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  • Other Sources  (1,348)
  • MECHANICAL ENGINEERING  (1,348)
  • 1990-1994  (1,345)
  • 1960-1964  (3)
  • 1
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    Evolving directions in NASA's planetary rover requirements and technology (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The evolution of NASA's planning for planetary rovers (that is robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that was developed to achieve the desired capabilities is reviewed. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. Robotic vehicles and their associated control systems, developed in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission, are described. Goals suggested at the time for such a MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions are presented. Some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible are described.
    Keywords: MECHANICAL ENGINEERING
    Type: CNES, Missions, Technologies, and Design of Planetary Mobile Vehicles; p 443-454
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  • 2
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    A parameter identification method for the rotordynamic coefficients of a high Reynolds number hydrostatic bearing (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Vibration and Acoustics (ISSN 0739-3717); 115; 3; p. 264-270.
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  • 3
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    Gripper for truss structure assembly (1991)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The CIRSSE two-finger gripper is designed to be used with a 6-axis wrist-mounted force-torque sensor as part of an experimental testbed for cooperative robotic manipulation. The gripper system consists of a dedicated controller and a pneumatic powered gripper that is servoed in position or grasping force. The gripper also has a between fingertip light beam sensor. The major features of this new design are: high grasping force to weight ratio (25::1) and compactness (14 cm base-fingertip, 0.8 kilograms); low cost dedicated slave controller; and simple host-controller communications protocol to minimize command interpretation delay. Shared software functions between the host and the controller processor permit the host to select servo mode, servo gain-parameter values, and calibration offsets. Hidden primitive self-test, calibration and servo confidence functions are included.
    Keywords: MECHANICAL ENGINEERING
    Type: Cooperative Intelligent Robotics in Space; Nov 06, 1990 - Nov 07, 1990; Boston, MA; United States
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  • 4
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    A walking prescription for statically-stable walkers based on walker/terrain interaction (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The walker/terrain interaction phenomena for the control of a statically stable walking machine are described. The algorithms, measures, and knowledge of walker/terrain interaction phenomena are then combined to form a prescription for how to walk on general terrain. This prescription consists of two parts: nominal control and reactive control. The function of nominal control is the evaluation and execution of planned motions, based on predicted foot force redistributions, to achieve reliable locomotion. The function of reactive control is the monitoring of walker/terrain interaction in real-time to detect anomalous conditions and then respond with the appropriate reflexive actions. Simulations and experiments have been used to test and verify various aspects of the walking prescription.
    Keywords: MECHANICAL ENGINEERING
    Type: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 1 (A93-35501 13-63); p. 149-156.
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  • 5
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    Active damping with a reaction mass actuator (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: This paper presents analytical and experimental results in actively damping flexible structures with reaction mass actuators. A two degree of freedom spring-mass model of a flexible structure is analyzed and the key parameters of actuator mass participation and pole-zero separation are related to the maximum damping achievable from rate feedback control. The main conclusion of the paper is that the larger the pole-zero separation the larger the amount of damping that can be imparted to a structural mode. Laboratory experiments conducted on an 8-foot truss structure support the analytical predictions.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Controls for optical systems; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-34276 13-74); p. 182-192.
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  • 6
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    Dynamics of rotating multicomponent turbomachinery systems (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The ultimate objective of turbomachinery vibration analysis is to predict both the overall, as well as component dynamic response. To accomplish this objective requires complete engine structural models, including multistages of bladed disk assemblies, flexible rotor shafts and bearings, and engine support structures and casings. In the present approach each component is analyzed as a separate structure and boundary information is exchanged at the inter-component connections. The advantage of this tactic is that even though readily available detailed component models are utilized, accurate and comprehensive system response information may be obtained. Sample problems, which include a fixed base rotating blade and a blade on a flexible rotor, are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 93-1629 , In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 5 (A93-33876 1; p. 2836-2847.
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  • 7
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    Magnetic bearings for free-piston Stirling engines (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The feasibility and efficiency of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery currently being developed for long-term space missions are assessed. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) which currently uses hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Active magnetic bearings of the attractive electromagnetic type are feasible for the RSSPC power piston. Magnetic support of the displacer assembly would require unacceptable changes to the design of the current RSSPC. However, magnetic suspension of both displacer and power piston is feasible for a relative-displacer version of the RSSPC. Magnetic suspension of the RSSPC power piston can potentially increase overall efficiency by 0.5 to 1 percent (0.1 to 0.3 efficieny points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. These advantages, however, are accompanied by a 5 percent increase in specific mass of the RSSPC.
    Keywords: MECHANICAL ENGINEERING
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.381-5.386.
