N91-12059# Deutsche Forschungsanstalt fuer Luft- und Raumfahrt, Goettingen (Germany, F.R.). Abt. Instabilitaeten und Abloesung. A MATHEMATICAL-PHYSICAL MODEL FOR DESCRIBING TRANSITIONAL BOUNDARY LAYER FLOWS. VOLUME 1: THE LINEAR AND NONLINEAR DISTURBANCE DIFFERENTIAL EQUATIONS Thomas M. Fischer Mar. 1990 69 p In GERMAN; ENGLISH summary Report will also be announced as translation (ESA-TT-1242) (DLR-FB-90-24-Vol-1; ISSN-0171-1342; ETN-90-98046) Copyright Avail: NTIS HC/MF A04; DLR, VB-PL-DO, Postfach 90 60 58, 5000 Cologne, Fed. Republic of Germany, HC 28 Deutsche marks The linear and nonlinear disturbance differential equations which depict the stability of locally parallel, 2-D and 3-D boundary layer flows are analyzed. The spectrum of the linear operator as well as the asymptotic behavior of periodic solutions of the nonlinear system in the vicinity of the critical Reynolds number are investigated. A Landau equation, coupled with an inhomogeneous heat equation, is obtained for determining the amplitude of the disturbance and the nonlinear distortion of the mean flow. As an example, stationary perturbations in 3-D boundary layers due to the crossflow instability are considered. 35 INSTRUMENTATION AND PHOTOGRAPHY ESA A device and method are disclosed in the patent application for providing an accurate output from a unit, such as an oscillator and/or clock providing an output indicative of frequecy and/or time. The device includes a processing section having a microprocessor that develops a model characterizing the performance of the device, including establishing predicted accuracy variations, and the model is then used to correct the unit output. An external reference is used to provide a reference input for updating the model, including updating of predicted variations of the unit, by comparison of the reference input with the unit output. The ability of the model to accurately predict the performance of the unit improves as additional updates are carried out, and this allows the interval between the updates to be lengthened and/or the overall accuracy of the device to be improved. N91-12061 Minnesota Univ., Minneapolis. INLINE PARTICLE HOLOGRAPHY APPLIED TO FLUID GRA The feasibility of a new application of particle displacement holography is investigated. This application uses photographic thresholding to optically process the information in the reconstructed image, and thus obtain the local velocity magnitudes and angles. The study consists of three main parts: development of theoretical intensity field, measurement of the intensity field to validate the theory, and experimental measurement of a natural convection flow field. To assess the viability of the technique, an analytical solution of the intensity distribution in the reconstructed image of an in-line Fraunhofer particle hologram is derived. The results of this solution are presented as surface and contour plots of the calculated intensity distribution. The primary conclusion from these predictions is that photographic thresholding alone will be limited to discerning at most twenty-five planes of two-dimensional information from a given test section. The analytical solution is validated by recording the single exposure holograms of long wires. Finally, the complete application of the technique, from start-to-finish, is demonstrated. The flow field measured is the natural convection in a horizontal annulus between concentric cylinders, at a Rayleigh number of 10,000. Neutrally buoyant particles are seeded into the fluid, and the measured particle trajectories are used to infer the fluid velocities. The first scenario consists of the two-dimensional flow in an unobstructed annulus. A second quasi-three-dimensional flow is then studied, in which three radial fins are placed along half of the test section length. Measurements are obtained in both the finned and the un-finned sections of the test section from the same holographic plate. The results of these two scenarios are compared with theoretical predictions of the fluid velocity field. Dissert. Abstr. N91-12062 Stanford Univ., CA. DYNAMICALLY TESTING OF GP B ELECTROSTATICALLY Avail: Univ. Microfilms Order No. DA9017843 Gravity Probe B (GP B) is an ongoing project to test Einstein's general theory of relativity. The objective is to detect and to measure the geodetic and frame-dragging effects exhibited by an Earth-orbiting spinning gyroscope. The general theory of relativity predicts that the first of these effects is 2.22 x 10(exp -7) deg/hr and the second is 1.43 x 10(exp -9) deg/hr. To attain the mission