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Viewing 61 to 90 of 39463
1990-02-01
Technical Paper
900791
Reece W. Murray, James E. Hillis
Since the introduction of high purity magnesium die cast alloys, AZ91D and AM60B, many examples can be given of their ability to resist corrosion and accept a variety of decorative finishes. This paper will review the common finishing options available and the requirements for their proper application to die cast parts. The finishing systems employed in a number of commercial applications, past and present, using magnesium will be described.
1990-02-01
Technical Paper
900795
D. Nardini, I. J. McGregor, A. D. Seeds
The paper describes problems and suggested solutions in use of adhesive bonding for joining aluminum structures. Different ways to model and analyse a bonded joint are presented along with discussion on various advantages and drawbacks. As an example, the modelling and experimental results of a design exercise on a vehicle front cross-member are presented. The use of detailed joint modelling in determining the influence of local joint geometry on both adhesive and metal stresses is also demonstrated.
1990-04-01
Technical Paper
901048
Fred Ching
Abstract Composite actuators for airborne systems have demonstrated up to 47% weight savings as compared to conventional (metal) actuators while satisfying all critical tests (proof, impulse and life cycling, temperature shock, vibration, burst) based on a high performance aircraft specification (F/A-18), Figure 1. In addition, the composite actuator is “jam resistant”, satisfying a survivability requirement for the Navy/Naval Weapons Center (NWC).
1990-04-01
Technical Paper
901037
Jemei Chang
The strength of glass fiber used in composite leaf springs was measured after and before the manufacturing process. From the experimental data, the Weibull distribution parameters were estimated by graphical regression, non-linear regression and maximum likelihood methods. Correlations between the experimental data and distribution functions based on different regression techniques were compared. The fibers were found to have lost approximately 30% and 25% of their original strength after the fabricating and the molding process, respectively. Additional experiments showed that the impregnation system, the wipe-off system and the creel surface contact all adversely affect the fiber strength. Fractography and the introduction of flaws on glass fiber samples confirmed that surface defects were caused by the processing and resulted in the strength loss.
1990-04-01
Technical Paper
901024
John Wooten, Arthur Weiss
Current goals for Earth-to-Orbit transportation are to reduce the cost of payloads to low earth orbit by a factor of ten compared to existing launch capabilities. This objective translates directly to all parts of the launch vehicle system but especially propulsion. Rocketdyne is meeting this challenge today by designing an engine system which can be produced at one-tenth the cost of the current Space Shuttle Main Engine. The results from this on-going effort to design and build a high reliability, low cost engine are reviewed in this paper.
1990-04-01
Technical Paper
901066
Valery V. Lazarev
A brief review of investigations in the field of advanced structural concepts and structure member with the aim of making a forecast of hypersonic and aerospace vehicle development is given. Methods of material choice for a hot and thermal protected structure is discussed. The data concerning experimental investigations of structural concepts and structure members by using large-scale models are presented.
1990-04-01
Technical Paper
901055
David F. Pickett
Nickel alkaline batteries used in spacecraft electrical power subsystems are either nickel-cadium or nickel-hydrogen. The nickel-cadmium battery has been used since the beginning of the space program, while the nickel-hydrogen battery is a relative newcomer. Both couples are still used extensively, and recent advances in each have been documented. There are advantages and disadvantages in the use of either chemistry, but the nickel-hydrogen battery appears to be more attractive for longer life and higher specific energy for payloads greater than one kilowatt.
1990-04-01
Technical Paper
901056
Stephan M. Wolanczyk, Stephen P. Vukson
Increases in Air Force satellite power requirements dictate the need to increase battery useable energy density and lifetime over current levels. This paper will summarize efforts by Wright Research and Development Center to develop sodium-sulfur technology into a practical satellite energy storage system for GEO and LEO applications.
1990-04-01
Technical Paper
901052
Robert Higgins, Ken Kruger
Abstract A variety of high energy battery types are available to design engineers, although not all are well characterized in the general literature. Most of these new systems are based on lithium anodes and are capable of energy densities as high as 700 Wh/Kg and shelf losses of less than 3% per year. Accompanying this high energy density however are other less desirable characteristics. Certain lithium systems experience voltage sag following storage. Most have at least some safety considerations during abuse. This paper presents general information on the two highest energy lithium systems, as well as one aqueous system which, while much older, is still capable of reasonably high energy densities.
