A critical task involved with being able to predict flight loads accurately in aerospace finite element models (FEMs) is the prior verification of the FEMs by conducting modal survey testing (MST). Experience comparing dynamic response of initial FEMs to MST data tends to demonstrate that FEMs can have unacceptable accuracy even when best modeling practices are followed. One inherent source of inaccuracy in linear dynamic FEMs is the modeling of nonlinear joints with mechanisms such as spherical bearings. These joints are usually designed to freely translate or rotate under the high levels of loading experienced in flight. Engineers who create linear FEMs conventionally model these joints without any stiffness in the mechanism degrees of freedom to meet this design intent. However, inaccuracy is observed during test validation of these FEMs, which usually relies on low-level force excitation orders of magnitude below flight load levels. This low-level modal test rarely overcomes the joint friction that is present, and thus the mechanism joints are able to react loads. This divide between the test results and the FEM creates a significant challenge to the engineer who is performing the correlation, in that the engineer has no basis for what stiffness value should be used to make the FEM match the test results. A compounding challenge is that complicated built-up aerospace structures commonly have multiple joints through a load path where each joint will “stick” and “slip” at different levels of force input. Explicitly matching the dynamics of a system containing these nonlinear mechanisms would require a nonlinear FEM, which is prohibitively costly for dynamic simulations of most aerospace systems. The objective of this chapter is to present a workflow that can efficiently cycle through many iterations of a FEM, allowing a Monte Carlo–style examination of the design space to identify candidate stiffness values for nonlinear mechanism joints. The outlined approach is specific to MSC Nastran and utilizes MSC Nastran’s symbolic substitution capabilities, coupled with the IMAT™ and Attune™ software packages developed by ATA Engineering, Inc. (ATA). The workflow is demonstrated with a case study from the correlation effort for The Boeing Company’s Crew Space Transportation (CST)-100 Starliner FEM.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Modal Correlation of Complex Aerospace Joints Using Automated Variable Substitution


    Additional title:

    Conf.Proceedings of Society




    Publication date :

    2022-07-31


    Size :

    14 pages





    Type of media :

    Article/Chapter (Book)


    Type of material :

    Electronic Resource


    Language :

    English




    Modal Correlation of Complex Aerospace Joints Using Automated Variable Substitution

    Winkel, James P. / Kerrian, Peter A. / Bartkowicz, Theodore J. | British Library Conference Proceedings | 2022


    Modal Correlation of an Aerospace Structure

    da Costa Moreira, André Moreno / de Barros, Everaldo / de Camargo, Leandro Ribeiro et al. | SAE Technical Papers | 2006


    Bolted Joints in Aerospace Structures

    Yay, Ömer / Kunt, Gökhan / Gürgen, Selim | Springer Verlag | 2024


    TREE JOINTS: BIOMIMETIC INSIGHTS FOR AEROSPACE COMPOSITE JOINTS

    Burns, L. / International Council of the Aeronautical Sciences; Optimage Ltd | British Library Conference Proceedings | 2010