Joseph A. Beck

Orbit Estimation of a Continuously Thrusting Spacecraft Using Variable Dimension Filters

The Center for Space Research and Assurance at the U.S. Air Force Institute of Technology investigates short-term tactical spacecraft missions that require frequent maneuvers. An important part of this research is developing methods of performing orbit determination on noncooperative spacecraft that maneuver often at unknown times with unknown thrusts. When a spacecraft performs long-duration thrusts in view of radars, traditional orbit determination, and batch least-squares routines are ineffective methods of fitting the orbit. Adaptive variable-state dimension filters allow for accurate orbit and thrust acceleration estimation during long-duration maneuvers. This work develops and evaluates routines that use both an extended and unscented augmented state Kalman filter along with interacting multiple models to estimate maneuvers. Several methods are evaluated to determine the start and conclusion of continuous maneuvers, and a multiple-model approach is introduced to determine the conclusion of low-thrus...

Uncertainties of an Automated Optical 3D Geometry Measurement, Modeling, and Analysis Process for Mistuned Integrally Bladed Rotor Reverse Engineering

An automated reverse engineering process is developed that uses a structured light optical measurement system to collect dense point cloud geometry representations. The modeling process is automated through integration of software for point cloud processing, reverse engineering, solid model creation, grid generation, and structural solution. Process uncertainties are quantified on a calibration block and demonstrated on an academic transonic integrally bladed rotor. These uncertainties are propagated through physics-based models to assess impacts on predicted modal and mistuned forced response. Process details are discussed and recommendations made on reducing uncertainty. Reverse engineered parts averaged a deviation of 0.0002 in. (5 μm) which did not significantly impact low and midrange frequency responses. High frequency modes were found to be sensitive to these uncertainties demonstrating the need for future refinement of reverse engineering processes.

Parameter Requirements for Noncooperative Satellite Maneuver Reconstruction Using Adaptive Filters

The Responsive Orbits division of the Center for Space Research and Assurance in the Aeronautics and Astronautics Department of the Air Force Institute of Technology investigates short-term tactical satellite missions that require frequent maneuvers. Pairing research in designing and conducting avoidance maneuvers with research in detecting and tracking maneuvering satellites sets the stage for developing and improving both areas. Strategies in stochastic filtering, smoothing, multiple model adaptive estimation, and maneuver reconstruction are developed to track a high-priority satellite. The article develops a wide range of simulations that modify the maneuver type, tracking antenna performance, antenna coverage, reconstruction method, filtering approach, and number of postmaneuver passes collected. The results determine the levels of error covariance necessary to perform successful maneuver reconstructions. Additionally, the results provide maneuver reconstruction confidence percentages based on the est...

Probabilistic Mistuning Assessment Using Nominal and Geometry Based Mistuning Methods

Two deterministic mistuning models utilizing component mode synthesis methods are used in a Monte Carlo simulation to generate mistuned response distributions for a geometrically perturbed Integrally Bladed Rotor. The first method, a frequency-perturbation approach with a nominal mode approximation used widely in academia and industry, assumes airfoil geometric perturbations alter only the corresponding modal stiffnesses while its mode shapes remain unaffected. The mistuned response is then predicted by a summation of the nominal modes. The second method, a geometric method utilizing non-nominal modes, makes no simplifying assumptions of the dynamic response due to airfoil geometric perturbations, but requires recalculation of each airfoil eigen-problem. A comparison of the statistical moments of the mistuned response distributions and prediction error is given for three different frequency ranges and engine order excitations. Further, the response distributions are used for a variety of design and testing scenarios to highlight impacts of the frequency-based approach inaccuracy. Results indicate the frequency-based method typically provides conservative response levels.Copyright

Automated Finite Element Model Mesh Updating Scheme Applicable to Mistuning Analysis

Advancement of optical geometric measurement hardware has enabled the construction of accurate 3D tessellated models for a wide range of turbomachinery components. These tessellated models can be reverse-engineered into computer-aided design (CAD) models and input into grid generation software for finite element analyses. However, generating a CAD model from scan data is a time consuming and cumbersome process requiring significant user-involvement for even a single model. While it is possible to generate finite element models (FEMs) directly from tessellated data, current direct-grid methods produce unstructured grids that can introduce fictitious, numerical mistuning in these models, obscuring geometric mistuning. Nonetheless, as-measured scan data captured in a structured grid is essential for accurate geometric mistuning analyses, provided the tessellated scan data can be rapidly and accurately transformed into a FEM. This paper outlines and demonstrates an approach for rapidly generating structured FEMs for a population of integrally bladed rotors (IBRs) without requiring the arduous task of generating a CAD model for each as-measured IBR. This is accomplished by morphing the structured mesh of a nominal model to the tessellated data set collected from an optical scanner. It is shown that the fidelity and structure of these FEMs can be utilized for accurate mistuning analyses.© 2014 ASME

