An integrated team of NASA personnel, Government contractors, industry partners, and university staff have developed an innovative new technology for commercial fan cases that will substantially influence the safety and efficiency of future turbine engines. This effective team, under the direction of the NASA Glenn Research Center and with the support of the Federal Aviation Administration, has matured a new class of carbon/polymer composites and demonstrated a 30- to 50-percent improvement in...

Topics: NASA Technical Reports Server (NTRS), TECHNOLOGY ASSESSMENT, ENGINE PARTS, FANS, MANUFACTURING,...

A key challenge in designing the new High Speed Civil Transport (HSCT) aircraft is determining a good match between the airframe and engine. Multidisciplinary design optimization can be used to solve the problem by adjusting parameters of both the engine and the airframe. Earlier, an example problem was presented of an HSCT aircraft with four mixed-flow turbofan engines and a baseline mission to carry 305 passengers 5000 nautical miles at a cruise speed of Mach 2.4. The problem was solved by...

Topics: NASA Technical Reports Server (NTRS), AIRCRAFT DESIGN, MULTIDISCIPLINARY DESIGN OPTIMIZATION,...

For a truss a fully stressed state is reached and when all its members are utilized to their full strength capacity. Historically, engineers considered such a design optimum. But recently this optimality has been questioned, especially since the weight of the structure is not explicitly used in fully stressed design calculations. This paper examines optimality of the full stressed design (FSD) with analytical and graphical illustrations. Solutions for a set of examples obtained by using the FSD...

Topics: NASA Technical Reports Server (NTRS), TRUSSES, DESIGN, LOAD DISTRIBUTION (FORCES), LOADS (FORCES),...

A preliminary methodology was obtained for the design optimization of a subsonic aircraft by coupling NASA Langley Research Center s Flight Optimization System (FLOPS) with NASA Glenn Research Center s design optimization testbed (COMETBOARDS with regression and neural network analysis approximators). The aircraft modeled can carry 200 passengers at a cruise speed of Mach 0.85 over a range of 2500 n mi and can operate on standard 6000-ft takeoff and landing runways. The design simulation was...

Topics: NASA Technical Reports Server (NTRS), DESIGN ANALYSIS, DESIGN OPTIMIZATION, FLIGHT OPTIMIZATION,...

Design optimization of large systems can be attempted through a sub-problem strategy. In this strategy, the original problem is divided into a number of smaller problems that are clustered together to obtain a sequence of sub-problems. Solution to the large problem is attempted iteratively through repeated solutions to the modest sub-problems. This strategy is applicable to structures and to multidisciplinary systems. For structures, clustering the substructures generates the sequence of...

Topics: NASA Technical Reports Server (NTRS), NEURAL NETS, DESIGN OPTIMIZATION, SUBSTRUCTURES, SENSITIVITY...

The neural network and regression methods of NASA Glenn Research Center s COMETBOARDS design optimization testbed were used to generate approximate analysis and design models for a subsonic aircraft operating at Mach 0.85 cruise speed. The analytical model is defined by nine design variables: wing aspect ratio, engine thrust, wing area, sweep angle, chord-thickness ratio, turbine temperature, pressure ratio, bypass ratio, fan pressure; and eight response parameters: weight, landing velocity,...

Topics: NASA Technical Reports Server (NTRS), DESIGN OPTIMIZATION, DESIGN ANALYSIS, AIRCRAFT MODELS, NEURAL...

A preliminary aircraft engine design methodology is being developed that utilizes a cascade optimization strategy together with neural network and regression approximation methods. The cascade strategy employs different optimization algorithms in a specified sequence. The neural network and regression methods are used to approximate solutions obtained from the NASA Engine Performance Program (NEPP), which implements engine thermodynamic cycle and performance analysis models. The new methodology...

Topics: NASA Technical Reports Server (NTRS), NEURAL NETS, REGRESSION ANALYSIS, ENGINE DESIGN, DESIGN...

Design sensitivity is central to most optimization methods. The analytical sensitivity expression for an indeterminate structural design optimization problem can be factored into a simple determinate term and a complicated indeterminate component. Sensitivity can be approximated by retaining only the determinate term and setting the indeterminate factor to zero. The optimum solution is reached with the approximate sensitivity. The central processing unit (CPU) time to solution is substantially...

