University of Illinois Urbana-Champaign

Multiscale characterization of thermoacoustic response and fatigue failure of aerospace structures

Ding, Arthur Bowen

Content Files
DING-THESIS-2018.pdf

Permalink

https://hdl.handle.net/2142/101614

Description

Title
Multiscale characterization of thermoacoustic response and fatigue failure of aerospace structures
Author(s)
Ding, Arthur Bowen
Issue Date
2018-07-18
Director of Research (if dissertation) or Advisor (if thesis)
Lambros, John
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2018-09-27T16:17:58Z
Keyword(s)
Fatigue, Failure, Aerospace
Abstract
Sustained hypersonic flight has presented a complex problem to researchers and structural designers in recent decades as it has been seen to induce failure of thin aerospace panels in modes that had not been previously accounted for. These new and unaccounted for failure modes are attributed to the extreme and coupled loading conditions of the thermoacoustic environment prevalent in hypersonic flight. Prior research has highlighted the resonant behavior of simple structures in a combined loading environment of vibration and heating. The effects of various heating distributions on pre-thermally and post-thermally buckled plates have been evaluated in theoretical and experimental work. However, this understanding has not yet found its way into advanced thermomechanical coupled simulations, in part because fatigue failure caused by in-plane thermal gradients from localized heating, vibration, and mechanical boundary conditions has not been sufficiently addressed in the laboratory setting to validate such complex simulations. The present work seeks to add to our current understanding of this topic with a series of experiments which investigate structural response and failure at multiple length scales. Non-contact optical methods for displacement and strain measurement were used to study the resonance, broadband excitation response, and thermal loading response of structures with varying boundary conditions. Thin aerospace-type beams and plates made of a nickel super-alloy, Hastelloy X, Al 1100-O, and Al 1100-H14 were subjected to forced vibration initially at room temperature and subsequently with localized heating to examine the effects of thermal stress gradients on structural response. Coarse-grained specimens were then produced by annealing aluminum Al 1100-O (commercially pure Al) to explore the role of microstructural phenomena in the thermoacoustic environment and their influences on global behavior. Using oligocrystal samples in this fashion made the grain scale effects occur at the same scale as the sample size and thus both effects could be investigated simultaneously. The microstructural heterogeneity of coarse-grained beams was shown to have significant effect on plastic hinging behavior at the beam root. Finally, fatigue experiments were performed in a combined loading environment to assess behavior beyond the linear elastic regime and promote plasticity and failure. Although fatigue failure was suppressed in thin beams and panels, adding a stress concentrator, such as a notch near the beam root, promoted fatigue crack nucleation.
Graduation Semester
2018-08
Type of Resource
text
Permalink
http://hdl.handle.net/2142/101614
Copyright and License Information
Copyright 2018 Arthur Ding

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois
Dissertations and Theses - Aerospace Engineering