About this talk
This talk will focus on work done in my group with emphasis on direct measurements of stresses during mesoscale microstructural deformation of Ni based and Zr based alloys during 3-point bending tests for fracture toughness at elevated temperatures. A novel nano-mechanical Raman spectroscopy measurement platform was designed for temperature, stress, and chemistry mapping at micro to nanoscale for different temperature and load conditions. During the 3-point bending test to measure fracture toughness of micron sized samples, notch tip plastic stresses as a function of microstructure, load, and temperature, with micron scale resolution were measured. The temperature field distribution was correlated to stress distribution and residual microstructure stresses around the area of the notch tip. The mechanical properties which include the elastic modulus, hardness and stress-strain relation at the plastic zone around the notch tip were also measured and compared before and after the bending tests. A new finite element method formulation that incorporated different elastic and plastic material properties from indentation experiments at different locations was validated using the experiments.