AFRL-AFOSR-VA-TR-2016-0308 Hierarchically-Driven Approach for Quantifying Fatigue Crack Initiation and Short Crack Growth Behavior inAerospace Materials

Here, we present a hierarchical form of multiscale modeling to understand fundamental issues ofdeformation in Ti. This report presents our effort in the following areas,1. Effects of oxygen on prismatic faults in -Ti: A combined quantum mechanics/molecular mechanicsstudy2. Nano-indentation and slip transfer (critical in understanding crack initiation)3. An extended-finite element framework (XFEM) to study SCG mechanisms4. Atomistic methods to develop a grain and twin boundaries database in -Ti to quantify and developa. a crack initiation model,b. the necessary cohesive zone models for interfaces and single crystals, andc. a crystal plasticity modelFundamental to the development of a hierarchical atomistic-continuum methodology for SCG is thedevelopment of appropriate crack initiation models, cohesive zone properties, crystal plasticity models, andthe microstructure based finite element framework, i.e., in this case, we are using an XFEM. Overall, weDISTRIBUTION A: Distribution approved for public release. have generalized XFEM to include implicit representation of grains and grain boundaries. The newformulation can incorporate microstructure features directly based on EBSD data using level setformulations. Furthermore, an atomistic database of interactions of dislocation-impurities was developed.Using the developed database an appropriate crystal plasticity model was developed to investigate SCG inTi alloys.Distribution StatementThis is block 12 on the SF298 form. Distribution A Approved for Public ReleaseExplanation for Distribution StatementIf this is not approved for public release, please provide a short explanation. E.g., contains proprietary information. SF298 FormPlease attach your SF298 form. A blank SF298 can be found here. Please do not password protect or secure the PDFThe maximum file size for an SF298 is 50MB. SF298 FA9550-13-1-0144.pdfUpload the Report Document. File must be a PDF. Please do not password protect or secure the PDF . Themaximum file size for the Report Document is 50MB. FA9550-3-1-0144 Solanki Final.pdf Upload a Report Document, if any. The maximum file size for the Report Document is 50MB.Archival Publications (published) during reporting period: 1. Bhatia, M.A., Solanki, K.N. (2013). Energetics of vacancy segregation to symmetric tilt grain boundariesin HCP materials, Journal of Applied Physics, 114 (24), 244309.2. Bhatia, M.A., Zhang, X., Azarnoush, M., Lu, G., Solanki, K.N. (2015). Effects of oxygen on prismatic faultsin -Ti: A combined quantum mechanics/molecular mechanics study, Scripta Materialia, 98, 32-35.3. Bhatia, M.A., Azarnoush M., Adlakha I., Solanki, K.N.* (2016). Dislocation core structure and dynamics ofα-Ti: A molecular static and dynamic study, MSMSE, (minor revision).4. Bhatia, M. A., Solanki, K.N., (2016) Solute Effect on (10-12) Twin Boundary in Titanium: A first principlestudy, Materials Research Letters, (in review).5. Bhatia, M.A., Adlakha, I., Solanki, K.N.* (2016). Interactions between lattice dislocations and grainboundaries in α-Ti, Scripta Mat (in review).6. Solanki, K.N., Bhatia, M.A., Zhang, X., Azarnoush, M., Lu, G. (2015) Role of oxygen on mechanicalproperties of high temperature materials: A QM/MM study, the 2015 TMS annual meeting, Orlando, FL. 2. New discoveries, inventions, or patent disclosures:Do you have any discoveries, inventions, or patent disclosures to report for this period?