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At least 73 records · Page 4

Optimization applications in aircraft engine design and test

Starting with the NASA-sponsored STAEBL program, optimization methods based primarily upon the versatile program COPES/CONMIN were introduced over the past few years to a broad spectrum of engineering problems in structural optimization, engine design, engine test, and more recently, manufacturing processes. By automating design and testing processes, many repetitive and costly trade-off studies have been replaced by optimization procedures. Rather than taking engineers and designers out of the loop, optimization has, in fact, put them more in control by providing sophisticated search techniques. The ultimate decision whether to accept or reject an optimal feasible design still rests with the analyst. Feedback obtained from this decision process has been invaluable since it can be incorporated into the optimization procedure to make it more intelligent. On several occasions, optimization procedures have produced novel designs, such as the nonsymmetric placement of rotor case stiffener rings, not anticipated by engineering designers. In another case, a particularly difficult resonance contraint could not be satisfied using hand iterations for a compressor blade, when the STAEBL program was applied to the problem, a feasible solution was obtained in just two iterations.

Pratt, T. K.↗

Dynamic characteristics of the national full-scale aerodynamic complex drive fan blades

An extensive experimental test program was conducted to define the dynamic characteristics of the newly installed fan blades of the NASA Ames 40- by 80-/80- by 120-Foot Wind Tunnel. The tests were intended to substantiate the blade design and manufacturing process, verify installation integrity, and guarantee safe fan-drive operation. The program included a shake test of each fan blade after installation and before operation as well as the monitoring of blade strain levels during initial operation. Structural characteristics, as determined by the shake test, include the modal frequency and damping values for elastic bending and torsion modes between 5 and 130 Hz. Operational testing defined the maximum and oscillatory blade-bending strains throughout the drive-system operational envelope. Results are presented for the shake test and initial operation of the 40- by 80-Foot Wind Tunnel circuit.

Peterson, Randall L.↗

Software For Allocation Of Tolerances

Collection of computer programs being developed to assist engineers in allocating tolerances to dimensions of components and assemblies. System reflects tolerancing expertise of design and manufacturing engineers; helps engineers maintain comprehensive tolerancing policy and overview that might otherwise get lost when attending to details of design and manufacturing processes. Necessary to allocate tolerances for three main reasons: tolerances allow for variations in dimensions of components as manufactured; assembly of two or more components, dimensions lie between specified limits; and part replaced must fit in place.

Fernandez, Ken↗

High-Energy-Density Electrolytic Capacitors

Reductions in weight and volume make new application possible. Supercapacitors and improved ultracapacitors advanced electrolytic capacitors developed for use as electric-load-leveling devices in such applications as electric vehicle propulsion systems, portable power tools, and low-voltage pulsed power supplies. One primary advantage: offer power densities much higher than storage batteries. Capacitors used in pulse mode, with short charge and discharge times. Derived from commercially available ultracapacitors. Made of lightweight materials; incorporate electrode/electrolyte material systems capable of operation at voltages higher than previous electrode/electrolyte systems. By use of innovative designs and manufacturing processes, made in wide range of rated capacitances and in rated operating potentials ranging from few to several hundred volts.

Yen, Shiao-Ping S.↗

Introduction of laser initiation for the 48-inch Advanced Solid Rocket Motor (ASRM) test motors at Marshall Space Flight Center (MSFC)

The Advanced Solid Rocket Motor is a new design for the Space Shuttle Solid Rocket Booster. The new design will provide more thrust and more payload capability, as well as incorporating many design improvements in all facets of the design and manufacturing process. A 48-inch (diameter) test motor program is part of the ASRM development program. This program has multiple purposes for testing of propellent, insulation, nozzle characteristics, etc. An overview of the evolution of the 48-inch ASRM test motor ignition system which culminated with the implementation of a laser ignition system is presented. The laser system requirements, development, and operation configuration are reviewed in detail.