accuracy goal, gyroscopic precession due to Newtonian torques must not exceed 1.3 x 10(exp -11) deg/hr. The time histories of these signals is used to obtain the spin vector motion in the laboratory. This motion is used to estimate the mass unbalance and the inertia ratios of the gyroscope, and to obtain information on the coefficients of the gyroscope's higher harmonics in shape. Biases in the SQUIDS were calculated, and the spin vector trace inside the gyroscope is estimated. Techniques were developed to reliably measure the time history of the spin vector in the lab using two or three pick-up loops, using the signature of the magnetic trapped flux inside the gyroscope. Also described is the technique used to estimate the gyroscope's characteristics using precession information in the lab and in the body. Dissert. Abstr. N91-12063*# National Aeronautics and Space Administration. Langley Research Center, Hampton, VA. LASER TRANSIT ANEMOMETER MEASUREMENTS OF A JANNAF NOZZLE BASE VELOCITY FLOW FIELD William W. Hunter, Jr., C. E. Russ, Jr., and J. I. Clemmons, Jr. (Vigyan Research Associates, Inc., Hampton, VA.) Aug. 1990 26 p (NASA-TM-102725; NAS 1.15:102725) Avail: NTIS HC/MF A03 CSCL 14B Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle. Author in part by AIAA (NASA-TM-103646; E-5828; NAS 1.15:103646; AIAA-91-0284) Avail: NTIS HC/MF A02 CSCL 14B Momentum transfer from high velocity nitrogen gas flow to liquid-nitrogen jets was investigated. A correlation of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for cryogenic liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied by using three differently sized two-fluid fuel atomizers with different nozzle diameters. Author N91-12065# Argonne National Lab., IL. Electron Microscopy Center for Materials Research. EVOLUTIONARY DEVELOPMENTS IN X RAY AND ELECTRON ENERGY LOSS MICROANALYSIS INSTRUMENTATION FOR THE ANALYTICAL ELECTRON MICROSCOPE Nester J. Zaluzec 1990 11 p Presented at the 12th International Congress for Electron Microscopy, Seattle, WA, 12-18 Aug. 1990 (Contract W-31-109-eng-38) (DE90-017799; CONF-900877-6) Avail: NTIS HC/MF A03 Developments in instrumentation for both X ray Dispersive and Electron Energy Loss Spectroscopy (XEDS/EELS) over the last ten years have given the experimentalist a greatly enhanced set of analytical tools for characterization. Microanalysts have waited for nearly two decades now in the hope of getting a true analytical microscope and the development of 300 to 400 kV instruments should have allowed us to attain this goal. Unfortunately, this has not generally been the case. While there have been some major improvements in the techniques, there has also been some devolution in the modern AEM (Analytical Electron Microscope). In XEDS, the majority of today's instruments are still plagued by the hole count effect, which was first described in detail over fifteen years ago. The magnitude of this problem can still reach the 20 percent level for medium atomic number species in a conventional off-the-shelf intermediate voltage AEM. This is an absurd situation and the manufacturers should be severely criticized. Part of the blame, however, also rests on the AEM community for not having come up with a universally agreed upon standard test procedure. Fortunately, such a test procedure is in the early stages of refinement. The proposed test specimen consists of an evaporated Cr film approx. 500 to 1000A thick supported upon a 3mm diameter Molybdenum 200 micron aperture. DOE N91-12066# Wyoming Univ., Laramie. Dept. of Chemistry. (AD-A224681; AFIT/CI/CIA-90-017D) Avail: NTIS HC/MF A06 CSCL 14/2 The quartz crystal microbalance (QCM) is emerging as a powerful new tool in sensor technology. In the course of this work, the QCM is used to study solvent and ion transport in poly(vinyl chloride) (PVC) ion-selective electrode (ISE) membranes and as a base for thin film analytical sensors for specific ionic species in solution. Thin (approximately 1.5 micrometer) PVC-based ISE membranes swell in solution due to solvent and/or ion uptake, the resultant mass change in the film causes the resonant frequency of the quartz crystal to decrease. The frequency measurements obtained when exposing ISE-type membranes containing neutral carrier type ionophores to analyte-containing solutions allow one to approximate the mass of solvent and analyte ions that entered the films during sensor operation. N91-12067# Michigan Univ., Ann Arbor. GRA MULTIPURPOSE 2000 C FURNACE FOR PHYSICAL TESTING IN CONTROLLED ATMOSPHERE Final Report, 1 Nov. 1988 31 Oct. 1989 I-Wei Chen 