A Multi-Physics Approach to Validation of Failure Models in Extreme Thermoacoustic Environments
Abstract
Failure of thin aerospace panels in the hypersonic environment has posed as a complex problem to researchers and vehicle designers in recent decades. Prior work has highlighted the complicated resonant behavior of simple structures in a combined loading environment ofvibration and heating. The effects of various heating distributions on pre-thermally buckled and post-thermally buckled plates have been evaluated in theoretical and experimental work. Fatigue failure caused by in-plane thermal gradients from localized heating, vibration, and mechanical boundary conditions has not been well addressed in the laboratory setting. The present work adds to current understanding of this topic with a series of experiments which investigate structural response and failure at multiple length scales. Thin aerospace-type beams and plates made of a nickel super-alloy, Hastelloy X, and of 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 06, 2019
- Accession Number
- AD1097227
Entities
People
- John Lambros
Organizations
- University of Illinois Urbana–Champaign