Topics: NASA Technical Reports Server (NTRS), DESIGN OPTIMIZATION, SENSITIVITY, STRUCTURAL DESIGN,...

Strength of materials problems have been classified into determinate and indeterminate problems. Determinate analysis primarily based on the equilibrium concept is well understood. Solutions of indeterminate problems required additional compatibility conditions, and its comprehension was not exclusive. A solution to indeterminate problem is generated by manipulating the equilibrium concept, either by rewriting in the displacement variables or through the cutting and closing gap technique of the...

Topics: NASA Technical Reports Server (NTRS), STRUCTURAL ANALYSIS, COMPATIBILITY, DISPLACEMENT, EQUILIBRIUM...

Dynamic animation of stresses and displacements, which complement each other, can be a useful tool in the analysis and design of structural components. At the present time only displacement-mode animation is available through the popular stiffness formulation. This paper attempts to complete this valuable visualization tool by augmenting the existing art with stress mode animation. The reformulated method of forces, which in the literature is known as the integrated force method (IFM), became...

Topics: NASA Technical Reports Server (NTRS), STRESS ANALYSIS, STRUCTURAL DESIGN, DESIGN ANALYSIS,...

The boundary element method is utilized to analyze the effects of fiber/matrix interfaces on the micromechanical behavior of laminated composites as well as the elastic behavior of woven composites. Effective composite properties are computed for laminated SiC/RBSN and SiC/Ti-15-3 composites, as well as a woven SiC/SiC composite. The properties calculated using the computerized tool BEST-CMS match the experimental results well.

Topics: NASA Technical Reports Server (NTRS), BOUNDARY ELEMENT METHOD, LAMINATES, SILICON CARBIDES, WOVEN...

At the NASA Glenn Research Center, the NASA engine performance program (NEPP, ref. 1) and the design optimization testbed COMETBOARDS (ref. 2) with regression and neural network analysis-approximators have been coupled to obtain a preliminary engine design methodology. The solution to a high-bypass-ratio subsonic waverotor-topped turbofan engine, which is shown in the preceding figure, was obtained by the simulation depicted in the following figure. This engine is made of 16 components mounted...

Topics: NASA Technical Reports Server (NTRS), ENGINE DESIGN, REGRESSION ANALYSIS, NEURAL NETS, DESIGN...

A set of conditions had not been formulated on the boundary of an elastic continuum since the time of Saint-Venant. This limitation prevented the formulation of a direct stress calculation method in elasticity for a continuum with a displacement boundary condition. The missed condition, referred to as the boundary compatibility condition, is now formulated in polar coordinates. The augmentation of the new condition completes the Beltrami-Michell formulation in polar coordinates. The completed...

Topics: NASA Technical Reports Server (NTRS), MICHELL THEOREM, POLAR COORDINATES, PARAMETERIZATION,...

The theory of elasticity evolved over centuries through the contributions of eminent scientists like Cauchy, Navier, Hooke Saint Venant, and others. It was deemed complete when Saint Venant provided the strain formulation in 1860. However, unlike Cauchy, who addressed equilibrium in the field and on the boundary, the strain formulation was confined only to the field. Saint Venant overlooked the compatibility on the boundary. Because of this deficiency, a direct stress formulation could not be...

Topics: NASA Technical Reports Server (NTRS), MICHELL THEOREM, MATHEMATICAL MODELS, BOUNDARY CONDITIONS,...

The boundary element method is utilized in this study to conduct thermal analysis of functionally graded composites, materials in which the internal microstructure or properties are explicitly tailored in order to obtain an optimal response, on the micromechanical (constituent) scale. A unique feature of the boundary element formulations used here is the use of circular shape functions to convert the two-dimensional integrations of the composite fibers to one dimensional integrations. Using the...

Topics: NASA Technical Reports Server (NTRS), BOUNDARY ELEMENT METHOD, FIBER COMPOSITES, MICROMECHANICS,...

Design optimization of large structural systems can be attempted through a substructure strategy when convergence difficulties are encountered. When this strategy is used, the large structure is divided into several smaller substructures and a subproblem is defined for each substructure. The solution of the large optimization problem can be obtained iteratively through repeated solutions of the modest subproblems. Substructure strategies, in sequential as well as in parallel computational modes...

