An automated technique for improving model matrices by means of experimentally obtained dynamic data

Truong

2015

Journal of Aircraft

Small modeling errors in a finite-element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the X-56A Multi-Utility Technology Testbed aircraft is the flight demonstration of active flutter suppression and, therefore, in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground-vibration test-validated structural dynamic finite-element model of the X-56A aircraft is created in this study. The structural dynamic finite-element model of the X-56A aircraft is improved using a model-tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, whereas other properties such as c.g. location, total weight, and off-diagonal terms of the mass orthogonality matrix were used as constraints. The end result was an improved structural dynamic finite-element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.

mentioning

confidence: 99%

Creating a Test-Validated Finite-Element Model of the X-56A Aircraft Structure

Truong

2015

Journal of Aircraft

Finite Element Model Tuning Using Measured Mass Properties and Ground Vibration Test Data

Journal of Vibration and Acoustics

2009

A simple and efficient approach for tuning finite element models to match computed frequencies, mode shapes, and mass properties to the experimental data is introduced in this study. The model tuning procedure proposed in this study is based on a series of optimizations. This approach has been successfully applied to create an equivalent beam finite element model for the X-37 drogue chute test fixture with the X-planes pylon. The goal was a simple model capable of being analyzed in a captive carry configuration with the B-52H mother ship. This study has shown that natural frequencies, corresponding mode shapes, and mass properties from the updated finite element model achieved at the final optimization iteration have excellent agreement with corresponding measured data.

Finite Element Model Tuning Using Analytical Sensitivity Values

2023

Journal of Aircraft

This paper presents an efficient approach for tuning finite element models to match the measured ground vibration test and proof test data. Frequencies, mode shapes, total weight, location of the center of gravity, and static deformation computed from the finite element model are matched to the measured data. The model tuning procedure used in this work is based on solving an optimization problem in which the errors for the considered metrics, between the finite element prediction and the measured data, are minimized. Analytical sensitivity values of performance indices are computed using the NASTRAN-generated sensitivity values together with the in-house computer programs, which allow for faster computational time and the use of gradient-based optimizers. The method is applied to the Aerostructures Test Wing 4 model. The study shows that the military standard and the NASA standard for comparing analytical and experimental modal data are all satisfied. The final finite element model correlates well with the test data. The flutter speed decreases by 8.91% after model tuning compared with the original Aerostructures Test Wing 4 design.