Component-Mode Reduced-Order Models for Geometric Mistuning of Integrally Bladed Rotors

Two methods that explicitly model airfoil geometry surface deviations for mistuning prediction in integrally bladed rotors are developed by performing a modal analysis on different degrees of freedom of a parent reduced-order model. The parent reduced-order model is formulated with Craig–Bampton component-mode synthesis in cyclic symmetry coordinates for an integrally bladed rotor with a tuned disk and airfoil geometric deviations. The first method performs an eigenanalysis on the constraint-mode degrees of freedom that provides a truncated set of interface modes, whereas the second method includes the disk fixed-interface normal mode in the eigenanalysis to yield a truncated set of ancillary modes. Both methods can use tuned or mistuned modes, where the tuned modes have the computational benefit of being computed in cyclic symmetry coordinates. Furthermore, the tuned modes only need to be calculated once, which offers significant computational savings for subsequent mistuning studies. Each geometric mist...

Material Property Determination of Vibration Fatigued DMLS and Cold-Rolled Nickel Alloys

An experimental procedure for qualifying material properties from cyclically worked parts was investigated in support of aging gas turbine engines and digital twin initiatives. For aging components, remanufacturing or repair efforts are necessary to sustain the life cycles of engines; and for digital twin, the virtual representation of a part requires accurate geometric and component material property measurement. Therefore, having an effective, non-destructive way to assess the material performance of parts is necessary. Since low cycle, low strain, mechanical testing is the ideal experimental approach for non-destructively assessing material properties, investigating the accuracy and trends of tensile properties of fatigue loaded parts was important. The fatigued parts used for this study were specimens tested according to the George Fatigue Method, and the materials observed were cold-rolled Inconel Alloys 625 and 718, and direct metal laser sintering (DMLS) Nickel Alloy 718. The tensile material properties were compared against pristine (non-fatigued) and published data. The comparison for the cold-rolled 625 and 718 results show an increase and a decrease, depending on rolling direction, of tensile strength due to the effects of fatigue cycles; however, the variation of the vibration affected tensile properties are all within one standard deviation of the pristine data. The comparisons of DMLS Nickel Alloys was conducted against two sets of alloys from different suppliers, and the results showed that the tensile properties are sensitive to DMLS manufacturing parameters and post-sintering processes. A digital twin related, nondestructive, material property determination technique is also discussed in this manuscript. The true alloy density was determined with the water displacement method, and elastic modulus is determined with an iterative Ritz method model. The modulus is under-predicted with this method, but suggestions for improving the model are discussed.Copyright

Regression Study to Standardize Piezoelectric Axial Fatigue Testing

A hierarchical Bayesian approach is used to investigate the influence of test variables on a piezoelectric, ultrasonic axial fatigue setup. Motivation behind this investigation is two-fold: timely empirical characterization of high cycle fatigue (HCF) life would be ideal for structural assessment of critical turbine engine components; and a standardized method to control and optimize high rate cyclic loading is necessary for certified fatigue life characterization. The variables observed in this study describe forced response amplitude, material lot, test duration, test approach, specimen fastening interface, and excitation controls. Of the 12 test variables observed, five proved to have significant influence on experimental fatigue results of 54 Aluminum 6061-T6 dogbone specimens. These findings are instrumental for optimization and standardization of ultrasonic fatigue testing and empirical HCF assessment.

Framework for Creating Digital Representations of Structural Components Using Computational Intelligence Techniques

A framework for creating a digital representation of physical structural components is investigated. A model updating scheme used with an artificial neural network to map updating parameters to the error observed between simulated experimental data and an analytical model of a turbine-engine fan blade. The simulated experimental airfoil has as-manufactured geometric deviations from the nominal, design-intent geometry on which the analytical model is based. The manufacturing geometric deviations are reduced through principal component analysis, where the scores of the principal components are the unknown updating parameters. A range of acceptable scores is used to devise a design of computer experiments that provides training and testing data for the neural network. This training data is composed of principal component scores as inputs. The outputs are the calculated errors between the analytical and experimental predictions of modal properties and frequency-response functions. Minimizing these errors will...

Uncertainties of an Automated Optical 3D Geometry Measurement, Modeling, and Analysis Process for Mistuned IBR Reverse Engineering

An automated reverse engineering process is developed that uses a structured light optical measurement system to collect dense point cloud geometry representations. The modeling process is automated through integration of software for point cloud processing, reverse engineering, solid model creation, grid generation, and structural solution. Process uncertainties are quantified on a calibration block and demonstrated on an academic transonic integrally bladed rotor. These uncertainties are propagated through physics-based models to assess impacts on predicted modal and mistuned forced response. Process details are discussed and recommendations made on reducing uncertainty. Reverse engineered parts averaged a deviation of 0.0002 in. (5 μm) which did not significantly impact low and mid-range frequency responses. High frequency modes were found to be sensitive to these uncertainties demonstrating the need for future refinement of reverse engineering processes.© 2013 ASME