Multi-scale Physics-Based Models for High Strength Titanium Alloys Accounting for Higher-Order Microstructure Statistics.

The goal of this proposal is to demonstrate the feasibility of new multi-scale models for linking higher order micro-structure descriptions to failure initiation and crack propagation for high cycle fatigue of high strength titanium alloys. This includes new high temperature materials such as the lightweight intermetallic titanium aluminide turbine blades to be used in the lower pressure sections of the Boeing 787 engine. The unified fracture initiation and propagation modeling will be incorporated into new software tools and integrated into a larger protocol for aerospace applications. Global Engineering Materials has established the business partnership with SIMULIA (ABAQUS) and will team with Prof. Lipton at Louisianan State University (LSU) to implement its standalone software package in customized Abaqus solution modules. The multi-faceted feasibility study consists of developing an add-on ABAQUS toolkit that will enable the following: 1) a new unified multi-scale fatigue crack growth modeling technique that incorporates micro-structural information obtained from Orientation imaging maps of polycrystalline alloys; 2) a novel multi-scale free energy based method for modeling crack/damage nucleation and evolution that is independent of the finite element mesh; 3) demonstration of the applicability and computational efficiency of the developed toolkit at the component and structural level. BENEFIT: The results from this research will have significant benefits and commercial application in the, DoD labs, and engine industries. It will result in: 1) a commercially viable, accurate, computationally efficient, and user-friendly virtual testing tool to simulate material and fracture properties for a given microstructure of titanium alloy; 2) an integrated analysis framework for fatigue damage prognosis and health management of engine components; 3) a virtual testing tool to reduce current certification and qualification costs which are heavily driven by experimental testing under various alloy configurations and stress; and 4) innovative damage tolerance design and risk management procedures to minimize the risk of fatigue damage. The tool can be used by government agencies and private industries as follows: 1) for material fabricators to accelerate innovative alloy design and material tailoring for a given design objective; 2) for research institutions and design agencies to explore the micro structural dependent crack initiation, corrosion fatigue, and abnormal small fatigue crack growth, 3) for structural certification and government agencies to specify fatigue performance limits and safety standards; and 3) for aircraft and engine manufacturers to provide optimal designs via the effective use of new analysis tools, risk evaluation methods, and health management procedures.