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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Evolutionary Design of Controlled Structures

Basic physical concepts of structural delay and transmissibility are provided for simple rod and beam structures. Investigations show the sensitivity of these concepts to differing controlled-structures variables, and to rational system modeling effects. An evolutionary controls/structures design method is developed. The basis of the method is an accurate model formulation for dynamic compensator optimization and Genetic Algorithm based updating of sensor/actuator placement and structural attributes. One and three dimensional examples from the literature are used to validate the method. Frequency domain interpretation of these controlled structure systems provide physical insight as to how the objective is optimized and consequently what is important in the objective. Several disturbance rejection type controls-structures systems are optimized for a stellar interferometer spacecraft application. The interferometric designs include closed loop tracking optics. Designs are generated for differing structural aspect ratios, differing disturbance attributes, and differing sensor selections. Physical limitations in achieving performance are given in terms of average system transfer function gains and system phase loss. A spacecraft-like optical interferometry system is investigated experimentally over several different optimized controlled structures configurations. Configurations represent common and not-so-common approaches to mitigating pathlength errors induced by disturbances of two different spectra. Results show that an optimized controlled structure for low frequency broadband disturbances achieves modest performance gains over a mass equivalent regular structure, while an optimized structure for high frequency narrow band disturbances is four times better in terms of root-mean-square pathlength. These results are predictable given the nature of the physical system and the optimization design variables. Fundamental limits on controlled performance are discussed based on the measured and fit average system transfer function gains and system phase loss.

Masters, Brett P.↗
DOE OSTI2022

Rapid approach for structural design of the tower and monopile for a series of 25 MW offshore turbines

The goal of further reducing the Levelized Cost of Energy (LCOE) has driven the investigation of large-scale wind turbines. This work presents a simple, rapid and detailed approach for the structural design of the tower and monopile without a controller, but with frequency and high fidelity structural verification. The approach uses an optimization to reduce the mass of the structures while meeting strength, buckling and geometric constraints by using analytical equations. A verification of frequency constraints is performed with BModes, and ANSYS Mechanical APDL is used for high fidelity verification of stress and buckling. The approach is applied to study the design space of three 25 MW offshore wind turbines with different rotor diameters and cone angles, and to evaluate the nacelle center of mass fore-aft location effect. Results obtained show that the tower and monopile are more susceptible to changes in the rotor thrust than the overturning moment even for designs with high pre-cone angle and large distance of the nacelle center of mass from the tower axis. But it is possible to obtain structurally feasible tower and monopile designs for the three 25 MW turbines studied while not exceeding diameter and wall thickness limits. However, mass penalties can be decreased by 0.8-14%, to further reduce the cost of energy, by increasing the diameter limit which may require manufacturing technology development. The approach applied and studies serve to understand the design space of the tower and monopile for a 25 MW turbine, and provide baseline designs that can be used in the development of a controller and evaluation of a full suite of design load cases.

17 WIND ENERGY↗
NASA NTRS2005

Structural Benchmark Tests of Composite Combustion Chamber Support Completed

A series of mechanical load tests was completed on several novel design concepts for extremely lightweight combustion chamber support structures at the NASA Glenn Research Center (http://www.nasa.gov/glenn/). The tests included compliance evaluation, preliminary proof loadings, high-strain cyclic testing, and finally residual strength testing of each design (see the photograph on the left). Loads were applied with single rollers (see the photograph on the right) or pressure plates (not shown) located midspan on each side to minimize the influence of contact stresses on corner deformation measurements. Where rollers alone were used, a more severe structural loading was produced than the corresponding equal-force pressure loading: the maximum transverse shear force existed over the entire length of each side, and the corner bending moments were greater than for a distributed (pressure) loading. Failure modes initiating at the corner only provided a qualitative indication of the performance limitations since the stress state was not identical to internal pressure. Configurations were tested at both room and elevated temperatures. Experimental results were used to evaluate analytical prediction tools and finite-element methodologies for future work, and they were essential to provide insight into the deformation at the corners. The tests also were used to assess fabrication and bonding details for the complicated structures. They will be used to further optimize the design of the support structures for weight performance and the efficacy of corner reinforcement.

Krause, David L.↗
DOE OSTI2017

GeneratorSE: A Sizing Tool for Variable-Speed Wind Turbine Generators

This report documents a set of analytical models employed by the optimization algorithms within the GeneratorSE framework. The initial values and boundary conditions employed for the generation of the various designs and initial estimates for basic design dimensions, masses, and efficiency for the four different models of generators are presented and compared with empirical data collected from previous studies and some existing commercial turbines. These models include designs applicable for variable-speed, high-torque application featuring direct-drive synchronous generators and low-torque application featuring induction generators. In all of the four models presented, the main focus of optimization is electromagnetic design with the exception of permanent-magnet and wire-wound synchronous generators, wherein the structural design is also optimized. Thermal design is accommodated in GeneratorSE as a secondary attribute by limiting the winding current densities to acceptable limits. A preliminary validation of electromagnetic design was carried out by comparing the optimized magnetic loading against those predicted by numerical simulation in FEMM4.2, a finite-element software for analyzing electromagnetic and thermal physics problems for electrical machines. For direct-drive synchronous generators, the analytical models for the structural design are validated by static structural analysis in ANSYS.

17 WIND ENERGY↗
NASA NTRS2023

Reduction in Computational Cost of Progressive Failure Analysis of Composite Structures

Designing aircraft structures requires efficient modeling approaches to iterate on multiple structural configurations to achieve an optimal design. Typically, damage tolerance is not considered at the design stage because of the high computational cost in its implementation within a finite element modeling approach. Therefore, analytical or empirical approaches are often used to size critical damage-tolerant structures once an optimal design is determined. In this study, the Progressive Release eXplicit Virtual Crack-Closure Technique (PRX-VCCT) is assessed for its capability to cost-effectively evaluate skin stringer separation of a blade-stiffened panel that is subjected to seven point bend loads. An initial verification study was performed to evaluate PRX VCCT to accurately simulate skin-stringer separation with respect to existing cohesive element approaches. Furthermore, the influence of element size, ranging from 0.10 in. to 0.40 in., on the total computational time using the PRX-VCCT is investigated. The results indicate that the PRX-VCCT can be used to accurately simulate skin stringer separation using large element lengths (0.40 in.). Additionally, a significant reduction in the computational time to simulate skin stringer separation is observed using the PRX-VCCT. Large-scale progressive damage analysis using PRX-VCCT can be implemented early in the design cycle of composite structures without requiring a global-to-local modeling approach.

Composites↗
DOE OSTI2019

Optimization of Energy Absorbing Materials for Radioactive Packaging

Most applications of honeycomb materials are for lightweight structural members. This area of honeycomb material behavior has been extensively researched. In packaging design, honeycomb materials are used for impact energy absorption. Data concerning the deformation of stainless steel honeycomb structures is not widely available. It is being proposed to use honeycomb stainless steel as an impact energy absorber in a new radioactive material shipping package. Honeycomb materials can be useful for energy absorption applications because the geometry causes the structure to have a constant compressive force during buckling. This Finite Element Analysis is used to predict the compressive buckling strength of various honeycomb structures in order to design an energy absorber for a specific package weight and geometry. The model simulates a drop test where a 50 pound plate lands flat on a honeycomb stainless steel structure from a height of 30 feet. Some actual drop tests have already been performed on real specimens. Most of the resulting deformations of these tests include the bottom of the honeycomb structure buckling while the rest of the structure was either slightly deformed or straight. The deformation of the simulated honeycomb specimen matched the deformation from the actual drop tests. This is one verification that the model is working properly. It is evident that after about 2.5% strain the strength is a relatively linear value, and eventually flattens out to about 875 psi. The crush strength measured from the actual drop tests for the same density honeycomb was just over 800 psi. This is further verification that the model is working correctly. The results gathered from the FEA model successfully mirror the results from a real drop test. The deformation looks realistic, and the compressive strength found is consistent with the empirically measured value. Future work for this model includes modeling different density honeycomb structures which have not been tested before. This will allow for optimization of honeycomb stainless steel use for impact absorption in radioactive material shipping packages.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Experimental Validation of an Additively Manufactured Stiffness-Optimized Short-Fiber Reinforced Composite Clevis Joint

This effort describes experiments for the validation of the response of an additively manufactured stiffness-optimized short-fiber reinforced composite. A Direct Ink Write (DIW) method is used to additively manufacture a clevis joint plate which was designed such that its compliance would be minimized (i.e., stiffness maximized) for far-field axial loading. A unique aspect of the optimization scheme is that it accounts for manufacturing constraints, such as tool turn radius and tool path spacing. Along with the optimized clevis joint plate, additively manufactured 0°–90° and ± 45° composite plates of the same number of layers, as well as a control 0°–90° sample of resin only, were also studied. In addition to far-field load-displacement, near-field strain was monitored using digital image correlation (DIC). The results showed that the optimized plate did indeed exhibit the largest stiffness, based on far-field measurements. DIC-measured strains showed that locally the axial strain component, which is the largest, was also minimized for the optimized specimen, although the other strain components followed different trends. Furthermore, in the experiments it was seen that the optimized design exhibited a nonlinear/hysteretic behavior which is believed to be a consequence of its internal gap/cell structure. This internal structure, which results by optimized placement of material, although explicitly not accounted for in the optimization, may affect global response. Lastly, although not a part of the optimization study itself, the failure load for the optimized joint plate was also seen to be the largest of all the cases studied.