1990-10-01
Technical Paper
901131
Murray A. Goldman, Stan E. Groves, James M. Sibigtroth
After the introduction to automotive electronics in the mid 1970s, microprocessor-based automotive technology matured quickly in the 1980s as semiconductor manufacturers and automotive designers learned to work together to solve ever more challenging automotive problems. As we enter the 1990s, it is clear that microprocessor technology has become an essential technology for future automotive electronics. As advances in semiconductor technology allow more functions on a single chip, issues of reduced design cycle times have become a serious challenge. This paper explores these and other problems and discusses how semiconductor and automotive manufacturers can work together to develop solutions.
1990-10-01
Technical Paper
901133
Pradeep Shah, Gregory Armstrong
Semiconductor memory has served as a driving force behind integrated circuit chip technology over the past three decades at the same time as it has revolutionized the computer, consumer electronics, and industrial electronics industries. Recent developments in low cost reprogrammable memory technologies have added new dimensions of flexibility, serviceability, customization, and intelligence to electronic subsystems. These features are of particular value to automobiles of the future. Uses of UV-erasable EPROM's, electrically erasable EEPROM's, and related Flash erasable EEPROM's are already beginning to revolutionize powertrain and embedded controller applications, and it is anticipated that they will rapidly pervade additional safety, driver information, and comfort applications in the coming decade.
1990-10-01
Technical Paper
901146
T. Jenkins, F. Phail, S. Sackman
Many of the challenges facing the automotive industry in the 1990s will be the same as those facing the semiconductor industry. Intense worldwide competition will result in manufacturing overcapacity that reduces profitability. The global marketplace will bring emerging new markets, and suppliers will struggle to keep up with the changing consumer demographics. As manufacturers, we will be challenged to maintain capable workforces while developing products for a cleaner environment and higher functionality vehicles. Suppliers will face new challenges based on higher expectations from their customers. In the semiconductor industry, product quality approaching zero DPM will be expected and achievable, not only for the mature phase of production, but also for new product introductions. The latest in advanced semiconductor technology, long a key differentiator in the business, will become available at a price to any company wishing to enter the business.
1990-10-01
Technical Paper
901145
Hajime Sasaki, Shigeki Matsue, Yukio Maehashi
The continuously increasing integration level and resultant “system-on-silicon” and customization trends in VLSI technology will have a significant impact on future automotive electronics. The microcomputer, which is the kernel semiconductor device in automotive electronics, reflects the tremds decribed above. As the VLSI integration level increases, reliability or quality issues will become more and more important, because of the increased impact of a possible device failure. This is particularly so in VLSIs for automotive electronics. In this paper, VLSI technology trends and ways for meeting reliability or quality goals will be reviewed. Also it outlines a future look at automotive electronics in the 21st century, based on a system-on-silicon microcomputer chip, in which several processor units with different functions are integrated together by ULSI technology, where more than ten million device elements are integrated within a single silicon chip with low submicron feature size.
1990-07-01
Technical Paper
901240
Philip Stark
The encapsulation of phase change materials (PCMs) into the micropores of an ordered polymer film was investigated. Paraffin wax and high density polyethylene wax were infiltrated successfully into extruded films of the ordered polymer PBZT by a solvent exchange technique to yield microcomposites with PCM levels on the order of 40 volume percent. These microcomposite films exhibit excellent mechanical stability under cyclic freeze-thaw conditions. However, their thermal energy storage capacities, as characterized by differential scanning calorimetry, decrease significantly following freeze-thaw cycling. It appears that the ultrastructure of the PBZT and the thinness of the film (which results in high cooling rates during freeze-thaw cycling) promote the retention of the amorphous form of the PCM rather than the crystalline form. Since the amorphous form of the PCM does not contribute to the latent heat of fusion, the heat storage capacity of the microcomposite is reduced.
1990-07-01
Technical Paper
901278
Hatice S. Cullingford, Steven H. Schwartzkopf
Past spacecraft life support systems have used open-loop technologies that were simple and sufficiently reliable to demonstrate the feasibility of crewed spaceflight. A critical technology area needing development in support of both long duration missions and the establishment of lunar or planetary bases is regenerative life support. The subject of this paper is an ongoing study for a conceptual design of a Lunar-Base Controlled Ecological Life Support System (LCELSS) to support a crew size ranging from 4 to 100. An initial description of the LCELSS subsystems is provided within the framework of the conceptual design. The system design includes both plant (algae and higher plant) and animal species as potential food sources.