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  • 8
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    Development of advanced seals for space propulsion turbomachinery (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Current activities in seals for space propulsion turbomachinery that NASA sponsors are surveyed. The overall objective is to provide the designer and researcher with the concepts and data to control seal dynamics and leakage. Included in the program are low-leakage seals, such as the brush seal, the 'ceramic rope' seal, low-leakage seals for liquid oxygen turbopumps, face seals for two phase flow, and swirl brakes for stability. Two major efforts are summarized: a seal dynamics in rotating machinery, and an effort in seal code development.
    Keywords: MECHANICAL ENGINEERING
    Type: SAE PAPER 921028 , ; 14 p.|SAE, Aerospace Atlantic Conference; Apr 07, 1992 - Apr 10, 1992; Dayton, OH; United States
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  • 9
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    Laminar flow in a recess of a hydrostatic bearing (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.
    Keywords: MECHANICAL ENGINEERING
    Type: STLE Tribology Transactions (ISSN 0569-8197); 35; 4; p. 738-743; Discussi
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  • 10
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    Robotics technology discipline (1990)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: Viewgraphs on robotics technology discipline for Space Station Freedom are presented. Topics covered include: mechanisms; sensors; systems engineering processes for integrated robotics; man/machine cooperative control; 3D-real-time machine perception; multiple arm redundancy control; manipulator control from a movable base; multi-agent reasoning; and surfacing evolution technologies.
    Keywords: MECHANICAL ENGINEERING
    Type: Technology for Space Station Evolution. Executive Summary and Overview; p 197-233
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  • 11
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    Milling dynamics. I - Attritor dynamics: Results of a cinematographic study (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The motions of grinding media and powder in an attritor canister were studied by means of filming the agitated charge and frame-by-frame scrutiny of the footage. In conjunction with auxiliary experiments, this permitted semiquantitative analysis of the milling action. In particular, the mill can be divided into several regions characterized by different balances between direct impacts and rolling/sliding of the grinding media. Simple calculations suggest that impacts are more capable of effecting mechanical alloying (MA) than are rolling or sliding events in an attritor. Powder circulation within an operating mill was also investigated. Based on the results and the accompanying analysis, concepts for improved attritor design are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 24A; 1; p. 175-185.
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  • 12
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    Comparative survey of dynamic analyses of free-piston Stirling engines (1991)
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    Publication Date: 2019-08-28
    Description: Reported dynamics analyses for evaluating the steady-state response and stability of free-piston Stirling engine (FPSE) systems are compared. Various analytical approaches are discussed to provide guidance on their salient features. Recommendations are made in the recommendations remarks for an approach which captures most of the inherent properties of the engine. Such an approach has the potential for yielding results which will closely match practical FPSE-load systems.
    Keywords: MECHANICAL ENGINEERING
    Type: IECEC ''91: Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 13
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    Stirling machine operating experience (1991)
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    Publication Date: 2019-08-28
    Description: Numerous Stirling machines have been built and operated, but the operating experience of these machines is not well known. It is important to examine this operating experience in detail, because it largely substantiates the claim that Stirling machines are capable of reliable and lengthy lives. The amount of data that exists is impressive, considering that many of the machines that have been built are developmental machines intended to show proof of concept, and were not expected to operate for any lengthy period of time. Some Stirling machines (typically free-piston machines) achieve long life through non-contact bearings, while other Stirling machines (typically kinematic) have achieved long operating lives through regular seal and bearing replacements. In addition to engine and system testing, life testing of critical components is also considered.
    Keywords: MECHANICAL ENGINEERING
    Type: IECEC ''91: Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 14
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    Magnetic bearings - State of the art (1993)
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    Publication Date: 2019-08-28
    Description: Magnetic bearings have existed for many years, at least in theory. Earnshaw's theorem, formulated in 1842, concerns stability of magnetic suspensions, and states that not all axes of a bearing can be stable without some means of active control. In Beam's widely referenced experiments, a tiny (1/64 in diameter) rotor was rotated to the astonishing speed of 800,000 rps while it was suspended in a magnetic field. Despite a long history, magnetic bearings have only begun to see practical application since about 1980. The development that finally made magnetic bearings practical was solid state electronics, enabling power supplies and controls to be reduced in size to where they are now comparable in volume to the bearings themselves. An attempt is made to document the current (1991) state of the art of magnetic bearings. The referenced papers are large drawn from two conferences publications published in 1988 and 1990 respectively.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 4 - Tribological materials and NDE (A94-12651 02-38); p. 133-148.
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  • 15
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    Comparison of GLIMPS and HFAST Stirling engine code predictions with experimental data (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Predictions from GLIMPS and HFAST design codes are compared with experimental data for the RE-1000 and SPRE free piston Stirling engines. Engine performance and available power loss predictions are compared. Differences exist between GLIMPS and HFAST loss predictions. Both codes require engine specific calibration to bring predictions and experimental data into agreement.
    Keywords: MECHANICAL ENGINEERING
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.53-5.58.