42 ENGINEERING↗
NASA NTRS1984

Loads and aeroelasticity division research and technology accomplishments for FY 1983 and plans for FY 1984

Research was done in the following areas: development and validation of solution algorithms, modeling techniques, integrated finite elements for flow-thermal-structural analysis and design, optimization of aircraft and spacecraft for the best performance, reduction of loads and increase in the dynamic structural stability of flexible airframes by the use of active control, methods for predicting steady and unsteady aerodynamic loads and aeroelastic characteristics of flight vehicles with emphasis on the transonic range, and methods for predicting and reducing helicoper vibrations.

Gardner, J. E.↗
NASA NTRS1992

Multidisciplinary design integration system for a supersonic transport aircraft

An aircraft preliminary design system which provides the multidisciplinary communications and couplings between several engineering disciplines is described. A primary benefit of this system is to demonstrate advanced technology multidisciplinary design integration methodologies. The current version includes the disciplines of aerodynamics and structures. Contributing engineering disciplines are coupled using the Global Sensitivity Equation approach to influence the global design optimization problem. A high speed civil transport configuration is used for configuration trade studies. Forty four independent design variables are used to control the cross-sectional areas of wing rib and spar caps and the thicknesses of wingskincover panels. A total of 300 stress, strain, buckling and displacement behavioral constraints and minimum gages on the design variables were used to optimize the idealized wing structure. The goal of the designs to resize the wing cover panels and internal structure for minimum mass.

Dovi, A. R.↗
NASA NTRSDate not supplied

Multidisciplinary Design Optimization and Analysis of an Open Rotor Stage: Part 1

Successful design of open rotor propulsors requires effective analysis across multiple disciplines, including aerodynamics, acoustics, and structures. A viable design must not only be efficient but must also produce an acceptable level of noise and meet all static and dynamic structural requirements. For design and optimization, this is especially challenging because running high fidelity analyses is resource-intensive, and optimizing a design may require many thousands of cases to be analyzed. For this reason, the NASA team has applied design methodology that utilizes low-cost aerodynamic methods, machine learning models, and high-fidelity analyses when necessary. This includes standard two-dimensional methods such as throughflow analysis and quasi-3D blade-to-blade CFD, as well as some newly developed methods. Optimization using 3D CFD is necessary to maximize performance, and this is considered as well. All optimizations are carried out subject to structural constraints evaluated using finite element analysis. Doing this accurately requires a robust trunnion design, capable of pitching the blade between cruise and takeoff conditions while maintaining acceptable factor of safety. Hot to cold analysis must also be applied in order to correctly determine the as-manufactured shape. For acoustics, the unsteady pressures on the blade surfaces must be predicted, and this can be done either through full-annulus unsteady CFD or through a nonlinear harmonic method (NLH). NLH can run much faster, allowing some acoustic considerations to be made earlier in the design process. The design process is ongoing, and this presentation will review the current status and planned next steps. This part of the talk will focus on aerodynamic performance and be followed by a talk on structures and acoustics.

Design↗
DOE OSTI2017

LDRD Report: Topological Design Optimization of Convolutes in Next Generation Pulsed Power Devices.

This LDRD project was developed around the ambitious goal of applying PDE-constrained opti- mization approaches to design Z-machine components whose performance is governed by elec- tromagnetic and plasma models. This report documents the results of this LDRD project. Our differentiating approach was to use topology optimization methods developed for structural design and extend them for application to electromagnetic systems pertinent to the Z-machine. To achieve this objective a suite of optimization algorithms were implemented in the ROL library part of the Trilinos framework. These methods were applied to standalone demonstration problems and the Drekar multi-physics research application. Out of this exploration a new augmented Lagrangian approach to structural design problems was developed. We demonstrate that this approach has favorable mesh-independent performance. Both the final design and the algorithmic performance were independent of the size of the mesh. In addition, topology optimization formulations for the design of conducting networks were developed and demonstrated. Of note, this formulation was used to develop a design for the inner magnetically insulated transmission line on the Z-machine. The resulting electromagnetic device is compared with theoretically postulated designs.