Topics: NASA Technical Reports Server (NTRS), MULTIPROCESSING (COMPUTERS), STRUCTURAL ANALYSIS,...

The use of the boundary element method for analyzing composite micromechanical behavior is demonstrated. Stress-strain, heat conduction, and thermal expansion analyses are conducted using the boundary element computer code BEST-CMS, and the results obtained are compared to experimental observations, analytical calculations, and finite element analyses. For each of the analysis types, the boundary element results agree reasonably well with the results from the other methodologies, with...

Topics: NASA Technical Reports Server (NTRS), BOUNDARY ELEMENT METHOD, COMPOSITE MATERIALS, MATHEMATICAL...

At the NASA Glenn Research Center, NASA Langley Research Center's Flight Optimization System (FLOPS) and the design optimization testbed COMETBOARDS with regression and neural-network-analysis approximators have been coupled to obtain a preliminary aircraft design methodology. For a subsonic aircraft, the optimal design, that is the airframe-engine combination, is obtained by the simulation. The aircraft is powered by two high-bypass-ratio engines with a nominal thrust of about 35,000 lbf. It...

Topics: NASA Technical Reports Server (NTRS), APPROXIMATION, NEURAL NETS, SUBSONIC AIRCRAFT, REGRESSION...

Two methods of solving indeterminate structural-mechanics problems have been developed as products of research on the theory of strain compatibility. In these methods, stresses are considered to be the primary unknowns (in contrast to strains and displacements being considered as the primary unknowns in some prior methods). One of these methods, denoted the integrated force method (IFM), makes it possible to compute stresses, strains, and displacements with high fidelity by use of modest...

Topics: NASA Technical Reports Server (NTRS), STRUCTURAL ANALYSIS, COMPUTATION, ELASTIC PROPERTIES,...

In fiscal year 2001, the neural network and regression capabilities of NASA Glenn Research Center's COMETBOARDS design optimization testbed were extended to generate approximate models for the PAX-300 aircraft engine. The analytical model of the engine is defined through nine variables: the fan efficiency factor, the low pressure of the compressor, the high pressure of the compressor, the high pressure of the turbine, the low pressure of the turbine, the operating pressure, and three critical...

Topics: NASA Technical Reports Server (NTRS), NEURAL NETS, DESIGN OPTIMIZATION, EXPERIMENT DESIGN,...

The theory of elasticity has camouflaged a deficiency in the compatibility formulation since 1860. In structures the ad hoc compatibility conditions through virtual "cuts" and closing "gaps" are not parallel to the strain formulation in elasticity. This deficiency in the compatibility conditions has prevented the development of a direct stress determination method in structures and in elasticity. We have addressed this deficiency and attempted to unify the theory of...

Topics: NASA Technical Reports Server (NTRS), COMPATIBILITY, ELASTIC PROPERTIES, FINITE ELEMENT METHOD,...

Non-linear programming algorithms play an important role in structural design optimization. Fortunately, several algorithms with computer codes are available. At NASA Lewis Research Centre, a project was initiated to assess the performance of eight different optimizers through the development of a computer code CometBoards. This paper summarizes the conclusions of that research. CometBoards was employed to solve sets of small, medium and large structural problems, using the eight different...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, QUADRATIC PROGRAMMING, CRAY COMPUTERS,...

The Structural Tailoring of Advanced Turboprops (STAT) computer program was developed to perform numerical optimization on highly swept propfan blades. The optimization procedure seeks to minimize an objective function defined as either: (1) direct operating cost of full scale blade or, (2) aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. The STAT analysis system includes an...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, FAN BLADES, OPTIMIZATION, STRESS ANALYSIS,...

The design optimization of air-breathing propulsion engine concepts has been accomplished by soft-coupling the NASA Engine Performance Program (NEPP) analyzer with the NASA Lewis multidisciplinary optimization tool COMETBOARDS. Engine problems, with their associated design variables and constraints, were cast as nonlinear optimization problems with thrust as the merit function. Because of the large number of mission points in the flight envelope, the diversity of constraint types, and the...

Topics: NASA Technical Reports Server (NTRS), AIR BREATHING ENGINES, OPTIMIZATION, ENGINE DESIGN, ENGINE...

