Collaborative Center for Structural Science

Per the Broad Agency Announcement, the exact delineation of the work to be carried out as part of the center effort will be decided jointly by the Air Force Research Lab Structural Science Center (AFRL/SSC) members and the OSU-led team members during the kick-off meeting. Nevertheless, the tasks stated below represent the current best perspective on the work to be carried out by ASU. ASU will contribute to both Thrusts 1 and 2 of the proposal performing the following tasks. (1) Development and validation of a full coupling between the currently available structuralthermal reduced order models (ROM) and aerodynamic prediction tools, either full computational fluid mechanics (CFD) or ROM. The CFD implementation will serve as the baseline for the validation of the aerodynamic ROM implementation. This effort should include aero-structural and aero-thermal feedback mechanisms. (2) Extension of the thermal ROM to (i) include temperature dependent thermal properties as well as (ii) the effects of large structural deformations as they modify the geometry over which the thermal problem is solved. An investigation of this effect will be carried out on a particular panel to assess its magnitude and characteristics. (3) Formulation, development, and validation of an extension of the structural ROM strategy that accounts for local plastic deformations. It is anticipated to achieve this extension by modeling the plastic strains as equivalent body forces. This extension will permit the better capturing of the response of panels with sharp notches (cracks) or exhibiting local buckling inducing local yielding. (4) Owing to the high temperatures, it is planned to extend further the methodology to account for creep over the global structure. Such an inclusion, as well as that of plastic strains, have never been proposed in linear modal models let alone nonlinear structural ROMs. (5) A significant effort will be focused on multiscale reduced order modeling methods considering first the accurate capture of the local stress distribution induced by notches and cracks. It is planned for this effort to develop a close coupling between the reduced order model construction strategy and the Generalized Finite Element Method (GFEM) to have a highly accurate basis. At this point, it is anticipated that the validation of this approach will be performed on the Lockheed cracked panel. (6) Multiscale methods will be further developed to upscale the ROM approaches to full vehicle. AFOSR funded efforts in this direction are on-going at ASU and have provided deep insight into the local and global character of the nonlinear geometric structural response. Yet, significant efforts will be necessary to render such approaches computationally attractive. A key difficulty is the curse of dimensionality that arises as the complexity of the structure is increased and is reflected by a rapidly growing basis and its associated ROM parameters. To solve this issue, it is in particular proposed to proceed with homogenizations of the structural details and establish global ROMs, both structural and thermal, that permits a good first prediction of the response/temperature at the global/vehicle level. This information will then be transferred to the component level through appropriate boundary conditions. The component level ROMs will then provide the accurate prediction necessary. (7) Close collaborations with Ohio State University, Johns Hopkins University, and the 4th team member will be critical and thus a continuous task will be the support of the other team members in all activities relating to the tasks above as well as their own.