5 Feb. 1990 2 p (Grant AF-AFOSR-0127-89; AF Proj. 3842) (AD-A224851; USMC-89-C-AF-1; AFOSR-90-0831TR) Avail: NTIS HC/MF A01 CSCL 13/1 A high temperature (2000 C) furnace and a servohydraulic test EFFECTS OF TIP-BROADENING AND ASYMMETRY ON Eric J. Snyder, Elliott A. Eklund, and R. Stanley Williams 1 Jul. 1990 16 p Submitted for publication (Contract N00014-90-J-1178) (AD-A224883) Avail: NTIS HC/MF A03 CSCL 14/3 Investigated are broadening and skewing of scanning tunneling microscope topographs caused by tip size and symmetry. Model images were generated numerically by convoluting a Gaussian response function for the tip with an idealized graphite image. Atomic scale features were retained even for a 9.4 A FWHM tip function, which demonstrated that single atom tips are not required to obtain atomic resolution topographs. Model tips with an elliptical radial cross section produced many of the familiar skewed images of graphite. Such response functions could also be used to remove the skew from an experimental topograph, and thus provide an approximation for the shape of the physical tip. GRA N91-12069# European Space Agency, Paris (France). EQUIPMENT AND METHODS EMPLOYED FOR CALIBRATION OF THE SENSORS AND MEASUREMENT LINES IN THE ATTAS FLIGHT TEST PLATFORM Rudolf Oliva and Dieter Otto (Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt, Brunswick, Germany, F.R.) Aug. 1990 93 p Transl. into ENGLISH of Einrichtungen und Verfahren zum Kalibrieren von Sensoren und Messketten im Flugversuchstraeger ATTAS (Brunswick, Fed. Republic of Germany, DFVLR), Dec. 1988 94 p Original language document was announced as N90-12007 (ESA-TT-1208; DFVLR-Mitt-89-06; ETN-90-98014) Avail: NTIS HC/MF A05 A description of installations responsible for testing and calibration are presented. The fitting of the installations and the corresponding calibration methods are described. Proposals for improving calibration installations and methods are given. ESA N91-12070# Deutsche Forschungsanstalt fuer Luft- und Raumfahrt, Brunswick (Germany, F.R.). Abt. fuer Systemtechnik und Navigation. INVESTIGATION OF THE DYNAMIC BEHAVIOR AND THE FREQUENCY RESPONSE OF THE LASER GYRO GG 1342 Helmut Niederstrasser Jan. 1990 95 p In GERMAN; ENGLISH summary Report will also be announced as translation (ESA-TT-1236) (DLR-FB-90-22; ISSN-0171-1342; ETN-90-98044) Copyright Avail: NTIS HC/MF A05; DLR, VB-PL-DO, Postfach 90 60 58, 5000 Cologne, Fed. Republic of Germany, HC 33 Deutsche marks The dynamic behavior of a laser gyro under angular vibrations and constant angular rates on a single axis test table is investigated. The frequency response was studied and the measurement rate was described by power spectral densities. The hybrid angular velocity reference system was composed of an inductosyn, a tachometer and a linear accelerometer. The measurement characteristics were discussed including the measurement noise and the disorder reaction notion. The adaptability of a laser gyro to inertial navigation and flight control is demonstrated. ESA Yansun Xu 1990 164 P Avail: Univ. Microfilms Order No. DA9028119 A theoretical exploration of the characteristics and operational requirements of far-infrared and sub-millimeter wavelength metal-grating free-electron lasers is presented. In the device an open planar type of quasi-optical resonator is loaded with a strip of rectangular metal-grating, and driven by a moderate energy electron beam. The basic tuning features and energy storage capacity of the resonator are described by the dispersion relation of the periodic slow-wave structure. To give a complete description of electron and wave dynamics in the laser oscillator, a set of self-consistent equations are derived through the use of the Lorentz force equation and the Maxwell's equations. Small signal gain and output efficiency of the device are developed from the self-consistent model. The nonlinear saturation is examined with a strong-field technique which is based upon a simple nonlinear ordinary differential equation of Duffing type. A detailed evaluation of the start-current, optimum interaction length, and output efficiency of the laser oscillator at far-infrared and sub-millimeter wavelength region, indicates that the operations at wavelengths from 1 mm to 100 microns could be optimized at the output efficiencies around 1 percent with the use of a 100 keV to 1 MeV electron beam of current densities from 10 to 100(A/sq cm) and a 10 to 20 cm long grating section. A theory of klystron type metal-grating free electron lasers is also developed. Results of the proof-of-principle