42 ENGINEERING↗
NASA NTRS1977

Optimization of MLS receivers for multipath environments

Optimal design studies of MLS angle-receivers and a theoretical design-study of MLS DME-receivers are reported. The angle-receiver results include an integration of the scan data processor and tracking filter components of the optimal receiver into a unified structure. An extensive simulation study comparing the performance of the optimal and threshold receivers in a wide variety of representative dynamical interference environments was made. The optimal receiver was generally superior. A simulation of the performance of the threshold and delay-and-compare receivers in various signal environments was performed. An analysis of combined errors due to lateral reflections from vertical structures with small differential path delays, specular ground reflections with neglible differential path delays, and thermal noise in the receivers is provided.

Mcalpine, G. A.↗
NASA NTRS1976

Computer-aided design of antenna structures and components

This paper discusses computer-aided design procedures for antenna reflector structures and related components. The primary design aid is a computer program that establishes cross sectional sizes of the structural members by an optimality criterion. Alternative types of deflection-dependent objectives can be selected for designs subject to constraints on structure weight. The computer program has a special-purpose formulation to design structures of the type frequently used for antenna construction. These structures, in common with many in other areas of application, are represented by analytical models that employ only the three translational degrees of freedom at each node. The special-purpose construction of the program, however, permits coding and data management simplifications that provide advantages in problem size and execution speed. Size and speed are essentially governed by the requirements of structural analysis and are relatively unaffected by the added requirements of design. Computation times to execute several design/analysis cycles are comparable to the times required by general-purpose programs for a single analysis cycle. Examples in the paper illustrate effective design improvement for structures with several thousand degrees of freedom and within reasonable computing times.

Levy, R.↗
NASA NTRS1980

PROCRU: A model for analyzing crew procedures in approach to landing

A model for analyzing crew procedures in approach to landing is developed. The model employs the information processing structure used in the optimal control model and in recent models for monitoring and failure detection. Mechanisms are added to this basic structure to model crew decision making in this multi task environment. Decisions are based on probability assessments and potential mission impact (or gain). Sub models for procedural activities are included. The model distinguishes among external visual, instrument visual, and auditory sources of information. The external visual scene perception models incorporate limitations in obtaining information. The auditory information channel contains a buffer to allow for storage in memory until that information can be processed.

Baron, S.↗
NASA NTRS1992

A perspective on technical needs in computational structures technology

The wide spectrum of needs and applications are demonstrated of computational structural mechanics. The spectrum ranges from micro structural mechanics to the optimization of the performance of aerovehicles. Critical high leveraged technologies will require engineering process modernization and automation, affordable structures and materials, and advanced computational technology. Recent advances at Rockwell International in computational structural mechanics addressed these issues and improve the ability to achieve advanced aircraft objectives.

Abdi, Frank F.↗
DOE OSTI2022

LigninGraphs: lignin structure determination with multiscale graph modeling

Lignin is an aromatic biopolymer found in ubiquitous sources of woody biomass. Designing and optimizing lignin valorization processes requires a fundamental understanding of lignin structures. Experimental characterization techniques, such as 2D-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra, could elucidate the global properties of the polymer molecules. Computer models could extend the resolution of experiments by representing structures at the molecular and atomistic scales. We introduce a graph-based multiscale modeling framework for lignin structure generation and visualization. The framework employs accelerated rejection-free polymerization and hierarchical Metropolis Monte Carlo optimization algorithms. We obtain structure libraries for various lignin feedstocks based on literature and new experimental NMR data for poplar wood, pinewood, and herbaceous lignin. The framework could guide researchers towards feasible lignin structures, efficient space exploration, and future kinetics modeling. Its software implementation in Python, LigninGraphs, is open-source and available on GitHub.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

An improved algorithm for optimum structural design with multiple frequency constraints

An optimality criterion (OC) method for minimum-weight design of structures having multiple constraints on natural frequencies is presented. In this work a new resizing strategy is developed based on relaxation techniques. A computationally adaptive control parameter is used in conjunction with existing OC recursive formulae to promote convergence of optimum structural designs. Some considerations regarding the coupling of the modified Aitken accelerator with the OC method are discussed. Improved and rapidly converged minimum-weight designs are obtained when using an under-relaxed recursive scheme combined with the modified Aitken accelerator.

Mcgee, Oliver G.↗
NASA NTRS1993

Integrated design and experimental validation of the CSI evolutionary structure

An experimental validation of the optimization-based integrated design methodology performed under the Controls-Structures Interaction (CSI) program for a class of flexible spacecraft is reviewed. The studies have been performed using an integrated design software tool which is under development at the NASA-Langley Research Center. It is analytically and experimentally demonstrated that integrated controls-structures design can yield designs which are substantially superior to those obtained through the traditional sequential approach.

Maghami, P. G.↗