45,085 research outputs found

    Design Spectrum Analysis in NASTRAN

    Get PDF
    The utility of Design Spectrum Analysis is to give a mode by mode characterization of the behavior of a design under a given loading. The theory of design spectrum is discussed after operations are explained. User instructions are taken up here in three parts: Transient Preface, Maximum Envelope Spectrum, and RMS Average Spectrum followed by a Summary Table. A single DMAP ALTER packet will provide for all parts of the design spectrum operations. The starting point for getting a modal break-down of the response to acceleration loading is the Modal Transient rigid format. After eigenvalue extraction, modal vectors need to be isolated in the full set of physical coordinates (P-sized as opposed to the D-sized vectors in RF 12). After integration for transient response the results are scanned over the solution time interval for the peak values and for the times that they occur. A module called SCAN was written to do this job, that organizes these maxima into a diagonal output matrix. The maximum amplifier in each mode is applied to the eigenvector of each mode which then reveals the maximum displacements, stresses, forces and boundary reactions that the structure will experience for a load history, mode by mode. The standard NASTRAN output processors have been modified for this task. It is required that modes be normalized to mass

    Experience with Free Bodies

    Get PDF
    Some of the problems that confront an analyst in free body modeling, to satisfy rigid body conditions are discussed and with some remedies for these problems are presented. The problems of detecting these culprits at various levels within the analysis are examined. A new method within NASTRAN for checking the model for defects very early in the analysis without requiring the analyst to bear the expense of an eigenvalue analysis before discovering these defects is outlined

    Remarks at the 2017 Hooding Ceremony

    Get PDF

    Transients by substructuring with DMAP

    Get PDF
    Automated substructuring in level 16 of NASTRAN was employed as a preface to the solution of a direct transient analysis. The DMAP ALTER statements written to adapt the substructuring for transient purposes are explained. Data recovery was accomplished with transfer functions. Proof of the success of the method is presented with an application to a missile structure

    Mass modeling for bars

    Get PDF
    Methods of modeling mass for bars are surveyed. A method for extending John Archer's concept of consistent mass beyond just translational inertia effects is included. Recommendations are given for various types of modeling situations

    Modeling a ball screw/ball nut in substructuring

    Get PDF
    In the particular NASTRAN application discussed here, a nut was attached to a stationary structure. The object of the analysis was to determine the vibration characteristics of the whole structure for various configurations; i.e., the evaluation of the mode shapes and frequencies when parts were moved to different mating positions. Details of the analysis are given

    Skylab

    Get PDF
    The Skylab program is presented to show the construction of the space vehicle and the facilities provided. The projects to be conducted during Skylab missions are described. The cost of the program is discussed and plans for future Skylab vehicles and missions are analyzed. Photographs of the interior of Skylab simulators are included to clarify the report

    Modeling an electric motor in 1-D

    Get PDF
    Quite often the dynamicist will be faced with having an electric drive motor as a link in the elastic path of a structure such that the motor's characteristics must be taken into account to properly represent the dynamics of the primary structure. He does not want to model it so accurately that he could get detailed stress and displacements in the motor proper, but just sufficiently to represent its inertia loading and elastic behavior from its mounting bolts to its drive coupling. Described here is how the rotor and stator of such a motor can be adequately modeled as a colinear pair of beams

    Modeling of connections between substructures

    Get PDF
    It is demonstrated here that complete checkout of a basic substructure can be done under the special circumstance of a sliding connection with offsets. Stiff bar connectors make this possible so long as the bar coordinates are aligned with the displacement coordinates at the sliding surface

    Condensing loaded points for transients by substructuring

    Get PDF
    A technique for condensing dynamic loading points is described. The method was applied to substructure transient solutions and was found to be very effective
    • …
    corecore