Zimmerman, Chris J.↗

Generation of precedence relations for mechanical assemblies

Planning of assembly sequences is essential to the manufacturing system design process. Several methodologies have been proposed to represent all the feasible assembly sequences. In this thesis, three algorithms are presented to generate three sets of precedence relations based on all the infeasible assembly tasks, all the infeasible assembly states, and all the feasible assembly sequences, respectively. The equivalence of the resulting sets of precedence relations to the AND/OR graph is established. A new property, the real time property, of a representation of assembly sequences is defined and discussed. A representation of assembly sequences is said to have the real time property, if it is possible to generate the next assembly task by testing locally in the representation, and it will guarantee that the generated assembly task will not lead the assembly sequence to a dead end situation, in which no feasible assembly task can be performed any more. It is shown that the correctness and completeness of one representation can not guarantee the real time property of the representation. It is proven that the directed graph representation and the set of precedence relations based on all the infeasible assembly states have the real time property, while the AND/OR graph representation and the set of precedence relations based on all the infeasible assembly tasks do not have the real time property. Finally in the thesis, the PLEIDEAS system, a PLanning Environment for Integrated DEsign of Assembly Systems, is described and illustrated by an example.

Zhang, Hui↗

NIST: Information Management in the AMRF

The information management strategies developed for the NIST Automated Manufacturing Research Facility (AMRF) - a prototype small batch manufacturing facility used for integration and measurement related standards research are outlined in this video. The five major manufacturing functions - design, process planning, off-line programming, shop floor control, and materials processing are explained and their applications demonstrated.

Callaghan, George↗

An Analytical Tool for Fracture Control

The structural integrity of critical NASA space flight hardware is ensured through a damage tolerance program which is dictated in the fracture control requirements. The goal of a fracture control program is to ensure proper material selection and control, control of working stress levels, use of fracture resistant design concepts, manufacturing process control, and the use of qualified inspection procedures. The damage tolerance philosophy assumes that all components contain initial defects and the damage accumulation process is thus entirely crack propagation. The service capability of fracture critical components is determined by analysis and/or test. A large percentage of NASA fracture critical hardware is certified by analysis only and it is therefore imperative that the analysis code utilized contain the latest state of the art technology. Not all space contractors and vendors are able to develop and maintain an analysis code which meets this requirement. A response to this need has been fulfilled by the development of the NASA/FLAGRO (NASGRO) fracture mechanics code here at the Johnson Space Center. The NASGRO code is based primarily in Linear Elastic Fracture Mechanics (LEFM) and is continually updated to meet to needs of the user community. Development assistance comes from other NASA centers as well as the European Space Agency (ESA). The code currently has a vast materials data file (over 350 different entries) which defines the material strength, fracture toughness, crack growth rate, and crack growth threshold. The code also allows for user defined inputs of data from other sources. The code also provides a large library of stress intensity factor solutions for numerous geometries and loading conditions.

Patin, Raymond M.↗

Technology Needs for Reduced Design and Manufacturing Cost of Commercial Transport Engines

The objective of the study was to assess the needs in the design and manufacturing processes and identify areas where technology could impact in cost and cycle-time reduction. At the highest level, the team first identified the goals that were in line with long-range needs of the aeropropulsion industry, and to which technology and process improvements would be required to contribute. These goals are to reduce the time and costs in the development cycle of aircraft engines by a factor of two, reduce production cycle time by a factor of four, and to reduce production costs by 25%. Also, it was the intent of the team to identify the highest impact technologies that could be developed and demonstrated in five years.

Rohn, Douglas A.↗

Thermal Structures Technology Development for Reusable Launch Vehicle Cryogenic Propellant Tanks

Analytical and experimental studies conducted at the NASA Langley Research Center for investigating integrated cryogenic propellant tank systems for a Reusable Launch Vehicle are described. The cryogenic tanks are investigated as an integrated tank system. An integrated tank system includes the tank wall, cryogenic insulation, Thermal Protection System (TPS) attachment sub-structure, and TPS. Analysis codes are used to size the thicknesses of cryogenic insulation and TPS insulation for thermal loads, and to predict tank buckling strengths at various ring frame spacings. The unique test facilities developed for the testing of cryogenic tank components are described. Testing at cryogenic and high-temperatures verifies the integrity of materials, design concepts, manufacturing processes, and thermal/structural analyses. Test specimens ranging from the element level to the subcomponent level are subjected to projected vehicle operational mechanical loads and temperatures. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of light-weight reusable cryogenic propellant tanks.