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  • 16
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    Development and performance of a three degree of freedom large motion vibration isolation mount for the KC-135 aircraft (1993)
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    Publication Date: 2019-08-28
    Description: Scientific microgravity experiments conducted on platforms such as the Soviet Mir space station and the U.S. Space Shuttle indicated that the microgravity environment is contaminated with disturbances which result in the reduction of a gravity quality, from micro-g to milli-g. This paper describes the vibration isolation technology developed by the Canadian Space Agency, the 1DOF Large Motion Isolation Mount (LMIM) and the 3DOF LMIM, for the KC-135 aircraft. The results of the developmental activity are presented, and the applicability of the approach taken to the Space Shuttle, Space Station Freedom, and the Mir space station is discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 93-0574 , ; 13 p.|AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States
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  • 17
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    Advanced Rotorcraft Transmission (ART) Program summary (1992)
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    Publication Date: 2019-08-28
    Description: The Advanced Rotorcraft Transmission (ART) Program was initiated to advance the state of the art for rotorcraft transmissions. The goal of the ART Program was to develop and demonstrate the technologies needed to reduce transmission weight by 25 pct and reduce noise by 10 dB while obtaining a 5000 hr 'mean time between failure'. The research done under the ART Program is summarized. A split path design was selected as best able to meet the program goals. Key part technologies needed for this design were identified, studied, and developed. Two of these technologies are discussed in detail: the load sharing of split path designs including the use of a compliant elastomeric torque splitter and the application of a high ratio, low pitch line velocity gear mesh. Development of an angular contact spherical roller bearing, transmission error analysis, and fretting fatigue testing are discussed. The technologies for a light weight, quiet, and reliable rotorcraft transmission were demonstrated.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 92-3365
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  • 18
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    Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump (1991)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Numerical simulations are used to model the dynamics of solid fragments in the high-pressure fuel turbopump of the Space Shuttle Main Engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME and JSME Joint Fluids Engineering Conference; Jun 23, 1991 - Jun 27, 1991; Portland, OR; United States
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  • 19
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    Application of powder densification models to the consolidation processing of composites (1991)
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    Publication Date: 2019-08-28
    Description: Unidirectional fiber reinforced metal matrix composite tapes (containing a single layer of parallel fibers) can now be produced by plasma deposition. These tapes can be stacked and subjected to a thermomechanical treatment that results in a fully dense near net shape component. The mechanisms by which this consolidation step occurs are explored, and models to predict the effect of different thermomechanical conditions (during consolidation) upon the kinetics of densification are developed. The approach is based upon a methodology developed by Ashby and others for the simpler problem of HIP of spherical powders. The complex problem is devided into six, much simpler, subproblems, and then their predicted contributions are added to densification. The initial problem decomposition is to treat the two extreme geometries encountered (contact deformation occurring between foils and shrinkage of isolated, internal pores). Deformation of these two geometries is modelled for plastic, power law creep and diffusional flow. The results are reported in the form of a densification map.
    Keywords: MECHANICAL ENGINEERING
    Type: International Conference on Composite Materials (ICCM/8); Jul 15, 1991 - Jul 19, 1991; Honolulu, HI; United States
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  • 20
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    Concurrent planning and execution for autonomous robots (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The Task Control Architecture (TCA) provides communication and coordination facilities to construct distributed, concurrent robotic systems. The use of TCA in a system that walks a legged robot through rugged terrain is described. The walking system, as originally implemented, had a sequential sense-plan-act control cycle. Utilizing TCA features for task sequencing and monitoring, the system was modified to concurrently plan and execute steps. Walking speed improved by over 30 percent, with only a relatively modest conversion effort.
    Keywords: MECHANICAL ENGINEERING
    Type: IEEE Control Systems Magazine (ISSN 0272-1708); 12; 46-50
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  • 21
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    NASA Planetary Rover Program (1991)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The NASA Planetary Rover Project was initiated in 1989. The emphasis of the work to date has been on development of autonomous navigation technology within the context of a high mobility wheeled vehicle at the JPL and an innovative legged locomotion concept at Carnegie Mellon University. The status and accomplishments of these two efforts are discussed. First, however, background information is given on the three rover types required for the Space Exploration Initiative (SEI) whose objective is a manned mission to Mars.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA, Lyndon B. Johnson Space Center, Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90); p 78-83
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  • 22
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    Ground controlled robotic assembly operations for Space Station Freedom (1991)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: A number of dextrous robotic systems and associated positioning and transportation devices are available on Space Station Freedom (SSF) to perform assembly tasks that would otherwise need to be performed by extravehicular activity (EVA) crewmembers. The currently planned operating mode for these robotic systems during the assembly phase is teleoperation by intravehicular activity (IVA) crewmembers. While this operating mode is less hazardous and expensive than manned EVA operations, and has insignificant control loop time delays, the amount of IVA time available to support telerobotic operations is much less than the anticipated requirements. Some alternative is needed to allow the robotic systems to perform useful tasks without exhausting the available IVA resources; ground control is one such alternative. The issues associated with ground control of SSF robotic systems to alleviate onboard crew time availability constraints are investigated. Key technical issues include the effect of communication time delays, the need for safe, reliable execution of remote operations, and required modifications to the SSF ground and flight system architecture. Time delay compensation techniques such as predictive displays and world model-based force reflection are addressed and collision detection and avoidance strategies to ensure the safety of the on-orbit crew, Orbiter, and SSF are described. Although more time consuming and difficult than IVA controlled teleoperations or manned EVA, ground controlled telerobotic operations offer significant benefits during the SSF assembly phase, and should be considered in assembly planning activities.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA, Lyndon B. Johnson Space Center, Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90); p 184-191
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  • 23
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    Flow diverter value and flow diversion method (1964)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: A flow diverter valve applicable to any fluid flow system requiring rapid bleed or bypass is disclosed. Examples of application of the flow diverter valve to a liquid rocket and a turbojet aircraft engine are given. Features of the valve include: (1) an independent fluid source is used to activate the flow diverter valve toward its closed position during its initial stage of travel; (2) the flow diverter port area and size is unlimited and the valve travel is unlimited; and (3) the valve housing is fabricated such that the valve can be a one step valve, a two step valve, or include as many steps as are found desirable.