tests in the lower-millimeter wavelength region show that the klystron type devices generate more coherent radiations with start-current below 0.5A, output power and efficiency up to 600 watts, and 2 percent at about 35 GHz. Dissert. Abstr. N91-12073# Sandia National Labs., Albuquerque, NM. SIMPLIFIED VELOCITY INTERFEROMETER SYSTEM FOR ANY REFLECTOR (VISAR) SYSTEM W. C. Sweatt, P. L. Stanton, and O. B. Crump, Jr. 1990 12 p Presented at the SPIE's International Symposium on Optical and Optoelectronic Applied Science and Engineering Exhibit, San Diego, CA, 8-13 Jul. 1990 (Contract DE-AC04-76DP-00789) (DE91-000024; SAND-90-2419C; CONF-900756-43) Avail: NTIS HC/MF A03 A simplified, rugged VISAR (Velocity Interferometer System for Any Reflector) system was developed using a nonremovable delay element and an essentially nonadjustable interferometer cavity. In this system, the critical interference adjustments are performed during fabrication of the cavity, freeing the user from this task. Prototype systems are easy to use and give extremely high quality results. DOE (DE91-000235; LA-UR-90-3138; CONF-9009166-5) Avail: NTIS HC/MF A03 Characteristics of the harmonic emission from free electron lasers (FELS) are examined in the spontaneous, coherent-spontaneous and stimulated emission regimes. The radiation at both odd and even harmonic frequencies is treated for electron beams with finite emittance and energy spread. In the spontaneous emission regime, the transverse radiation patterns including the transverse frequency dependences, are given. How this expression is modified to include energy spread and emittance is described. In the coherent-spontaneous emission and stimulated emission regimes, the interaction of the radiation fields with the electrons must be treated self consistently. Here, a single frequency distributed transverse source function for each electron is used in the harmonic version of the 3-D code FELEX to model the harmonic radiation. The code has recently been modified to simultaneously model the fundamental and harmonic interactions for multiple-pass oscillator simulations. These modifications facilitate the examination of FELS under various operating conditions. When the FEL is lasing at the fundamental, the evolution of the harmonic fields can be examined. This evolution is unique in the sense that the electron beam radiates at the harmonic frequencies in the presence of the harmonic radiation circulating in the cavity. As a result, enhancements of the harmonic emission can be observed. Finally, harmonic lasing can occur in cases where there is sufficient gain to overcome cavity losses and lasing at the fundamental can be suppressed. The characteristics and efficiency of these interactions are explored. DOE S. C. Wilks, J. M. Dawson, and W. B. Mori (California Univ., Los Angeles.) 4 Jun. 1990 21 p Presented at the Topical Conference on Research Trends in Nonlinear and Relativistic Effects in Plasmas, LaJolla, CA, 6-9 Feb. 1990 Submitted for publication (Contract W-7405-eng-48) (DE91-000411; UCRL-JC-104417; CONF-900264-8) Avail: NTIS HC/MF A03 We discuss various novel methods of frequency upshifting short (less than or equal to 1 picosecond) pulses of laser light. All of these methods make use of either the sudden creation of a plasma or relativistic plasma waves. The first method discussed is known as photon acceleration. This method makes use of the fact that a laser pulse moving in a plasma can be thought of as a packet of photons, each possessing an effective mass of m(sub gamma) h omega(sub pe)/c squared and moving with the group velocity of the laser pulse. These photons experience a force acting on them when in the presence of a gradient in the plasma density. By using a relativistic plasma wave (i.e., a moving density gradient) traveling with the photons, the energy of the photons (thus the frequency) can be continuously increased. We then = discuss the sudden creation of a plasma in a region where there exists an electromagnetic wave. This results in a frequency shift of the wave. A similar method is the creation of an ionization front moving near the speed of light, whereby the interaction of this plasma front with an EM wave also results in a frequency upshift of the original wave. DOE N91-12077# Institut Franco-Allemand de Recherches, Saint-Louis (France). MULTI-COMPONENT LASER DOPPLER ANEMOMETERS WITH HIGH-FREQUENCY PULSED DIODE LASERS D. Dopheide, H. J. Pfeifer, G. Taux, and M. Faber (Physikalisch-Technische Bundesanstalt, Brunswick, Germany, F.R.) 20 Jun. 1989 16 p Presented at International