1990-07-01
Technical Paper
901296
H.V. Venkatasetty
Electrochemical amperometric sensors are widely used in environmental monitoring and in biomedical applications. These sensors have selectivity, fast response time, are small in size, use very low power, are easy to use and are potentially low cost. However, the conventional aqueous electrolyte based amperometric sensors have many drawbacks: they have limited operating life because of the high vapor pressure of aqueous based electrolytes, have poor baseline stability due to the build up of reaction products, and are expensive. To overcome these limitations, Honeywell has developed a new class of electrochemical gas and vapor sensors based on nonaqueous electrolytes. These sensors have a wide operating voltage, a wide operating temperature and have the potential for a long operating life. These sensors also have multigas sensing capability.
1990-07-01
Technical Paper
901305
O. Brost, P. Behrmann
A heat pipe furnace development was carried out to demonstrate the potential of the heat pipe heating technique at temperatures up to 1500°C for future material processing purposes and for process temperature control in a microgravity environment. Two different types of heat pipes were developed, viz. a variable conductance heat pipe and a specially modified constant conductance heat pipe. Both types utilizing molybdenum 41 wt% rhenium and lithium as containment material and working fluid, respectively, were successfully operated in the temperature range 900°C to 1500°C. The variable conductance heat pipe employing a gas buffering technique provides an excellent temporal temperature stability of less than 80 mK at temperatures of 1300°C and above and a very good temperature measurement accuracy by means of working fluid vapour pressure measurement.
1989-09-01
Technical Paper
892300
Michael lovene, Mark Everett
A laser cladding process has been successfully developed, qualified and implemented into production for hardfacing shrouded turbine engine blades. These nickel base superalloy hot section blades were hardfaced with a cobalt base filler metal. The process, employing dynamic powder feeding as a means of introducing filler metal to the substrate, offers significant advantages over conventional welding processes including: low heat input, limited dilution, improved metallurgical quality and uniform, near-net-shape build-ups.
1989-09-01
Technical Paper
892298
Ray Hill, Tim E. Heller
A new rapid modeling system, Optical Fabrication, uses a high-powered steered beam visible wavelength laser and low-shrink photopolymers to create model parts. The system speed and accuracy of Optical Fabrication provides new opportunities for developing composite, injection molded, or investment cast parts and developing more efficient manufacturing processes.
1989-09-01
Technical Paper
892299
M. H. McCay, T. D. McCay, N. B. Dahotre, C. M. Sharp, A. Sedghinasab, S. Gopinathan
Crack sensitive Inconel 718 was laser pulse welded using a 3.0 kW CO2 laser. Weld shape, structure and porosity were recorded as a function of the pulse duty cycle. Within the matrix studied, the welds were found to be optimized at a high (17 ms on, 7 ms off) duty cycle. These welds were superior in appearance and lack of porosity to both low duty cycle and CW welds.
1989-09-01
Technical Paper
892108
Stephen H. Roby, James A. Supp, Daniel E. Barrer, Charles H. Hogue
Base oil effects on oxidation, deposit formation, and wear in the ASTM Sequence IIID and Sequence V-D engine tests were studied. Key base oil variables were found to be base oil saturates, sulfur, nitrogen, and olefin content. No one single base oil variable adequately predicts the onset of Sequence IIID rapid viscosity increase although a linear combination of variables yielded good performance predictions. Sequence V-D deposits correlate modestly well with any of several parameters, but a four variable linear equation produces an excellent prediction model. Base oil composition was found to have no effect on valve train wear in either Sequence IIID or Sequence V-D with the additive packages used.
1989-09-01
Technical Paper
892112
J. A. McGeehan, E. S. Yamaguchi
We were able to identify engine blow-by as a primary factor affecting camshaft wear in gasoline engines. Using a 2.3-liter overhead-camshaft engine, we isolated the valve-train oil from the crankcase oil and its blow-by using a separated oil sump. We find that: with engine blow-by, the camshaft wear was high. without blow-by, the camshaft wear was low. with blow-by piped into the isolated camshaft sump, the wear was high again. Later studies identified nitric acid as a primary cause of camshaft wear. It is derived from nitrogen oxides reacting with water in the blow-by. But even in the presence of blow-by, camshaft wear can be controlled by the proper selection of zinc dithiophosphates (ZnDTP) and detergent type.
1989-09-01
Technical Paper
892111
Seppo Mikkonen, Aapo Niemi, Markku Niemi, Jorma Niskala
Excellent fuel quality or fuel detergents are required to reduce intake valve deposits in gasoline engines. However, engine oils also have a considerable effect on the deposits. In engine tests the cleanest valves were found with synthetic multigrade or mineral single grade oils, both containing no VI improvers. Popular SAE 10W-40 and 5W-50 oils formed more deposits because they contain VI improvers. Deposit weight correlated directly with oil shear stability which is a measure of the VI improver quality. Both engine oil and gasoline have to be chosen correctly for a clean intake system.