    Keywords: MECHANICAL ENGINEERING
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  • 24
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    Human-like robots for space and hazardous environments (1990)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The three year goal for this NASA Senior Design team is to design and build a walking autonomous robotic rover. The rover should be capable of rough terrain crossing, traversing human made obstacles (such as stairs and doors), and moving through human and robot occupied spaces without collision. The rover is also to evidence considerable decision making ability, navigation and path planning skills. These goals came from the concept that the robot should have the abilities of both a planetary rover and a hazardous waste site scout.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-195549 , NAS 1.26:195549
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  • 25
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    Effect of out-of-roundness on the performance of a diesel engine connecting-rod bearing (1993)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: In this paper, the dynamic performance of the Ruston and Hornsby VEB diesel engine connecting-rod bearing with circular and out-of-round profiles is analyzed. The effect of cavitation is considered by using a cavitation algorithm, which mimics JFO boundary conditions. The effect of mass inertia is accounted for by solving coupled nonlinear equations of motion. The journal profiles considered are circular, elliptical, semi-elliptical, and three lobe epicycloid. The predicted journal trajectory and other performance parameters for one complete load cycle are presented for all of the out-of-round profiles and are also compared with the predictions for the circular bearing.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Tribology (ISSN 0742-4787); 115; 3; p. 538-543.
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  • 26
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    Pressure vessel burst test program - Progress paper No. 4 (1993)
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    Publication Date: 2019-08-27
    Description: A status report is presented for a program studying the characteristics of the blast waves and fragmentation caused by ruptured gas-filled pressure vessels. Experimental data trends have been derived from 14 burst pressure vessels. Attention is given to energy release in bursting, blast wave and fragmentation behavior, height of burst effects, fragment velocity vs vessel pressure, and comparative blast effects for spherical/composite vs cylindrical/steel pressure vessels.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 93-2100 , AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States|; 12 p.
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  • 27
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    Review of Rover fuel element protective coating development at Los Alamos (1991)
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    Publication Date: 2019-08-27
    Description: The Los Alamos Scientific Laboratory (LASL) entered the nuclear propulsion field in 1955 and began work on all aspects of a nuclear propulsion program with a target exhaust temperature of about 2750 K. A very extensive chemical vapor deposition coating technology for preventing catastrophic corrosion of reactor core components by the high temperature, high pressure hydrogen propellant gas was developed. Over the 17-year term of the program, more than 50,000 fuel elements were coated and evaluated. Advances in performance were achieved only through closely coupled interaction between the developing fuel element fabrication and protective coating technologies. The endurance of fuel elements in high temperature, high pressure hydrogen environment increased from several minutes at 2000 K exit gas temperature to 2 hours at 2440 K exit gas temperature in a reactor test and 10 hours at 2350 K exit gas temperature in a hot gas test. The purpose of this paper is to highlight the rationale for selection of coating materials used (NbC and ZrC), identify critical fuel element-coat interactions that had to be modified to increase system performance, and review the evolution of protective coating technology.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Space nuclear power systems; Proceedings of the 8th Symposium, Albuquerque, NM, Jan. 6-10, 1991. Pt. 3 (A93-13751 03-20); p. 1024-1036.
