgiving and does not cause crack closure or smearing on aluminum alloys. Testing at Pauli & Griffin's facility is continuing in a joint United Airlines/Boeing/Douglas program on stripping composite substrates and should be completed this year. An approval for multiple stripping using wheat starch is expected from Boeing in the spring of 1993. Plastic media currently has a single strip approval.
Pauli, Robert A.
Development of Corrosion Resistant Brazing Sheet for Drawn Cup Type Evaporators Part I: Alloy Development9301483/1/1993
Extensive work was conducted to develop a corrosion resistant brazing sheet alloy and to apply it to a drawn cup type evaporator in automotive air conditioning system. The items to be investigated included the influence of chemical composition of the core alloy on corrosion resistance, suppression of erosion during the brazing cycle, and enhancement of the brazing sheet formability. Additional investigation was conducted to develop a new corrosion test method on the basis of better understanding of the mechanism of corrosion in the field and to evaluate the corrosion resistance of a evaporator fabricated from the new alloy. This paper, as Part 1, describes the results of alloy development from the metallurgical and electrochemical point of view.
Takeuchi, Keizo, Isobe, Yasuaki, Yamauchi, Shigenori, Shoji, Yoshifusa, Kato, Kenji, Suzuki, Yuji
Development of High Velocity Oxy-Fuel Applied Hardface Coatings Using Taguchi Technique9109212/1/1991
High Velocity Oxy-Fuel (HVOF) sprayed hardface coatings (i.e.: chromium carbide/nickel chromium) are widely used in the aircraft industry for severe wear environment. The hardface coatings have the ability to withstand different forms of wear such as abrasion, adhesion, fretting, and particle erosion. Major aircraft engine manufacturers and repair facilities use these coatings for both original engine manufacture (OEM) and for repair and overhaul of critical engine components which experience various types of wear. The objective of this study was to develop effective spray parameters for optimized coating properties using a statistical method known as Taguchi technique. The properties evaluated were coating hardness, bond strength, particle erosion, abrasive wear and microstructures. By using Taguchi Analysis the relationship between the various key parameters and coating properties can be determined.
Chon, Tuck, Kushner, Burton A., Rotolico, Anthony J.
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