1989-09-01
Technical Paper
892113
S. W. Harris, C. T. West, T. L. Zahalka
Field tests have been run in a variety of vehicles to assess the wear and cleanliness performance of API SG (SG) compared to API SF (SF) and lower quality oils. The field tests were run in simulated delivery service with light trucks and in taxis. Oil drains and filter changes were maintained at 24,000 km to provide severe service conditions. Comparing overhead cam wear in the Sequence V-D, Sequence VE and the field demonstrated that SG quality oils have a significant margin of safety for field wear control. SG quality oils provided excellent engine cleanliness protection in the field that was significantly better than the cleanliness afforded by SF quality oils. Both SF and SG quality oils performed well in bearing wear protection. Used oil analyses were helpful for assessing the overall field performance of engine oils.
1989-09-01
Technical Paper
892095
Jeffery s. Rleck, Wilson suarez, Joseph E. Kubsh
Under certain operating conditions, automotive three-way catalysts can form hydrogen sulfide in concentrations sufficient to produce an offensive odor. Several additives from the ferrite group of compounds (M2+Fe2O4 where M = Ni, Co, Zn, Cu) have been determined to effectively reduce hydrogen sulfide emissions from three-way catalyst washcoats in laboratory tests. No alterations in the chemistry of the catalyst are required, and no detrimental effect on three-way activity is observed.
1989-09-01
Technical Paper
892210
Ric Abbott
Examples of the design concepts employed in the Beech Starship all-composite airframe are given; and the methods of material and structural cetification, including damage tolerance and adhesively bonded structures, are discussed.
1989-09-01
Technical Paper
892212
Curtis R. Davies
Abstract The increased use of composites in commercial aviation industry has created increased awareness of the effort required for development of certified structures. The certification to American and foreign regulations is complex and sometimes confusing. The regulations and certifying philosophy are still evolving in many cases. The criteria used to certify a structure has increased in complexity for certain requirements and eased in others. This is a result of the continuing use of advanced composites in commercially certified structures. While there is dispute over the extent of future advanced composite applications, it will be required on increasing amounts of commercial aviation structure. Familiarity with the procedures will be needed by all persons involved with commercial aviation. Current certification regulations and standard practices, used for compliance to those regulations, are reviewed herein.
1989-09-01
Technical Paper
892257
Michael J. Scaggs, Ulrich Sowada, Jack C. Andrellos
The present generation of industrial ultraviolet light (UV) excimer lasers are being used in a growing number of demanding production and prototype application work that had previously been beyond the capabilities of such thermal sources as CO2, operating at 10.6 μm, or Nd:YAG and Nd:Glass, operating at 1.06 μm range. The high photon energy and the very short duration of the excimer pulses can efficiently initiate photochemical and/or photothermal surface reactions leading to precision micromachining, indelible marking, and microstructure modification.
1989-09-01
Technical Paper
892254
Tibor Bornemisza, Colin Rodgers
This paper discusses the results of analytical studies supported by current development efforts and research paths to implement fast start technology for small gas turbine APU's, using non-metallic rotor components. APU start system weights can be a significant fraction of the total installed APU weight, especially if fast starts are demanded under sub-Arctic environments. It is shown that both start system weight, and rotor containment armor weight are proportional to the product of rotational speed squared and rotating assembly inertia. Significant weight savings are therefore feasible with rotating assemblies using lower density materials such as ceramics and composites. Recent tests are described at the authors affiliation wherein a modified T20 small gas turbine was accelerated from zero to 100% speed in 2 1/2 seconds.
1989-09-01
Technical Paper
892149
Edward T. King, Granger K. Chul
A 22 hour engine test was developed to evaluate the effects of fuels, lubricants, and valvetrain dynamics on the wear of OHC 2.3L engine camshafts and finger followers. Procedures include a break-in to improve test repeatability and a test sequence to allow single-shift operation. A surface analyzer capable of measuring cam lobe wear profiles to micro-inch accuracy provided a quantitative wear comparison. A pure mineral oil, as expected, resulted in higher camshaft wear than using a fully formulated SF lubricant. Cam and follower wear increased significantly when ethanol replaced gasoline as fuel. The combination of ethanol, mineral oil and heavy duty valve springs was selected to increase test severity for hardware discrimination. The average wear of the intake lobes was greater than the exhausts. Kinematic analysis and visual inspection of the valve train mechanism revealed differences in the relative motion and contact stress pattern.
Viewing 61 to 90 of 39463

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