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    A continuum theory of a lubrication problem with solid particles (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: The governing equations for a two-dimensional lubrication problem involving the mixture of a Newtonian fluid with solid particles at an arbitrary volume fraction are developed using the theory of interacting continuua (mixture theory). The equations take the interaction between the fluid and the particles into consideration. Provision is made for the possibility of particle slippage at the boundaries. The equations are simplified assuming that the solid volume fraction varies in the sliding direction alone. Equations are solved for the velocity of the fluid phase and that of the solid phase of the mixture flow in the clearance space of an arbitrary shaped bearing. It is shown that the classical pure fluid case can be recovered as a special case of the solutions presented. Extensive numerical solutions are presented to quantify the effect of particulate solid for a number of pertinent performance parameters for both slider and journal bearings. Included in the results are discussions on the influence of particle slippage on the boundaries as well as the role of the interacting body force between the fluid and solid particles.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Applied Mechanics (ISSN 0021-8936); 60; 1; p. 48-58.
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  • 29
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    Resonant cryogenic chopper (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: An account is given of the design features, construction, and performance of a both mechanically and thermally robust, resonant cryogenic chopper operating at 4.2 K. The chopper can occult a 2.54-cm aperture at 4.5 Hz, with approximately 1-mW dissipation. The controllability of the stator and rotor magnetic fields facilitates performance optimization and the determination of any possible interference effects. Attention is given to long-term amplitude stability determinations.
    Keywords: MECHANICAL ENGINEERING
    Type: Applied Optics (ISSN 0003-6935); 31; 95-100
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  • 30
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    Liquid lubrication for space applications (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: Reviewed here is the state of the art of liquid lubrication for space applications. The areas discussed are types of liquid lubrication mechanisms, space environmental effects on lubrication, classification of lubricants, liquid lubricant additives, grease lubrication, mechanism materials, bearing anomalies and failures, lubricant supply techniques, and application types and lubricant needs for those applications.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 4 - Tribological materials and NDE (A94-12651 02-38); p. 59-92.
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    Comparison of Transmission Error Predictions with Noise Measurements for Several Spur and Helical Gears (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: Measured sound power data from eight different spur, single and double helical gear designs are compared with predictions of transmission error by the Load Distribution Program. The sound power data was taken from the recent Army-funded Advanced Rotorcraft Transmission project. Tests were conducted in the NASA gear noise rig. Results of both test data and transmission error predictions are made for each harmonic of mesh frequency at several operating conditions. In general, the transmission error predictions compare favorably with the measured noise levels.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290304 , ARL-TR-493 , E-8954 , NAS 1.15:106647 , NASA-TM-106647 , Joint Propulsion Conference; Jun 27, 1994 - Jun 29, 1994; Indianapolis, IN; United States
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  • 32
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    An emergency response mobile robot for operations in combustible atmospheres (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: A mobile, self-powered, self-contained, and remote-controlled robot is presented. The robot is capable of safely operating in a combustible atmosphere and providing information about the atmosphere to the operator. The robot includes non-sparking and non-arcing electro-mechanical and electronic components designed to prevent the robot from igniting the combustible atmosphere. The robot also includes positively pressurized enclosures that house the electromechanical and electronic components of the robot and prevent intrusion of the combustible atmosphere into the enclosures. The enclosures are interconnected such that a pressurized gas injected into any one of the enclosures is routed to all the other enclosures through the interconnections. It is preferred that one or more sealed internal channels through structures intervening between the enclosures be employed. Pressure transducers for detecting if the pressure within the enclosures falls below a predetermined level are included. The robot also has a sensing device for determining the types of combustible substances in the surrounding atmosphere, as well as the concentrations of each type of substance relative to a pre-determined lower explosive limit (LEL). In addition, the sensing device can determine the percent level of oxygen present in the surrounding atmosphere.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:NPO-19020-1-CU
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  • 33
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    A Review of Transmission Diagnostics Research at NASA Lewis Research Center (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: This paper presents a summary of the transmission diagnostics research work conducted at NASA Lewis Research Center over the last four years. In 1990, the Transmission Health and Usage Monitoring Research Team at NASA Lewis conducted a survey to determine the critical needs of the diagnostics community. Survey results indicated that experimental verification of gear and bearing fault detection methods, improved fault detection in planetary systems, and damage magnitude assessment and prognostics research were all critical to a highly reliable health and usage monitoring system. In response to this, a variety of transmission fault detection methods were applied to experimentally obtained fatigue data. Failure modes of the fatigue data include a variety of gear pitting failures, tooth wear, tooth fracture, and bearing spalling failures. Overall results indicate that, of the gear fault detection techniques, no one method can successfully detect all possible failure modes. The more successful methods need to be integrated into a single more reliable detection technique. A recently developed method, NA4, in addition to being one of the more successful gear fault detection methods, was also found to exhibit damage magnitude estimation capabilities.
