Ricardo A. Perez

Bio: Ricardo A. Perez is an academic researcher from Air Force Research Laboratory. The author has contributed to research in topics: Finite element method & Nonlinear system. The author has an hindex of 12, co-authored 36 publications receiving 430 citations. Previous affiliations of Ricardo A. Perez include Wright-Patterson Air Force Base & Arizona State University.

Nonlinear Reduced-Order Models for Thermoelastodynamic Response of Isotropic and Functionally Graded Panels

Abstract: The focus of this investigation is on the development and validation of thermoelastic reduced-order models for the geometrically nonlinear response and temperature of heated structures. The reduced-order modeling approach is based on a modal-type expansion of both displacements and temperatures in the undeformed, unheated configuration. A set of coupled nonlinear differential equations governing the time-varying generalized coordinates of the response and temperature expansion are derived from finite thermoelasticity using a Galerkin approach. Furthermore, the selection of the basis functions to be used in these reduced-order models is discussed, and the numerical evaluation of the model coefficients is addressed. This approach is first validated on an isotropic beam subjected to both thermal effects and external loads. The thermal effects are large enough to induce a significant buckling of the panel, while the time-varying loads lead to snap-throughs ranging in frequency from infrequent to continuous. Validation to a functionally graded material panel in similar conditions is then performed. In both cases, the reduced-order modeling predicted temperatures and responses are found to very closely match their full finite element counterparts.

Nonlinear reduced order models for thermoelastodynamic response of isotropic and fgm panels

Abstract: The focus of this investigation is on the development and validation of thermoelastic reduced order models for the geometrically nonlinear response and temperature of heated structures. The reduced order modeling approach is based on a modal-type expansion of both displacements and temperatures in the undeformed, unheated configuration. A set of coupled nonlinear differential equations governing the time varying generalized coordinates of the response and temperature expansion are derived from finite thermoelasticity using a Galerkin approach. Further, the selection of the basis functions to be used in these reduced order models is discussed and the numerical evaluation of the model coefficients is addressed. This approach is validated first on an isotropic beam subjected to both thermal effects and external loads. The thermal effects are large enough to induce a significant buckling of the panel while the time varying loads lead to snap-throughs ranging in frequency from infrequent to continuous. Validation to a functionally graded (FGM) panel in similar conditions is then performed. In both cases, the reduced order modeling predicted temperatures and responses are found to very closely match their full finite element counterparts.

Nonlinear unsteady thermoelastodynamic response of a panel subjected to an oscillating flux by reduced order models

Abstract: This paper focuses on the unsteady temperature distribution and structural response induced by an oscillating flux on the top surface of a flat panel. This flux is introduced here as a simplified representation of the thermal effects of an oscillating shock on a panel of a supersonic/hypersonic vehicle. Accordingly, a random acoustic excitation is also considered to act on the panel and the level of the thermo-acoustic excitation is assumed to be large enough to induce a nonlinear geometric response of the panel. Both temperature distribution and structural response are determined using recently proposed reduced order models (ROMs) and a complete one way, thermalstructural, coupling is enforced. A steady-state analysis of the thermal problem is first carried out that is then utilized in the structural reduced order model governing equations with and without the acoustic excitation. A detailed validation of the reduced order models is carried out by comparison with a few full finite element (Nastran) computations. The computational expedience of the reduced order models allows a detailed parametric study of the response as a function of the frequency of the oscillating flux. The nature of the corresponding structural ROM equations is seen to be of a Mathieutype with Duffing nonlinearity (originating from the nonlinear geometric effects) with external harmonic excitation (associated with the thermal moments terms on the panel). A dominant resonance is observed and explained.

Aeroelastic and Aerothermoelastic Analysis in Hypersonic Flow: Past, Present, and Future

Abstract: H YPERSONIC flight began in February 1949 when a WAC Corporal rocket was ignited from a U.S.-captured V-2 rocket [1]. In the six decades since this milestone, there have been significant investments in the development of hypersonic vehicle technologies. The NASA X-15 rocket plane in the early 1960s represents early research toward this goal [2,3]. After a lull in activity, the modern era of hypersonic research started in the mid-1980s with the National Aerospace Plane (NASP) program [4], aimed at developing a single-stage-to-orbit reusable launch vehicle (RLV) that used conventional runways. However, it was canceled due mainly to design requirements that exceeded the state of the art [1,5]. A more recent RLV project, the VentureStar program, failed during structural tests, again for lack of the required technology [5]. Despite these unsuccessful programs, the continued need for a low-cost RLV, as well as the desire of the U.S. Air Force (USAF) for unmanned hypersonic vehicles, has reinvigorated hypersonic flight research. An emergence of recent and current research programs [6] demonstrate this renewed interest. Consider, for example, the NASA Hyper-X experimental vehicle program [7], the University of Queensland HyShot program [8], the NASA Fundamental Aeronautics Hypersonics Project [9], the joint U.S. Defense Advanced Research Projects Administration (DARPA)/USAF Force Application andLaunch fromContinentalUnited States (FALCON) program [10], the X-51 Single Engine Demonstrator [11,12], the joint USAF Research Laboratory (AFRL)/Australian Defence Science and Technology Organisation Hypersonic International Flight Research Experimentation project [13], and ongoing basic hypersonic research at the AFRL (e.g., [14–20]). The conditions encountered in hypersonic flows, combined with the need to design hypersonic vehicles, have motivated research in the areas of hypersonic aeroelasticity and aerothermoelasticity. It is evident from Fig. 1 that hypersonic vehicle configurations will consist of long, slender lifting body designs. In general, the body, surface panels, and aerodynamic control surfaces are flexible due to minimum-weight restrictions. Furthermore, as shown in Fig. 2, these