Conference on Fluid Dynamic Measurement and its Application, Beijink, China, 25-28 Oct. 1989 (ISL-CO-219/89; ETN-90-98031) Avail: NTIS HC/MF A03 A concept for the simultaneous measurement of two or three velocity components in a flow by means of Laser Doppler Anemometry (LDA) using high frequency pulsed diode lasers is described. As against the known LDA techniques using continuous wave lasers, the idea of the method is to use high frequency pulsed diode lasers with pulse durations in the nanosecond range and to operate these at high repetition rates. The method offers the advantage that in pulse operation the optical transmitting power is increased and that, owing to sequential and phase synchronized pulsing of the diode lasers on the transmitting side of multicomponent LDAs, three velocity components can be simultaneously measured in a very elegant way with only one photodetector on the receiving side; moreover, a single wavelength suffices for all three channels. Another decisive advantage of a new method for electronic signal evaluation (coherent sampling) is that coincident measurement of the velocity components requires only a single electronic signal processing for all three channels. ESA N91-12078# Institut Franco-Allemand de Recherches, Saint-Louis (France). THE INFLUENCE OF THE COMPARISON ACCURACY IN 17 P H. J. Pfeifer, E. Sommer, and M. Koenig 10 Jul. 1989 Dual counter processors are by far the most frequently used data acquisition instruments in Laser Doppler Anemometry (LDA). All commercially available processors offer the possibility to select the comparison accuracy between the two counting results. By means of experimental findings with artificial signals and by theoretical considerations, the choice of this accuracy is shown to have no influence on the measuring results, at least if the signals are well separated from each other in time. ESA N91-12079# Air Force Systems Command, Wright-Patterson AFB, Yu. N. Mikhaylov, A. A. Mak, A. I. Stepanov, B. G. Malinin, and L. (AD-A225393; FTD-ID(RS)T-0408-90) Avail: NTIS HC/MF A02 CSCL 09/3 There exist solid-state lasers whose working bodies have the shape of cylinders of different diameters. But when operating in the periodic mode and with intensive cooling of the surface of the active element, a thermal lens is formed in the rod, causing the outgoing radiation to increase in divergence, which can lead to malfunctioning of the active element. The purpose of the invention is to increase the allowable repetition frequency of the radiation pulses, that is, to increase the mean laser radiation power and to narrow its radiation pattern. GRA N91-12080# Deutsche Forschungsanstalt fuer Luft- und Raumfahrt, Stuttgart (Germany, F.R.). Inst. fuer Technische Physik. LASER TECHNOLOGY FOR SPACE TASKS Uwe Brauch, Wolfgang Schall, Gerhard Spindler, Wolfram Wittwer, and Eberhard Zeyfang Apr. 1990 52 p In GERMAN; ENGLISH summary Report will also be announced as translation (ESA-TT-1246) (DLR-Mitt-90-10; ISSN-0176-7739; ETN-90-98048) Copyright Avail: NTIS HC/MF A04; DLR, VB-PL-DO, Postfach 90 60 58, 5000 Cologne, Fed. Republic of Germany, HC 20 Deutsche marks The possibilities of using lasers for energy supply, transport and debris elimination in space are studied. Laser cutting has been successful for aluminum, titanium and their alloys, and ceramics and composites, for space structures. Optimal photoelectric convectors of laser light to electric energy show a high efficiency, such as thermic lasers, which seem a good alternative to chemical and electrical energy vectors for low Earth orbital stations. For the estimation of the debris size, the focusing of a laser beam with lenses or a little mirror is possible with mean power lasers. It is concluded that laser technology shows a high potential for the future and needs a better development. ESA N91-11705*# Spectra Technology, Inc., Bellevue, WA. Rhidian Lawrence In NASA, Langley Research Center, Airborne 37 MECHANICAL ENGINEERING Includes auxiliary systems (nonpower); machine elements and processes; and mechanical equipment. N91-12081# Southwest Research Inst., San Antonio, TX. Dept. of Engine and Vehicle Research. LABORATORY EVALUATIONS OF CONTROLLED COMBUSTION QUENCHING AND STRATIFIED EXHAUST GAS INJECTION FOR NOX CONTROL ON A FOUR-STROKE RECIPROCATING ENGINE Topical Report, May 1987 - Dec. 1988 R. H. Thring Jun. 1990 66 p (Contract GRI-5084-251-1101) (PB90-258971; SWRI-03-1781-102; GRI-90/0069) Avail: NTIS HC/MF A04 CSCL 131 The report describes laboratory evaluations of controlled combustion quenching (CCQ) and stratified