    Keywords: MECHANICAL ENGINEERING
    Type: ARL-TR-599 , NASA-TM-106746 , E-9158 , NAS 1.15:106746
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  • 34
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    Adjustable reed for weaving net-shaped tailored fabrics (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: The invention is an apparatus and method for forming woven fabrics through the use of an adjustable reed. The adjustable reed has multiple groups of reed wires that guide the warp yarns. The groups of reed wires move on reed rails parallel to the warp direction. In addition, rail expanders permit the space between the reed wires to be modified and telescoping rods attached to the rail sliders can be turned to permit the reed wires to be skewed to alter the fill yarn angle. These adjustments to the reed permit simultaneous variation of fill yarn angles and fabric widths and allow these variations to be made during fabrication, without the need to halt production.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:LAR-15072-1
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  • 35
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    Comparison of Gap Elements and Contact Algorithm for 3D Contact Analysis of Spiral Bevel Gears (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Three dimensional stress analysis of spiral bevel gears in mesh using the finite element method is presented. A finite element model is generated by solving equations that identify tooth surface coordinates. Contact is simulated by the automatic generation of nonpenetration constraints. This method is compared to a finite element contact analysis conducted with gap elements.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290276 , ARL-TR-478 , E-8947 , NAS 1.15:106643 , NASA-TM-106643 , Joint Propulsion Conference; Jun 27, 1994 - Jun 29, 1994; Indianapolis, IN; United States
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  • 36
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    Vibration Signature Analysis of a Faulted Gear Transmission System (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: A comprehensive procedure in predicting faults in gear transmission systems under normal operating conditions is presented. Experimental data was obtained from a spiral bevel gear fatigue test rig at NASA Lewis Research Center. Time synchronous averaged vibration data was recorded throughout the test as the fault progressed from a small single pit to severe pitting over several teeth, and finally tooth fracture. A numerical procedure based on the Winger-Ville distribution was used to examine the time averaged vibration data. Results from the Wigner-Ville procedure are compared to results from a variety of signal analysis techniques which include time domain analysis methods and frequency analysis methods. Using photographs of the gear tooth at various stages of damage, the limitations and accuracy of the various techniques are compared and discussed. Conclusions are drawn from the comparison of the different approaches as well as the applicability of the Wigner-Ville method in predicting gear faults.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290195 , ARL-TR-475 , E-8914 , NAS 1.15:106623 , NASA-TM-106623 , Joint Propulsion Conference; Jun 27, 1994 - Jun 29, 1994; Indianapolis, IN; United States
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  • 37
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    Surface Fatigue Life of High Temperature Gear Materials (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Three high temperature gear materials were evaluated using spur gear surface fatigue tests. These materials were, VASCO max 350, VASCO matrix 2, and nitralloy N and were evaluated for possible use in high temperature gear applications. The fatigue life of the three high temperature gear materials were compared with the life of the standard AISI 9310 aircraft gear material. Surface fatigue tests were conducted at a lubricant inlet temperature of 321 K (120 F), a lubricant outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), a speed of 10,000 rpm, and with a synthetic paraffinic lubricant. The life of the nitralloy N was approximately the same as the AISI 9310, the life of the VASCO max 350 was much less than the AISI 9310 while the life of the VASCO matrix 2 was several times the life of the AISI 9310. The VASCO max 350 also showed very low fracture toughness with approximately half of the gears failed by tooth fracture through the fatigue spall. The VASCO matrix 2 had approximately 10-percent fracture failure through the fatigue spalls indicating moderate to good fracture toughness.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290160 , ARL-TR-401 , E-8738 , NAS 1.15:106562 , NASA-TM-106562 , Joint Propulsion Conference; Jun 27, 1994 - Jun 29, 1994; Indianapolis, IN; United States
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  • 38
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    Three-D CFD Analysis of Hydrostatic Bearings (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: The hydrostatic bearing promises life and speed characteristics currently unachievable with rolling element bearings alone. In order to achieve the speed and life requirements of the next generation of rocket engines, turbopump manufacturers are proposing hydrostatic bearings to be used in place of, or in series with, rolling element bearings. The design of a hydrostatic bearing is dependent on accurate pressure in the bearing. The stiffness and damping of the hydrostatic bearing is very sensitive to the bearing recess pressure ratio. In the conventional approach, usually ad hoc assumptions were made in determining the bearing pressure of this approach is inherently incorrect. In the present paper, a more elaborate approach to obtain bearing pressure is used. The bearing pressure and complete flow features of the bearing are directly computed by solving the complete 3-D Navier Stokes equation. The code used in the present calculation is a modified version of REACT3D code. Several calculations have been performed for the hydrostatic bearing designed and tested at Texas A&M. Good agreement has been obtained between computed and test results. Detailed flow features in the bearing will also be described and discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Marshall Space Flight Center, Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 1; p 37-55
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  • 39
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    Dual-latching solenoid-actuated valve assembly (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A tube-type shutoff valve is electrically positioned to its open or closed position by a concentric electromagnetic solenoid. The valve is dual latching in that the armature of the solenoid maintains the sliding tube of the valve in an open or closed position by means of permanent magnets which are effective when current is not supplied to the solenoid. The valve may also be actuated manually.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:MFS-28714-1
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  • 40
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    Base passive porosity for drag reduction (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A device for controlling drag on a ground vehicle is presented. The device consists of a porous skin mounted on the trailing surface of the ground vehicle. The porous skin may be separated from the vehicle surface by a distance of at least two times the boundary layer formed on the surface. Alternately, the trailing surface of the ground vehicle may be porous. The device minimizes the strength of the separation in the base and wake regions of the ground vehicle, thus reducing drag.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:LAR-15246-1
