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Daniel Guggenheim School of Aerospace Engineering

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search.filters.applied.f.advisor: Rimoli, Julian J. × End date: 2022 × Start date: 2020 × search.filters.applied.f.isOrgUnitOfPublicationTitle: College of Engineering ×

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Now showing 1 - 5 of 5
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Physics enabled Data-driven structural analysis for mechanical components and assemblies

2022-05-20 , Shah, Aarohi Bhavinbhai

Analyzing structures that exhibit nonlinear and history-dependent behaviors is crucial for many engineering applications such as structural health monitoring, wave management/isolation, and geometric optimization to name a few. However, current approaches for modeling such structural components and assemblies rely on detailed finite element formulations of each component. While finite element method serves to be versatile and well-established for nonlinear and history-dependent problems, it tends to be inefficient. Consequently, their computational cost, becomes prohibitive for many applications when time-sensitive predictions are needed. In the present work, we introduce a framework to develop data-driven dimensionally-reduced surrogate models at the component level, which we call smart parts (SPs), to establish a direct relationship between the input–output parameters of the component. Our method utilizes advanced machine learning techniques to develop SPs such that all the information pertaining to history and nonlinearities is preserved. Unlike other data-driven approaches, our method is not limited to any particular type of nonlinearity and it does not impose restrictions on the type of analysis to be performed. This renders its application straightforward for a diverse set of engineering problems, as we show through multiple case studies. We also propose a novel meta learning based approach to enable an extension of this approach to dynamic problems. In addition, we present several ways to enhance this approach in terms of precision and efficiency. Thus, the present work provides an approach that can dramatically boost the computational efficiency and simplicity to analyze large structures without sacrificing accuracy.

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Additive Manufacturing of Compliant Mechanisms for Deployable Aerospace Structures

2021-04-27 , Gebara, Christine

In the past 10 years, complex deployable structures have become common on JPL CubeSats (e.g. RainCube, MARCO, ISARA) and large-scale spacecraft (e.g. SMAP, SWOT, NISAR, Starshade). As new, ambitious missions are pursued, there is an increased need for more mass and volume efficient deployments (higher packing density). Over the same timeframe, additive manufacturing (AM) has enabled the fabrication of new forms of flight hardware including the PIXL instrument structure, the Moxie instrument, and the RainCube antenna structure. However, AM of compliant mechanisms has not been leveraged to design deployable space structures. AM of compliant mechanisms within deployable structures (e.g. antennas, solar panels, booms), could drastically lower part counts, create novel structural tuning methods, and design previously impossible geometries. Utilizing AM would therefore lead to deployable spacecraft elements with higher mass and volume efficiencies. AM of compliant mechanisms (4D printing) is an active research area. The ability to print these mechanisms in polymers has been demonstrated. However, metal 4D-printing is still a maturing technology for aerospace applications. One area of interest is additive manufacturing of flexure hinges for flat reflectarray antennas, radiators, and solar panels. Another application is the ability to print structurally embedded spring elements that are geometrically tuned for a specific deployable structure. This could result in numerous benefits. Primarily, embedding compliant mechanisms directly where they are used would simplify deployment dynamics, thus also simplifying the characterization and control of the deployment. Second, printing structurally embedded compliant elements could enable systems that are otherwise impossible to assemble or manufacture. For example, the ability to print a structurally embedded torsional spring within the hinge mechanisms for a SWOT-type deployable mast could ease manufacturing problems, decrease part count, decrease mechanism shimming, and improve reliability.

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A plasma-wall interaction model for the erosion of materials under ion bombardment

2022-04-20 , Logarzo, Hernan Javier

Understanding the evolution and behavior of materials exposed to plasma is critical for the design of future electric propulsion devices. As ions are ejected from the device generating thrust, they also impact the ceramic walls. This induces wall erosion, ultimately exposing the magnetic circuit leading to malfunction and failure of the device. This problem is only going to be amplified as the field moves towards high power density devices. There are several models that try to predict this effect by accounting for material sputtering. However, they cannot predict the millimeter-scale surface features that develop after prolonged exposure. In this work, we address this issue by introducing a plasma-material interaction model able to capture the evolution of surface features at the macroscopic scale on materials exposed to plasma over a long period of time. The model is based on (i) data from plasma dynamics simulations, (ii) a probability model of erosion, (iii) geometric effects to account for shadowing effects and feature size and (iv) a continuum finite element model for the thermo-mechanical response of the dielectric walls that uses machine learning to account for the complex response of the material. Results show that the model is able to reproduce not only the mean erosion rate but also the macroscopic anomalous ridges that appear after prolonged exposure. Furthermore, it highlights the need to account for complex thermo-mechanical material behavior to be able to explain such features.

