T&P Seminar – Modeling the mechanical response of polycrystalline systems based on new

Details

Modeling the mechanical response of polycrystalline systems based on new single crystal constitutive models

Tuesday, August 18, 2022, at 12:50 pm
Location: MAE-A 303

Dr. Benoit Revil-Baudard
Assistant Research Scientist
Department of Mechanical & Aerospace Engineering
University of Florida

Abstract

During a hypersonic operation, there is potential for extreme thermal loading during flight and severe impact loading during penetration which may lead to adverse transformations of the energetics payload. Even though the overall (bulk) temperature of the energetic system is too low to ignite, local peaks in temperature could induce partial burn, which may result in non-ideal functioning of the payload, e.g., much of the explosive remains either unreacted or partially burnt.
In this talk are presented very recent theoretical and computational capabilities developed to respond to the need to realistically predict the large-scale thermo-mechanical response of energetic materials under dynamic loadings. The key idea behind these efforts is that a realistic description of the response of the payload can be achieved only if the crystallinity of the energetic systems and most importantly, the specific anisotropy in the plastic flow of the constituent crystals are accurately modeled. A new single-crystal model that accounts for intrinsic symmetries associated to the crystal lattice and a new computationally efficient framework for the description of the aggregate system response has been developed. Specifically, with this newly developed framework, the orientation, plastic strains, and stresses in the individual grains are continuously updated, so the predicted macroscopic scale response accounts for the evolution of the thermo-mechanical state at the lower scale.
The application of this computational model is illustrated by simulating the response of a pentaerythritol tetranitrate (PETN) polycrystalline high energetic system when subjected to high strain rate loadings. Strong differences in temperature and stresses between the constituent grains, depending on their relative orientation with respect to the wave direction are revealed. Furthermore, the rise in temperature in certain grains may be well in excess of the overall value. 3-D FE simulations of the impact of a penetrator made of high-strength steel containing a PETN energetic system are also presented providing insights into the complex interactions between the energetic system and the metallic casing material. It is shown that if the crystallinity of the energetic system is neglected, the predicted temperature rises and the extent of the zone of maximum heating in the energetic system during the impact event differ noticeably from those obtained with the new polycrystalline model which accounts for the crystallinity of the PETN material and the anisotropy in the plastic flow of its constituent crystals.

Biography

Dr. Benoit Revil-Baudard is a research scientist in the Department of Mechanical and Aerospace Engineering at UF-REEF. He holds a MS/BS (Ingénieur Diplômé) from the Institut National des Sciences Appliquées de Lyon and a Ph.D. from Ecole des Mines de Paris. He has contributed to several areas including computational mechanics and advanced manufacturing of metallic materials and textile composites. At the UF-REEF, he has developed a research program and research laboratory devoted to the study of the response of heterogeneous materials and multi-materials systems to extreme loadings. While the focus of his research activities is on the modeling of materials and structures, he has developed and designed innovative experimental capabilities and provided technology solutions to the defense sector. His research has received continued support both from AFOSR and the US Air Force Research Laboratory Munitions Directorate. He has co-authored 2 books, co-edited one book, and authored or co-authored over 50 refereed papers. In the past 10 years, he has delivered invited and keynote lectures at major conferences in the field. He has been active in co-organizing topical symposia and promoting international research collaborations.

MAE Faculty Host: Peter Ifju