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  • 41
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    A Method for Thermal Analysis of Spiral Bevel Gears (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A modeling method for analyzing the three-dimensional thermal behavior of spiral bevel gears has been developed. The model surfaces are generated through application of differential geometry to the manufacturing process for face-milled spiral bevel gears. Contact on the gear surface is found by combining tooth contact analysis with three-dimensional Hertzian theory. The tooth contact analysis provides the principle curvatures and orientations of the two surfaces. This information is then used directly in the Hertzian analysis to find the contact size and maximum pressure. Heat generation during meshing is determined as a function of the applied load, sliding velocity, and coefficient of friction. Each of these factors change as the point of contact changes during meshing. A nonlinear finite element program was used to conduct the heat transfer analysis. This program permitted the time- and position-varying boundary conditions, found in operation, to be applied to a one-tooth model. An example model and analytical results are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A290190 , ARL-TR-457 , E-8895 , NAS 1.15:106612 , NASA-TM-106612 , 1994 International Gearing Conference; Sep 07, 1994 - Sep 09, 1994; Newcastle Upon Tyne; United Kingdom
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  • 42
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    Quick connect fastener (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A quick connect fastener and method of use is presented wherein the quick connect fastener is suitable for replacing available bolts and screws, the quick connect fastener being capable of installation by simply pushing a threaded portion of the connector into a member receptacle hole, the inventive apparatus being comprised of an externally threaded fastener having a threaded portion slidably mounted upon a stud or bolt shaft, wherein the externally threaded fastener portion is expandable by a preloaded spring member. The fastener, upon contact with the member receptacle hole, has the capacity of presenting cylindrical threads of a reduced diameter for insertion purposes and once inserted into the receiving threads of the receptacle member hole, are expandable for engagement of the receptacle hole threads forming a quick connect of the fastener and the member to be fastened, the quick connect fastener can be further secured by rotation after insertion, even to the point of locking engagement, the quick connect fastener being disengagable only by reverse rotation of the mated thread engagement.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:MFS-28829-1
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  • 43
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    Rotary blood pump (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A rotary blood pump is presented. The pump includes a pump housing for receiving a flow straightener, a rotor mounted on rotor bearings and having an inducer portion and an impeller portion, and a diffuser. The entrance angle, outlet angle, axial, and radial clearances of the blades associated with the flow straightener, inducer portion, impeller portion, and diffuser are optimized to minimize hemolysis while maintaining pump efficiency. The rotor bearing includes a bearing chamber that is filled with crosslinked blood or other bio-compatible material. A back emf integrated circuit regulates rotor operation and a microcomputer may be used to control one or more back emf integrated circuits. A plurality of magnets are disposed in each of a plurality of impeller blades with a small air gap. A stator may be axially adjusted on the pump housing to absorb bearing load and maximize pump efficiency.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:MSC-22424-1
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    Design and Experimental Performance of a Two Stage Partial Admission Turbine, Task B.1/B.4 (1992)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A three-inch mean diameter, two-stage turbine with partial admission in each stage was experimentally investigated over a range of admissions and angular orientations of admission arcs. Three configurations were tested in which first stage admission varied from 37.4 percent (10 of 29 passages open, 5 per side) to 6.9 percent (2 open, 1 per side). Corresponding second stage admissions were 45.2 percent (14 of 31 passages open, 7 per side) and 12.9 percent (4 open, 2 per side). Angular positions of the second stage admission arcs with respect to the first stage varied over a range of 70 degrees. Design and off-design efficiency and flow characteristics for the three configurations are presented. The results indicated that peak efficiency and the corresponding isentropic velocity ratio decreased as the arcs of admission were decreased. Both efficiency and flow characteristics were sensitive to the second stage nozzle orientation angles.
    Keywords: MECHANICAL ENGINEERING
    Type: AD-A277095 , NASA-CR-179548 , NAS 1.26:179548 , RI/RD92-214 , E-8833
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  • 45
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    Mechanical energy absorber (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: An energy absorbing system for controlling the force where a moving object engages a stationary stop and where the system utilized telescopic tubular members, energy absorbing diaphragm elements, force regulating disc springs, and a return spring to return the telescoping member to its start position after stroking is presented. The energy absorbing system has frusto-conical diaphragm elements frictionally engaging the shaft and are opposed by a force regulating set of disc springs. In principle, this force feedback mechanism serves to keep the stroking load at a reasonable level even if the friction coefficient increases greatly. This force feedback device also serves to desensitize the singular and combined effects of manufacturing tolerances, sliding surface wear, temperature changes, dynamic effects, and lubricity.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:MSC-22111-1
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  • 46
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    Joining of materials with engineered interlayers (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-08-14
    Description: A reliable method to join a variety of different materials is developed which uses engineered coatings to produce strong bonds by solid-state techniques at low temperatures (300-400 C). The strong bonds are capable of accommodating the strains created between Si and most substrates due to differences in thermal expansion coefficients. The approach encompasses two phases: noble metal compliant interlayers and functionally gradient interlayer bonding. Preliminary results are presented and the Ag interlayer bonds are microstructurally characterized confirming that the planar magnetron sputtered coatings/bonds are fully dense and metallurgically sound.