exhaust gas injection (SEG), two newly proposed techniques for NO(x) control in natural gas piston engines. With CCQ a quenching fluid is injected into the combustion chamber during the combustion process. CCQ showed NO(x) reductions of 60 to 85 percent, with relatively small penalties in fuel consumption (less that 8 percent) and other emissions. Another potential advantage of CCQ is that, unlike conventional water injection, there seemed to be very little contamination of the lubrication oil. This fact suggests that CCQ may be applicable without causing engine durability degradation, such as has been feared for conventional water injection. Engine tests of stratified exhaust gas injection were not so promising in that, for a given flow rate of exhaust gas the stratified exhaust gas gave only half as much reduction in NO(x) as homogeneous exhaust gas recirculation. However, it is believed that the exhaust gas stratification was not optimally configured; that is, the exhaust GRA gas cloud was located too far from the spark plug. N91-12082 Aston Univ., Birmingham (England). FLEXIBLE HIGH-SPEED MACHINERY Ph.D. Thesis Lee Fenney 1989 240 p Avail: Univ. Microfilms Order No. BRDX89642 An investigation into methods for the design of flexible high-speed product processing machinery is described, consisting of independent electromechanically actuated machine functions which operate under software coordination and control. An analysis is made of the elements of traditionally designed cam-actuated, mechanically coupled machinery, so that the operational functions and principal performance limitations of the separate machine elements may be identified. These are then used to define the requirements for independent actuators machinery, with a discussion of how this type of design approach is more suited to modern manufacturing trends. A distributed machine controller topology is developed which is a hybrid of hierarchical and pipeline control. An analysis is made, with the aid of dynamic simulation modelling, which confirms the suitability of the controller for flexible machinery control. The simulations include complex models of multiple independent actuators systems, which enable product flow and failure analyses to be performed. An analysis is made of high performance brushless dc servomotors and their suitability for actuating machine motions is assessed. Procedures are developed for the selection of brushless servomotors for intermittent machine motions. An experimental rig is described which has enabled the actuation and control methods developed to be implemented. With reference to this, an evaluation is made of the suitability of the machine design method and a discussion is given of the developments which are necessary for operational independent actuators machinery to be attained. Dissert. Abstr. N91-12083 Sheffield Univ. (England). THEORETICAL AND EXPERIMENTAL STUDY ON THE A theoretical and experimental investigation is described of an ultrasonic fuel injector valve constructed from a tapered metal horn whose wide end is bonded to a quartz crystal. Fuel enters sideways at the longitudinal antinode and passes along a central hole to a ball valve at the tip. When the crystal is driven by an oscillatory pulse, it excites longitudinal vibrations, bounding the ball from its seat and releasing fuel. The ball motion without any liquid resistance was studied theoretically through a computer program. Parameters such as the maximum gap between the ball and the seat, the frequency, amplitude and initial condition of the tip motion, and the time of impact were studied, and compared with measurements of ball motion in a large vibrating model. The injector tip motion was measured using a laser technique. The measurements were made with and without fuel flow. The effects of the fuel supply pressure and pulse width on the tip motion were studied. Using this data, the effect of the actual (non-ideal) motion of the tip on the behavior of the ball was studied theoretically. A model of the valve was designed so that flow forces on the ball and the flow rates through the various passages could be measured. Using this data, the ball motion with fluid resistance was computed under various conditions. This in turn permitted the fluid flow from the injector valve to be predicted. Five scale models of new valve geometries were designed and installed on an improved test rig. By this means, the effect of valve geometry on flow force and the flow rates within the valve were studied. The behavior of actual injector flow during flow pulses was studied