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Flight environments demonstrator: Part I—experiment design and test planning

Conference Proceedings of the Society for Experimental Mechanics Series

Owens, Brian C.; Mayes, R.L.; Khan, Moheimin Y.; Tipton, David G.; Zwink, Brandon R.

Flight testing provides an opportunity to characterize a system under realistic, combined environments. Unfortunately, the prospect of characterizing flight environments is often accompanied by restrictive instrumentation budgets, thereby limiting the information collected during flight testing. Instrumentation selection is often a result of bargaining to characterize environments at key locations/sub-systems, but may be inadequate to characterize the overall environments or performance of a system. This work seeks to provide an improved method for flight environment characterization through a hybrid experimental-analytical method, modal response extraction, and model expansion. Topics of discussion will include hardware design, assessment of hardware under flight environments, instrumentation planning, and data acquisition challenges. Ground testing and model updating to provide accurate models for expansion will also be presented.

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TYPE Conference Poster YEAR 2020
ScopusOSTIDOI

Methods for component mode synthesis model generation for uncertainty quantification

Conference Proceedings of the Society for Experimental Mechanics Series

Brink, Adam R.; Tipton, David G.; Freymiller, J.E.; Stevens, B.L.

Component mode synthesis (CMS) is a widely employed model reduction technique used to reduce the computational cost associated with the dynamic analysis of complex engineering structures. To generate CMS models, specifically the formulation of Craig and Bampton, both normal fixed-interface modes and constraint modes of the component’s structure are calculated. These modes are used in conjunction with the component level mass and stiffness matrices to generate reduced mass and stiffness matrices used in the final analyses. For some component models, the most computationally expensive part of this procedure is calculating the component normal modes information. Several different approaches are utilized to investigate the sensitivity of system level responses to variations in several aspects of the CMS models. One approach evaluates changes due to modifications of the reduced mass and stiffness matrices assuming that the mode shapes do not change. The second approach assumes that the mode shapes change but the reduced mass and stiffness matrices do not change. An example is presented to show the influence of these two approaches.

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TYPE Conference Poster YEAR 2017
ScopusOSTIDOI

6-DOF shaker test input derivation from field test

Conference Proceedings of the Society for Experimental Mechanics Series

Ross, Michael R.; Jacobs-O'Malley, Laura D.; Tipton, David G.; Nelson, Garrett D.; Cross, Kevin R.; Hunter, Norman H.; Harvie, Julie M.

Six degree of freedom (6-DOF) subsystem/component testing is becoming a desirable method, for field test data and the stress environment can be better replicated with this technology. Unfortunately, it is a rare occasion where a field test can be sufficiently instrumented such that the subsystem/component 6-DOF inputs can be directly derived. However, a recent field test of a Sandia National Laboratory system was instrumented sufficiently such that the input could be directly derived for a particular subsystem. This input is compared to methods for deriving 6-DOF test inputs from field data with limited instrumentation. There are four methods in this study used for deriving 6-DOF input with limited instrumentation. In addition to input comparisons, response measurements during the flight are compared to the predicted response of each input derivation method. All these methods with limited instrumentation suffer from the need to inverse the transmissibility function.

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TYPE Conference Poster YEAR 2017
ScopusOSTIDOI

Structural-acoustic mode coupling in a bolted aluminum cylinder

Conference Proceedings of the Society for Experimental Mechanics Series

Pacini, Benjamin R.; Tipton, David G.

This work presents a modal test on a cylindrical bolted structure that initially appeared to be a routine model calibration experiment. However, while reviewing the test data the structure appeared to have two pairs of ovaling modes with identical shapes. Assuming this to be the result of an uninstrumented component of the test article, extensive efforts were conducted to identify this feature. When all options were exhausted, the interaction between the structure and the air contained within was investigated. Contrary to the typical assumption that the fluid-structure interactions are negligible for such a thick walled cylinder, analysis showed that for this test article the acoustic modes of the internal air significantly impacted the structural response. In this case, the acoustic and the structural modes coincided in frequency, causing the first ovaling modes to split into two pairs at different frequencies. Experimental and analytical results are presented that describe this structural-acoustic mode coupling phenomenon.

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TYPE Conference Poster YEAR 2016
ScopusOSTIDOI
Results 1–25 of 42
Results 1–25 of 42