    Keywords: MECHANICAL ENGINEERING
    Type: ; : Review of progress
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  • 47
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    Dynamics of Multistage Gear Transmission with Effects of Gearbox Vibrations (1990)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: A comprehensive approach is presented in analyzing the dynamic behavior of multistage gear transmission systems with the effects of gearbox induced vibrations and mass imbalances of the rotor. The modal method, with undamped frequencies and planar mode shapes, is used to reduce the degrees of freedom of the gear system for time-transient dynamic analysis. Both the lateral and torsional vibration modes of each rotor-bearing-gear stage as well as the interstage vibrational characteristics are coupled together through localized gear mesh tooth interactions. In addition, gearbox vibrations are also coupled to the rotor-bearing-gear system dynamics through bearing support forces between the rotor and the gearbox. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domains to develop interpretations of the overall modal dynamic characteristics under various operating conditions. A typical three-stage geared system is used as an example. Effects of mass imbalance and gearbox vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-103109 , E-5433 , NAS 1.15:103109 , AVSCOM-TR-89-C-022 , AD-A227151 , CSME Mechanical Engineering Forum; Jun 03, 1990 - Jun 09, 1990; Toronto, Ontario; Canada
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  • 48
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    Parametric study in weld mismatch of longitudinally welded SSME HPFTP inlet (1991)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Welded joints are an essential part of pressure vessels such as the Space Shuttle Main Engine (SSME) Turbopumps. Defects produced in the welding process can be detrimental to weld performance. Recently, review of the SSME high pressure fuel turbopump (HPFTP) titanium inlet x rays revealed several weld discrepancies such as penetrameter density issues, film processing discrepancies, weld width discrepancies, porosity, lack of fusion, and weld offsets. Currently, the sensitivity of welded structures to defects is of concern. From a fatigue standpoint, weld offset may have a serious effect since local yielding, in general, aggravates cyclic stress effects. Therefore, the weld offset issue is considered. Using the finite element method and mathematical formulations, parametric studies were conducted to determine the influence of weld offsets and a variation of weld widths in longitudinally welded cylindrical structures with equal wall thickness on both sides of the joint. From the study, the finite element results and theoretical solutions are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-103534 , NAS 1.15:103534
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  • 49
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    A force-controllable macro-micro manipulator and its application to medical robots (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: This paper describes an 8-degrees-of-freedom macro-micro robot. This robot is capable of performing tasks that require accurate force control, such as polishing, finishing, grinding, deburring, and cleaning. The design of the macro-micro mechanism, the control algorithms, and the hardware/software implementation of the algorithms are described in this paper. Initial experimental results are reported. In addition, this paper includes a discussion of medical surgery and the role that force control may play. We introduce a new class of robotic systems collectively called Robotic Enhancement Technology (RET). RET systems introduce the combination of robotic manipulation with human control to perform manipulation tasks beyond the individual capability of either human or machine. The RET class of robotic systems offers new challenges in mechanism design, control-law development, and man/machine interface design. We believe force-controllable mechanisms such as the macro-micro structure we have developed are a necessary part of RET. Work in progress in the area of RET systems and their application to minimally invasive surgery is presented, along with future research directions.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA, Washington, Technology 2003: The Fourth National Technology Transfer Conference and Exposition, Volume 1; p 3-16
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    Dynamic modeling of fluid transmission lines of the DSN 70-meter antennas by using a lumped parameter model (1992)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Fluid transmission lines and fittings were found to significantly affect the dynamic and steady state operation of the engineering system in which they are incorporated. Therefore, a better understanding of the operation of a system can be obtained by including the performance of the transmission lines and fittings within the system model. The most accurate model of a transmission line or fitting is obtained by using a distributed parameter model. However, a distributed parameter model tends to be very complex. This complexity can be avoided without significant loss of model accuracy by using a lumped parameter model when the length of the fluid path through the transmission line or fitting is short. This article develops a lumped parameter model for short fluid transmission lines and fittings, describes the conditions under which the model is valid, and presents the model parameters associated with the servo hydraulic system of the Deep Space Network (DSN) 70-meter antennas.
    Keywords: MECHANICAL ENGINEERING
    Type: The Telecommunications and Data Acquisition Report 42-109: January-March 1992; 162-169
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