Heterogeneous deformation of polycrystalline materials is established through mapping the strain fields on the surface of a Ni-based superalloy. This novel experimental set-up combines strain field mapping from digital image correlation (DIC) with microstructure information from electron backscatter diffraction (EBSD) during ex-situ loading. The results produce sub-micron spatial resolution of the strain fields on the surface of the specimen. Given the orientation information from EBSD, the strain can be decomposed into individual slip systems. Thereby allowing measurements of high-resolution strain heterogeneities at the interface with characterization of the interface structure, which is an excellent complement to the atomistic simulations of slip-GB interactions. This experimental technique provides means for verifying and validating modeling efforts.
We have advanced this technique via in situ DIC within a scanning electron microscope, which allows for higher resolution imaging. In fact, individual slip bands are visible, and the amount of strain accumulated within each band is quantified. Another advancement to the DIC technique, in collaboration with Andrew Cannon (1900 Engineering) and Jacob Hochhalter (NASA Langley) is a highly precise and repeatable micro-stamp to apply the speckle pattern necesary for DIC.
Project Sponsors: National Science Foundation, Rolls-Royce Corporation
Esquivel J, Sangid MD, “Digital image correlation of heterogeneous deformation in polycrystalline material with electron backscatter diffraction,” For presentation at Microscopy & Microanalysis 2015, Portland, OR, August 2-6, 2015. ID: 0546-000591.
Cannon AH, Hochhalter JD, Mello AW, Bomarito GF, Sangid MD, “MicroStamping for improved speckle patterns to enable digital image correlation,” For presentation at Microscopy & Microanalysis 2015, Portland, OR, August 2-6, 2015. ID: 0546-000769.
Abuzaid W, Sangid MD, Carroll J, Sehitoglu H, Lambros J, “Slip transfer and plastic strain accumulation across grain boundaries in Hastelloy X,” Journal of the Mechanics and Physics of Solids 60 1201-1220 (2012).
Abuzaid W, Sangid MD, Sehitoglu H, Carroll J, Lambros J, “The role of slip transmission on plastic strain accumulation across grain boundaries,” Procedia IUTAM, International Union of Theoretical and Applied Mechanics, University of Cachan, Paris, France, July 3-8, 2011.