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Structural impacts of inflatable aerodynamic decelerator design

2020-05-17 , Li, Lin

In order to land larger payloads to Mars, more capable decelerators are required to advance beyond the performance limitations of traditional heritage entry, descent, and landing technologies. One potential technology is an inflatable aerodynamic decelerator (IAD), a flexible aeroshell that can be folded and stowed in a rocket fairing during launch and inflated prior to entry. IADs allow for larger drag areas with minimal mass increase in comparison to traditional rigid aeroshells and, thus, enable improved deceleration performance. However, minimal insight is available regarding the impact of detailed IAD configuration design on their structural performance. Future missions involving IADs will require this structural performance information early in the design cycle in order to develop IADs that have favorable structural and mass performance and are tailorable to specific mission requirements. This thesis advances the state of the art of inflatable aerodynamic decelerator design by investigating the implications of IAD configuration on their structural and mass performance and developing data analysis techniques to assess an IAD's global dynamic response. These methodologies and results improve future IAD design efforts by enabling estimates of structural performance information in conceptual design, exploring the configurational impacts of novel decelerator designs, and providing new test methodologies to better evaluate those designs. This research, therefore, starts to explore the next phases in the IAD development process, as inflatable decelerator technology maturation transitions from early-stage concept demonstration to applications on future missions that require expanded capabilities beyond the current configurational design space. In order to inform conceptual design efforts, simplified models of traditional stacked tori and tension cone decelerators are developed that strategically eliminate complexity in the IAD design to enable rapid simulation of the structural response. These computationally efficient models are used to evaluate the entire configurational design space and enable assessments of the IAD design on their structural and mass performance. A new hybrid decelerator is also developed, leveraging the benefits of the stacked tori and tension cone designs, to provide configurations that better balance mass efficiency with reduced deflection compared to the traditional stacked tori and tension cone designs. New data analysis methodologies are also developed to extract information on an IAD’s dynamic response from photogrammetry data. These methodologies allow for visualization of the global IAD dynamic response along with an evaluation of the frequency content of motion. The analysis routines are applied to existing photogrammetry data sets to highlight fundamental characteristics of the decelerator dynamic response and fluid-structure resonance phenomena.

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A Micromechanically-Informed Model of Thermal Spallation with Application to Propulsive Landing

2021-12-15 , Hart, Kenneth Arthur

During the propulsive landing of spacecraft, the retrorocket exhaust plume introduces the landing site surface to significant pressure and heating. Landing site materials include concrete on Earth and bedrock on other bodies, two highly brittle materials. During a landing event, defects and voids in the material grow due to thermal expansion and coalesce, causing the surface to disaggregate or spall. After a spall is freed from the surface, the material beneath it is exposed to the pressure and heat load until it spalls, continuing the cycle until engine shutdown. Spalls and debris entrained in the exhaust plume risk damaging the lander or nearby assets- a risk that increases for larger engines. The purpose of this work is to develop a micromechanically-informed model of thermal spallation to improve understanding of this process, in the context of propulsive landing. A preliminary simulation of landing site spallation, utilizing an empirical thermal spallation model, indicates that spallation may occur for human-scale Mars landers. This model, however, was developed for drilling through granite, which has a fundamentally different microstructure compared to typical landing sites, necessitating a more general approach. To that end, highly-detailed simulations of thermomechanical loading, applied to representative microstructures, inform a functional relationship between applied heat flux and spallation rate. These representative microstructures can be generated using an algorithm that has been validated for a wide variety of materials, including basalt from Gusev Crater, Mars.

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