Johnson, Theodore F.↗

Assessment of the State-of-the-Art in the Design and Manufacturing of Large Composite Structure

This viewgraph presentation gives an assessment of the state-of-the-art in the design and manufacturing of large component structures, including details on the use of continuous fiber reinforced polymer matrix composites (CFRP) in commercial and military aircraft and in space launch vehicles. Project risk mitigation plans must include a building-block test approach to structural design development, manufacturing process scale-up development tests, and pre-flight ground tests to verify structural integrity. The potential benefits of composite structures justifies NASA's investment in developing the technology. Advanced composite structures technology is enabling to virtually every Aero-Space Technology Enterprise Goal.

Harris, C. E.↗

InGaAsSb Detectors' Characterization for 2-Micron CO2 Lidar/DIAL Applications

Recent interest in monitoring atmospheric CO2 focuses attention on infrared remote sensing using the 2-micron lidar/differential absorption lidar (DIAL) technique. Quantum detectors are critical components in this technique, and many research efforts concentrate on developing such devices for the 2-micron wavelength. Characterization results of InGaAsSb quantum detectors for the 2-micron wavelength range are presented, including experimental setup and procedure. Detectors are prototype devices manufactured by using separate absorption and multiplication (SAM) structures. Characterization experiments include V-I measurements, spectral response and its variation with bias voltage and temperature, noise measurements, noise-equivalent-power (NEP) and detectivity calculations, and signal-to-noise ratio (SNR) estimation. A slight increase in the output signal occurred with increased bias voltage and was associated with a noise level increase. Cooling down the detectors reduces noise and shifts the cutoff wavelength to shorter values. Further improvement in the design and manufacturing process, by increasing the device gain and lowering its noise level, is necessary to meet the required CO2 lidar/DIAL specifications.

Refaat, Tamer F.↗

InGaAsSb Detectors Characterization for 2-Micron CO2 Lidar/DIAL Applications

Recent interest in monitoring atmospheric CO2 focuses attention on infrared remote sensing using the 2-micron lidar/differential absorption lidar (DIAL) technique. Quantum detectors are critical components in this technique, and many research efforts concentrate on developing such devices for the 2-micron wavelength. Characterization results of InGaAsSb quantum detectors for the 2-micron wavelength range are presented, including experimental setup and procedure. Detectors are prototype devices manufactured by using separate absorption and multiplication (SAM) structures. Characterization experiments include V-I measurements, spectral response and its variation with bias voltage and temperature, noise measurements, noise-equivalent-power (NEP) and detectivity calculations, and signal-to-noise ratio (SNR) estimation. A slight increase in the output signal occurred with increased bias voltage and was associated with a noise level increase. Cooling down the detectors reduces noise and shifts the cutoff wavelength to shorter values. Further improvement in the design and manufacturing process, by increasing the device gain and lowering its noise level, is necessary to meet the required CO2 lidar/DIAL specifications.

Refaat, Tamer F.↗

Superfinished Surfaces for Power Transfer Systems Improvement

The continuous demands for high performance and lightweight power train systems resulted in requirements for higher power density gearing systems. However, increasing the load bearing capacity of the gear teeth, without increasing size, places stringent requirements upon metallurgy, dimensional control, and surface finish of the final products. In order to operate the mating parts near the upper bounds of their theoretical design envelope, manufacturing processes are required that are capable of improving the fatigue life and load bearing capacity of precision parts, while producing the required geometric accuracy. Results of the recent experimental studies indicate that the super finishing process is able to achieve these goals. This paper will review the results of our continuing evaluation of the super finish process as applied to aerospace gearing. Two separate evaluations were performed on gears to examine the effects of super finishing on resistance to both pitting and contact fatigue. For the reported experiments, both conventional and super finished test gears were simultaneously manufactured using the same process and the same heat lot of materials. This paper will also provide a brief description of the manufacturing technology used to achieve the results and will compare the results with other published data. In addition, this paper presents a couple of off-the-shelf manufacturing technologies that have been successfully used to super finish test specimens and will provide a glimpse of other emerging super finishing technologies. This is a US Army Manufacturing Technology project. The project was sponsored by the Aviation and Missiles Command (AMCOM) and was being managed and conducted by IIT Research Institute.

