Multiscale Modeling of Aerospace Structures subjected to Extreme Loads

Research Sponsor:

Air Force Office of Scientific Research, Multi-Scale Structural Mechanics and Prognosis. Program Director: Dr. David Stargel.

Investigators:

Shuhai (Kyle) Zhang and Caglar Oskay

Project Goal and Objectives

Goal:

Development of a simulation framework to accurately and efficiently predict elasto-viscoplastic material response, damage accumulation and failure in hypersonic structures. Bridging structural and material scale for the framework using Variational Multiscale Enrichment (VME) method is the main focus of this project.

Specific Objectives:

Develop elasto-viscoplastic computational modeling and simulation infrastructure with the ability to predict structural limit states when subjected to high temperatures, time varying and high amplitude thermal and pressure loads, and environmental exposure. An efficient multiscale enrichment methodology, taking into account the elasto-viscoplastic material behavior,for bridging the disparate structural and material scales would be developed.

Assess validity of the computational methods and models based on high-fidelity analysis methods and experimental investigations for assessment of computational efficiency so that large structural simulations are possible and reasonably accurate.

Predict damage accumulation and failure by exercising the computational framework to gain fundamental understanding of structural response when subjected to extreme thermo-mechanical environments and variable amplitude load histories.

Research Impact:

Enables design of hypersonic structures through reduction of the high knockdown factors used to compensate for the lack of knowledge of damage accumulation mechanisms.

Provides fundamental understanding of the combined and coupled effects of environmental degradation, elevated temperatures and thermo-mechanical loads on the structural survivability

Capability Development:

The ability to track microstructure damage and failure mechanisms in a structural scale analysis.

The ability to reduce the computational cost to an affordable extent while maintaining the desired accuracy.

Background and Motivation

The Air Force is actively seeking the capability to build and maintain reusable, in-atmosphere air vehicles operating at hypersonic speeds (Mach 5 and beyond).

Current design and sustainment practice: Simplified component analyses under distinct load cases + knockdown factors to account for the unknowns.

Hypersonic vehicles: High aero-thermo-mechanical loads and environmentally-assisted damage induced by sustained exposure to extreme environments renders current design and sustainment practice ineffective.

Technical Challenges:

Gaining the capability to track damage mechanisms that occur at the microstructure level during structural simulation. –> Solution: Efficient, accurate multiscale methods.

Gaining the ability to account for the coupled thermal, mechanical and environmental degradation processes. –> Solution: Multiphysics failure models.

Multiscale-Multiphysics Computational Framework

The variational multiscale enrichment (VME) method is employed for elasto-viscoplastic materials and incorporate the microstructural damage mechanisms into the structural scale simulation.

Premise of the VME is accurate resolution and modeling of the microstructural response at critical subdomains (hotspots), in which damage is likely to occur. The response within the remainder of the problem domain is idealized based on phenomenological modeling.

Additive decomposition of the displacement field: