SUBJECT: Ph.D. Proposal Presentation
BY: Hyung Nun Kim
TIME: Friday, May 17, 2019, 2:00 p.m.
PLACE: Love Building, 210
TITLE: Extracting effective local mechanical properties from heterogeneous materials using spherical-indentation stress-strain protocols: applications to polymer matrix composites and nickel superalloys
COMMITTEE: Dr. Surya R. Kalidindi, Chair (ME)
Dr. Richard W. Neu (ME)
Dr. Hamid Garmestani (MSE)
Dr. David L. McDowell (ME)
Dr. Mario P. Bochiechio (Pratt &Whitney)


Current methodologies for mechanical characterization of advanced heterogeneous materials poses a significant challenge due to difficulties in fabricating standard test specimen with representative microstructures of the intended manufactured part. These difficulties arise from microstructure sensitivity to any changes and optimization in the fabrication method for accommodating different part geometries. It follows that the mechanical properties collected from the standard test specimen may not represent well the true properties of the intended manufactured part. Additionally, in the event where fabrication of macro-scale standard test specimen is not feasible, micro-scale testing can be considered as an alternative. However, the complications involving micro-machining of small-scale test coupon to specified size and geometry incurs high demands on expertise, resources, and time; thus, only a limited number of measurements is practical.

To bridge this gap between materials development and manufacture, spherical indentation stress-strain protocols will be employed to extract mechanical properties of the as-manufactured part. To demonstrate the versatility of spherical indentation stress-strain protocols, the proposed work will present two case studies on fundamentally different material systems: a polymer matrix composite (PMC) system for hip implant applications, and a polycrystalline nickel superalloy gamma-gamma prime system for gas-turbine applications.

In the first case study, spherical indentation will be employed to collect effective mechanical properties of the as-manufactured PMC acetabular socket used in hip implants. In the second case study, spherical indentation will be employed to collect effective mechanical properties of individual grains containing gamma matrix and gamma prime precipitates in polycrystalline IN100 nickel superalloy. Furthermore, the indentation properties will be used to extract intrinsic grain properties, i.e., the elastic constants and critical resolved shear stresses. The proposed study will demonstrate the broad applicability of spherical indentation to collect mechanical properties from heterogeneous material systems where standard test method approaches are not well-suited for mechanical characterization.