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  • 1
    Publication Date: 2013-08-31
    Description: Interactive Stiffened Panel Analysis (ISPAN) modules, written in FORTRAN, were developed to provide an easy to use tool for creating finite element models of composite material stiffened panels. The modules allow the user to interactively construct, solve and post-process finite element models of four general types of structural panel configurations using only the panel dimensions and properties as input data. Linear, buckling and post-buckling solution capability is provided. This interactive input allows rapid model generation and solution by non finite element users. The results of a parametric study of a blade stiffened panel are presented to demonstrate the usefulness of the ISPAN modules. Also, a non-linear analysis of a test panel was conducted and the results compared to measured data and previous correlation analysis.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center, Third NASA Advanced Composites Technology Conference, Volume 1, Part 2; p 933-949
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: The ISPAN Program (Interactive Stiffened Panel Analysis) is an interactive design tool that is intended to provide a means of performing simple and self contained preliminary analysis of aircraft primary structures made of composite materials. The program combines a series of modules with the finite element code DIAL as its backbone. Four ISPAN Modules were developed and are documented. These include: (1) flat stiffened panel; (2) curved stiffened panel; (3) flat tubular panel; and (4) curved geodesic panel. Users are instructed to input geometric and material properties, load information and types of analysis (linear, bifurcation buckling, or post-buckling) interactively. The program utilizing this information will generate finite element mesh and perform analysis. The output in the form of summary tables of stress or margins of safety, contour plots of loads or stress, and deflected shape plots may be generalized and used to evaluate specific design.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-4449 , NAS 1.26:4449 , LG92ER0036
    Format: application/pdf
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  • 3
    Publication Date: 2019-08-28
    Description: A design for a Mars mission aerobrake with rib-stringer construction coupled with a generic shell using composite materials, which is shown to produce a feasible alternative to propulsive braking, is presented. For the case of a spherical shell subjected to a uniform pressure loading the membrane stress state is isotropic and independent of material properties. The stresses due to bending are significant and dominate only near the attachment points. The addition of meridional stiffeners increased the buckling load and absorbed a large portion of the stresses near the attachment points. The final design employed a high modulus graphite/epoxy composite material. The final weight of the structure when subjected to a 2.0 psi stagnation pressure loading was about 42,000 pounds. This constituted 9 percent of the total spacecraft weight, well below the 15 percent upper limit. It is concluded that aerobraking is a feasible alternative to a propulsive braking system. A rib-stringer shell composition coupled with composite materials is a viable configuration for an aerobrake structure.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: In: Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 1 (A93-41976 17-12); p. 873-884.
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: Non-linear analysis methods were adapted and incorporated in a finite element based DIAL code. These methods are necessary to evaluate the global response of a stiffened structure under combined in-plane and out-of-plane loading. These methods include the Arc Length method and target point analysis procedure. A new interface material model was implemented that can model elastic-plastic behavior of the bond adhesive. Direct application of this method is in skin/stiffener interface failure assessment. Addition of the AML (angle minus longitudinal or load) failure procedure and Hasin's failure criteria provides added capability in the failure predictions. Interactive Stiffened Panel Analysis modules were developed as interactive pre-and post-processors. Each module provides the means of performing self-initiated finite elements based analysis of primary structures such as a flat or curved stiffened panel; a corrugated flat sandwich panel; and a curved geodesic fuselage panel. This module brings finite element analysis into the design of composite structures without the requirement for the user to know much about the techniques and procedures needed to actually perform a finite element analysis from scratch. An interactive finite element code was developed to predict bolted joint strength considering material and geometrical non-linearity. The developed method conducts an ultimate strength failure analysis using a set of material degradation models.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-4448 , NAS 1.26:4448 , LG92ER0035
    Format: application/pdf
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