| Description |
In order to continue to improve understanding of the mechanisms which govern plastic deformation such as dislocation slip and twinning, new experimental techniques capable of resolving full-field displacement and strain maps at reduced length-scales are needed. The work outlined in this thesis is directed toward the transition of a macroscale experimental technique called the grid-method to the microscale so that it can be used in in situ scanning electron microscopy experiments. Challenges associated with transitioning the grid method technique from the macroscale to microscale are depositing required pattern in reduced length-scale, accounting for the noise and distortions inherent to the scanning electron microscope and integration of a setup for in situ testing. Each of these challenges was addressed and overcome. Pattern deposition was performed using a Focused Ion Beam, and complications such as image drift during deposition and achieving appropriate image quality were surmounted. The noise and raster-based image capture inherent to SEM imaging are equipment specific. New distortions that are induced by the raster scan were identified, and through judicious filter selection and implementation, observed distortions were significantly reduced without negatively affecting obtained deformation and strain field heterogeneities. A miniature vacuum-rated Psylotech load frame was integrated within a JOEL 5910 SEM and successfully used to study intra and intergrain deformation processes in an Aluminum 1100 specimen. Taken together, the efforts presented in this thesis have resulted in the development of a novel scanning electron microscope based grid-method technique, which leverages accepted approaches in experimental solid mechanics and image processing. The developed technique provides desired distortioncorrected full-field displacement and strains maps. Additionally, the technique is inherently length-scale independent, noncontact and material agnostic, thus it has promised to make broad impacts in the experimental mechanics community. |