In elasticity, the method of forces, wherein stress parameters are considered as the primary unknowns, is known as the Beltrami-Michell formulation (BMF). The existing BMF can only solve stress boundary value problems; it cannot handle the more prevalent displacement of mixed boundary value problems of elasticity. Therefore, this formulation, which has restricted application, could not become a true alternative to the Navier's displacement method, which can solve all three types of boundary...

Topics: NASA Technical Reports Server (NTRS), BOUNDARY VALUE PROBLEMS, CIRCULAR PLATES, CYLINDRICAL SHELLS,...

Metal matrix composites (MMC) are the subject of intensive study and are receiving serious consideration for critical structural applications in advanced aerospace systems. MMC structural analysis and design methodologies are studied. Predicting the mechanical and thermal behavior and the structural response of components fabricated from MMC requires the use of a variety of mathematical models. These models relate stresses to applied forces, stress intensities at the tips of cracks to nominal...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, METAL MATRIX COMPOSITES, STRUCTURAL...

Optimization research at NASA Glenn Research Center has addressed the design of structures, aircraft and airbreathing propulsion engines. During solution of the multidisciplinary problems several issues were encountered. This paper lists four issues and discusses the strategies adapted for their resolution: (1) The optimization process can lead to an inefficient local solution. This deficiency was encountered during design of an engine component. The limitation was overcome through an...

Topics: NASA Technical Reports Server (NTRS), RESEARCH AND DEVELOPMENT, AIRCRAFT DESIGN, ENGINE DESIGN,...

Recently, a relatively new industrial fiber known by the trade name Zylon has been under commercial development by Toyobo Co., Ltd., Japan. In ballistic impact tests conducted at the NASA Glenn Research Center, it was found that dry fabric braided of Zylon had greater ballistic impact capacity than comparable (braid style and weight) fabric braided of Kevlar. To study the potential use of Zylon fabric in jet engine containment systems, the fabric was tested in Glenn's Structures and Acoustics...

Topics: NASA Technical Reports Server (NTRS), FABRICS, FABRICATION, KEVLAR (TRADEMARK), TERMINAL...

This paper investigates the feasibility of a proposed technique for detecting delamination using piezoelectric layers or patches embedded or bonded to a composite structure. Variations in the voltage generated in the piezoelectric layers indicates the presence and location of delamination, when the structure is excited either externally or via actuators. The theoretical foundations of a method for predicting the dynamic response of delaminated composite beams with piezoelectric layers are...

Topics: NASA Technical Reports Server (NTRS), BEAMS (SUPPORTS), COMPOSITE STRUCTURES, DELAMINATING,...

An overview is presented of current research activities which, in a broad context, are focused on the development and verification of integrated structural analysis and optimal design capabilities for advanced aerospace propulsion and power systems. The overview encompasses a variety of subject areas including: (1) composite materials; (2) advanced structural analysis; (3) constitutive modeling; (4) computational simulation; (5) probabilistic analysis; and (6) multidisciplinary optimization....

Topics: NASA Technical Reports Server (NTRS), PROPULSION SYSTEM CONFIGURATIONS, SPACECRAFT DESIGN,...

The preliminary design of three major structural components within NASA's Ares V heavy lift vehicle using a novel fiber reinforced foam composite sandwich panel concept is presented. The Ares V payload shroud, interstage, and core intertank are designed for minimum mass using this panel concept, which consists of integral composite webs separated by structural foam between two composite facesheets. The HyperSizer structural sizing software, in conjunction with NASTRAN finite element analyses,...

Topics: NASA Technical Reports Server (NTRS), ARES 5 CARGO LAUNCH VEHICLE, FIBER COMPOSITES, FOAMS,...

A force method formulation, the completed Beltrami-Michell formulation (CBMF), has been developed for analyzing boundary value problems in elastic continua. The CBMF is obtained by augmenting the classical Beltrami-Michell formulation with novel boundary compatibility conditions. It can analyze general elastic continua with stress, displacement, or mixed boundary conditions. The CBMF alleviates the limitations of the classical formulation, which can solve stress boundary value problems only. In...

Topics: NASA Technical Reports Server (NTRS), BOUNDARY VALUE PROBLEMS, ELASTIC BODIES, PLATES (STRUCTURAL...