using laser anemometry. Dissert. Abstr. N91-12084 Purdue Univ., West Lafayette, IN. Avail: Univ. Microfilms Order No. DA9018787 A high performance, high speed robotic arm must be able to manipulate objects with a high degree of accuracy, repeatability and dexterity. As with any other physical system, there are a number of factors causing uncertainties in the behavior of a robotic manipulator. These factors include manufacturing and assembling tolerances, and errors in the joint actuators and controllers. In order to study the effect of these uncertainties on the robotic end-effector and to obtain a better insight into the manipulator behavior, the concepts of theory of probability are applied to the manipulator kinematics and dynamics. Based on these probabilistic models, kinematic and dynamic performance criteria are defined to provide a measure of the behavior of the robotic end-effector. Techniques are presented to compute these criteria. The effect of the tolerances on various manipulator parameters on these criteria is studied. A methodology is developed to assign the tolerances optimally, that maximizes these criteria subject to constraints on the manipulator cost. Results show that very significant and cost effective improvements can be achieved in the manipulator performance with the use of optimal tolerances. Another desirable property of a robotic arm is the degree of dexterity with which it can manipulate objects. This aspect of the manipulator performance is investigated, and new criteria are proposed to provide a measure of the kinematic, dynamic, and force manipulating abilities. It is shown that optimization of these criteria can lead to significant improvements in the overall manipulating capabilities of a robotic arm. Numerical illustrations are presented throughout this dissertation using a two-link planar manipulator and the Stanford Dissert. Abstr. arm. N91-12085 Michigan State Univ., East Lansing. Jinsiang Shaw 1989 142 p Avail: Univ. Microfilms Order No. DA9018745 The non-linear dynamic behavior of symmetric rotors is investigated using methods from dynamical systems and bifurcation theories. Rotordynamic instabilities and resonances caused by internal hysteresis, fluid film bearing forces, and mass unbalance are analyzed. A slender, flexible shaft made of a viscoelastic material and rotating at a constant rate about its longitudinal axis is used to study the effects of internal hysteresis and mass unbalance on rotordynamics. An unbalanced disk mounted midway between two supporting fluid film journal bearings on a rigid shaft is used to examine the effects of fluid bearing forces and mass unbalance. For the flexible shaft model, internal damping can cause an instability at a certain critical speed. The instabilities are predicted using the linearized shaft model and the post-critical behaviors are determined by applying the center manifold theory to the full non-linear equations of motion. Synchronous whirl, non-synchronous whirl, and competing-mode types of behaviors are shown possible for various ranges of the parameter values. The first vibrational mode of the shaft is then used to determine the unbalanced effect on system behavior. Special attention is paid to the interaction between the primary resonance caused by mass unbalance and the destabilizing influence of internal damping. For the second model the non-linear oscillations of a rotor supported in fluid film journal bearings are analyzed. With the introduction of periodic forcing due to rotor unbalance, the results show that the limit cycle arising from the whirl instability in the neighborhood of the threshold speed is perturbed and harmonic, subharmonic, as well as amplitude modulated responses are observed when certain resonant conditions occur. Dissert. Abstr. N91-12086 Council for National Academic Awards (England). Roberto F. de Noronha 1989 222 p The detection of transverse cracks in rotors of turbo-generator units through vibration monitoring is examined. A crack model was developed using three dimensional finite element (FE) simulations. Static analyses of how a vertical bending load affects the crack opening and the local flexibility were also performed. The 3D FE mesh was generated using IDEAS and the resulting model analyzed through ABAQUS. The results from the static analysis allowed the stiffness matrix of a rotor beam element with a transverse crack at the center to be calculated. An unbalance response program was modified to work with the cracked finite element and to solve the system of equations through step-by-step |