A Kiley

On the use of SEREP for satellite FEM validation

Purpose – The purpose of this paper is to assess the suitability of various methods for the reduction of a large finite element model (FEM) of satellites to produce models to be used for correlation of the FEM with test results. The robustness of the cross‐orthogonality checks (COC) for the correlation process carried out utilizing the reduced model is investigated, showing its dependence on the number of mode shapes used in the reduction process. Finally the paper investigates the improvement in the robustness of the COC that can be achieved utilizing optimality criteria for the selection of the degrees of freedom (DOF) used for the correlation process.Design/methodology/approach – A Monte Carlo approach has been used to simulate inaccuracies in the mode shapes (analysis and experimental) of a satellite FEM that are compared during the COC. The sensitivity of the COC to the parameters utilized during the reduction process, i.e. mode shapes and DOFs, is then assessed for different levels of inaccuracy in ...

Model Reduction and Sensor Placement Methods for Finite Element Model Correlation

The issue of model reduction is one that must often be overcome in order to perform the necessary checks as part of the spacecraft finite element model validation process. This work compares different reduction methods: specifically, the popular and longstanding Guyan method and the potentially more accurate system equivalent reduction expansion process. The influence of sensor set location on the quality of the reduced model is also considered, and the commonly applied methods to maximize kinetic energy and effective independence are applied. These investigations take the form of studies involving two large, unique, scientific spacecraft. The computational results are compared with experimental results that are also detailed in the paper. The findings highlight the potential issues with the accuracy of a Guyan reduced model in replicating the full system dynamics, even with a reasonably large sensor set. It is shown that this can be improved slightly in some circumstances through implementation of sensor...

Study of Correlation Criteria for Spacecraft-Launch Vehicle Coupled Loads Analysis

In spacecraft structural verification, Coupled Loads Analyses (CLAs) use Finite Element Models (FEMs) of the spacecraft and launch vehicle to predict flight loads. It is therefore essential that the spacecraft FEMs to be used in these CLAs are first validated through comparison with test measured data. This study has been conducted in order to assess the metrics/criteria used to quantify the level of correlation between the analytical model and physical spacecraft test structure. To explore this, both baseline spacecraft FEM and altered versions (generated by introducing errors to the baseline) have been subjected to the same loading scenarios. Differences in response between the baseline and ‘perturbed’ models have been observed. Various correlation criteria, such as modal assurance criteria and cross-orthogonality checks, and a lesser-known comparison of base forces, have been applied to quantify the level of correlation between each altered model and its corresponding baseline FEM. The results indicate that the more popular modal vector correlation methods may not be the most effective at predicting the level of error in peak displacement responses, and that the base force criteria, known as BFAC, may be more sensitive to changes in these responses.