A select overview is provided of ongoing research focusing on the development and verification of integrated structural analysis and optimal design capabilities for advanced aerospace propulsion and power systems. Subjects discussed include the following: (1) Composites - analytical models (composite mechanics), integrated computational methods, and characterization of composite structural response and durability for resin-, metal-, and ceramic-matrix systems; (2) Advanced inelastic analysis -...

Topics: NASA Technical Reports Server (NTRS), DESIGN ANALYSIS, INTEGRATED ENERGY SYSTEMS, OPTIMIZATION,...

Nonlinear programming algorithms play an important role in structural design optimization. Fortunately, several algorithms with computer codes are available. At NASA Lewis Research Center, a project was initiated to assess performance of different optimizers through the development of a computer code CometBoards. This paper summarizes the conclusions of that research. CometBoards was employed to solve sets of small, medium and large structural problems, using different optimizers on a...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, NONLINEAR PROGRAMMING, STRUCTURAL DESIGN,...

A brief description is provided of the fundamental aspects of a quantification process. Progress since the last structural durability conference in 1989 is summarized. The methodology to date and that to be developed during the life of the program is presented. The uncertain factors are presented. The approach is outlined that is required to achieve component and/or system certification in the shortest possible time for affordable reliability risk. Two new elements appear in a block diagram:...

Topics: NASA Technical Reports Server (NTRS), AEROSPACE VEHICLES, COMPUTER AIDED DESIGN, CYCLIC LOADS,...

Minimizing the weight of structural components of the space station launched into orbit in a space shuttle can save cost, reduce the number of space shuttle missions, and facilitate on-orbit fabrication. Traditional manual design of such components, although feasible, cannot represent a minimum weight condition. At NASA Lewis Research Center, a design capability called CometBoards (Comparative Evaluation Test Bed of Optimization and Analysis Routines for the Design of Structures) has been...

Topics: NASA Technical Reports Server (NTRS), COMPUTER AIDED DESIGN, SPACE STATION FREEDOM, SPACE STATION...

The NASA Engine Performance Program (NEPP) can configure and analyze almost any type of gas turbine engine that can be generated through the interconnection of a set of standard physical components. In addition, the code can optimize engine performance by changing adjustable variables under a set of constraints. However, for engine cycle problems at certain operating points, the NEPP code can encounter difficulties: nonconvergence in the currently implemented Powell's optimization algorithm and...

Topics: NASA Technical Reports Server (NTRS), AIRCRAFT ENGINES, NEURAL NETS, REGRESSION ANALYSIS,...

Analytical procedures are developed for a composite system consisting of shape memory alloy fibers within an elastic matrix subject to uniform temperature fluctuations. Micromechanics for the calculation of the equivalent properties of the composite are presented by extending the multi-cell model to incorporate shape memory alloy fibers. A three phase concentric cylinder model is developed for the analysis of local stresses which includes the fiber, the matrix, and the surrounding homogenized...

Topics: NASA Technical Reports Server (NTRS), FIBER COMPOSITES, MARTENSITIC TRANSFORMATION, METAL FIBERS,...

This conference publication contains the presentations and discussions from the joint UVA/NASA Workshop on Computational Methods for Failure Analysis and Life Prediction held at NASA Langley Research Center 14-15 Oct. 1992. The presentations focused on damage failure and life predictions of polymer-matrix composite structures. They covered some of the research activities at NASA Langley, NASA Lewis, Southwest Research Institute, industry, and universities. Both airframes and propulsion systems...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, CONFERENCES, FAILURE ANALYSIS, LIFE...

The basic theory of solid mechanics was deemed complete circa 1860 when St. Venant provided the strain formulation or the field compatibility condition. The strain formulation was incomplete. The missing portion has been formulated and identified as the boundary compatibility condition (BCC). The BCC, derived through a variational formulation, has been verified through integral theorem and solution of problems. The BCC, unlike the field counterpart, do not trivialize when expressed in...

Topics: NASA Technical Reports Server (NTRS), MATHEMATICAL MODELS, SOLID MECHANICS, MECHANICAL PROPERTIES,...

Design optimization for subsonic and supersonic aircraft and for air-breathing propulsion engine concepts has been accomplished by soft-coupling the Flight Optimization System (FLOPS) and the NASA Engine Performance Program analyzer (NEPP), to the NASA Lewis multidisciplinary optimization tool COMETBOARDS. Aircraft and engine design problems, with their associated constraints and design variables, were cast as nonlinear optimization problems with aircraft weight and engine thrust as the...