Niskanen, Paul↗

Thermal Structures Technology Development for Reusable Launch Vehicle Cryogenic Propellant Tanks

Analytical and experimental studies conducted at the NASA, Langley Research Center (LaRC) for investigating integrated cryogenic propellant tank systems for a reusable launch vehicle (RLV) are described. The cryogenic tanks are investigated as an integrated tank system. An integrated tank system includes the tank wall, cryogenic insulation, thermal protection system (TPS) attachment sub-structure, and TPS. Analysis codes are used to size the thicknesses of cryogenic insulation and TPS insulation for thermal loads, and to predict tank buckling strengths at various ring frame spacings. The unique test facilities developed for the testing of cryogenic tank components are described. Testing at cryogenic and high-temperatures verifies the integrity of materials, design concepts, manufacturing processes, and thermal/structural analyses. Test specimens ranging from the element level to the subcomponent level are subjected to projected vehicle operational mechanical loads and temperatures. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of light-weight reusable cryogenic propellant tanks.

Johnson, Theodore F.↗

Lessons Learned from Recent Failure and Incident Investigations of Composite Structures

During the past few decades, NASA Langley Research Center (LaRC) has supported several large-scale failure and incident investigations and numerous requests for engineering consultations. Although various extenuating circumstances contributed to each of these incidents, in all cases, the failure resulted from accumulation and/or propagation of damage that reduced the load carrying capability of the structure to a level below that which was needed to sustain structural loads. A brief overview of various failure and incident investigations supported by LaRC, including some of the computational and experimental methodologies that have been applied, is presented. An important outcome of many of these failure and incident investigations is the development of an improved understanding of not only the state-of-the-art in experimental and analytical methods but also the state-of-the-art in the design and manufacturing processes that may contribute to such failures. In order to provide insight into such large-scale investigations, a series of lessons learned were captured. Awareness of these lessons learned is highly beneficial to engineers involved in similar investigations. Therefore, it is prudent that the lessons learned are disseminated such that they can be built upon in other investigations and in ensuing research and development activities.

Ransom, J. B.↗

Design and Manufacturing of Tow-Steered Composite Shells Using Fiber Placement

Advanced composite shells that may offer the potential to improve the structural performance of future aircraft fuselage structures were developed under this joint NASA-industry collaborative effort. Two cylindrical shells with tailored, tow-steered layups and continuously varying fiber angle orientations were designed and built at the National Center for Advanced Manufacturing - Louisiana Partnership. The shells were fabricated from unidirectional IM7/8552 graphite-epoxy pre-preg slit tape material fiber-placed on a constant-diameter mandrel. Each shell had the same nominal 8-ply [plus or minus 45/plus or minus Theta]s layup, where the nominal fiber angle in the tow-steered plies varied continuously from 10 degrees along the crown to 45 degrees on each side, then back to 10 degrees on the keel. One shell was fabricated with all 24 tows placed during each pass of the fiber placement machine, resulting in many tow overlaps on the shell surface. The fiber placement machine's individual tow cut/restart capability was also used to manufacture a second shell with tow drops and a more uniform laminate thickness. This paper presents an overview of the detailed design and manufacturing processes for these shells, and discusses issues encountered during their fabrication and post-cure evaluation. Future plans for structural testing and analyses of the shells are also discussed.

Wu, K. Chauncey↗

Fully Integral, Flexible Composite Driveshaft

An all-composite driveshaft incorporating integral flexible diaphragms was developed for prime contractor testing. This new approach makes obsolete the split lines required to attach metallic flex elements and either metallic or composite spacing tubes in current solutions. Subcritical driveshaft weights can be achieved that are half that of incumbent technology for typical rotary wing shaft lengths. Spacing tubes compose an integral part of the initial tooling but remain part of the finished shaft and control natural frequencies and torsional stability. A concurrently engineered manufacturing process and design for performance competes with incumbent solutions at significantly lower weight and with the probability of improved damage tolerance and fatigue life.

Lawrie, Duncan↗