Topics: NASA Technical Reports Server (NTRS), AIR BREATHING ENGINES, AIRCRAFT DESIGN, AIRCRAFT ENGINES,...

Nonlinear mathematical-programming-based design optimization can be an elegant method. However, the calculations required to generate the merit function, constraints, and their gradients, which are frequently required, can make the process computational intensive. The computational burden can be greatly reduced by using approximating analyzers derived from an original analyzer utilizing neural networks and linear regression methods. The experience gained from using both of these approximation...

Topics: NASA Technical Reports Server (NTRS), NONLINEAR PROGRAMMING, NEURAL NETS, AIRCRAFT DESIGN, NATIONAL...

The Flight-Optimization-System (FLOPS) code encountered difficulty in analyzing a subsonic aircraft. The limitation made the design optimization problematic. The deficiencies have been alleviated through use of neural network and regression approximations. The insight gained from using the approximators is discussed in this paper. The FLOPS code is reviewed. Analysis models are developed and validated for each approximator. The regression method appears to hug the data points, while the neural...

Topics: NASA Technical Reports Server (NTRS), AIRCRAFT DESIGN, DESIGN OPTIMIZATION, NEURAL NETS,...

A comparative study was carried out to determine the accuracy of finite element analyses based on the stiffness method, a mixed method, and the new integrated force and dual integrated force methods. The numerical results were obtained with the following software: MSC/NASTRAN and ASKA for the stiffness method; an MHOST implementation method for the mixed method; and GIFT for the integrated force methods. The results indicate that on an overall basis, the stiffness and mixed methods present some...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, FINITE ELEMENT METHOD, MATHEMATICAL...

The Integrated Force Method has been developed in recent years for the analysis of structural mechanics problems. This method treats all independent internal forces as unknown variables that can be calculated by simultaneously imposing equations of equilibrium and compatibility conditions. In this paper a finite element library for analyzing two-dimensional problems by the Integrated Force Method is presented. Triangular- and quadrilateral-shaped elements capable of modeling arbitrary domain...

Topics: NASA Technical Reports Server (NTRS), FINITE ELEMENT METHOD, STRUCTURAL ANALYSIS, STRESS...

A research project to comparatively evaluate 10 nonlinear optimization algorithms was recently completed. A conclusion was that no single optimizer could successfully solve all 40 problems in the test bed, even though most optimizers successfully solved at least one-third of the problems. We realized that improved search directions and step lengths, available in the 10 optimizers compared, were not likely to alleviate the convergence difficulties. For the solution of those difficult problems we...

Topics: NASA Technical Reports Server (NTRS), MULTIDISCIPLINARY DESIGN OPTIMIZATION, ALGORITHMS, AIRCRAFT...

Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, FINITE ELEMENT METHOD, SMART...

The strain formulation in elasticity and the compatibility condition in structural mechanics have neither been understood nor have they been utilized. This shortcoming prevented the formulation of a direct method to calculate stress. We have researched and understood the compatibility condition for linear problems in elasticity and in finite element analysis. This has lead to the completion of the method of force with stress (or stress resultant) as the primary unknown. The method in elasticity...

Topics: NASA Technical Reports Server (NTRS), COMPATIBILITY, DESIGN OPTIMIZATION, ELASTIC PROPERTIES,...

Several nonlinear mathematical programming algorithms for structural design applications are available at present. These include the sequence of unconstrained minimizations technique, the method of feasible directions, and the sequential quadratic programming technique. The optimality criteria technique and the fully utilized design concept are two other structural design methods. A project was undertaken to bring all these design methods under a common computer environment so that a designer...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, COMPUTER PROGRAMS, DESIGN ANALYSIS, FINITE...

A general purpose optimization tool for multidisciplinary applications, which in the literature is known as COMETBOARDS, is being developed at NASA Lewis Research Center. The modular organization of COMETBOARDS includes several analyzers and state-of-the-art optimization algorithms along with their cascading strategy. The code structure allows quick integration of new analyzers and optimizers. The COMETBOARDS code reads input information from a number of data files, formulates a design as a set...

Topics: NASA Technical Reports Server (NTRS), NONLINEAR PROGRAMMING, MULTIDISCIPLINARY DESIGN OPTIMIZATION,...