GOALI: Deformation and Cracking Behavior of Oxide Glass under Indentation

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NON-TECHNICAL DESCRIPTION: Crack-resistant glass is of paramount importance for a wide range of applications such as personal electronics, automobiles, solar panels, buildings, and submarine communications cables. This project aims to advance fundamental knowledge on crack initiation in glass under impact (e.g., dropping a smart phone with cover glass onto a solid floor). This project gains this knowledge by integrating in-situ experiments with virtual mechanical tests in large-scale computer simulations. An integrated education component is to develop computational modules for a required undergraduate course “Computational Materials Design”. Students involved in the project have opportunities to interact with researchers at Corning Incorporated in characterizing the structure of glasses and solving practical problems in the industrial setting. In carrying out this project, graduate and undergraduate students are trained in frontier areas of glass science and technology. On-going efforts are being made to inspire and encourage K-12 students to pursue science and engineering as a career path, by igniting curiosity in young minds and instilling confidence in women and underrepresented minorities.TECHNICAL DETAILS: Despite extensive studies, what controls crack initiation in glass under sharp contact loading remains elusive. The difficulty arises mainly due to the experimental complexity associated with in-situ investigations at a local scale (tens of microns) under complex and non-uniform stresses. In this project multiple in-situ optical diagnosis techniques such as Raman, optical microscopy and Brillouin light scattering are used simultaneously to characterize the evolution of structure and properties of glass under uniform stress states (e.g., hydrostatic, uniaxial compression or a mixed state) in a diamond anvil cell to provide the reference data necessary for understanding the glass response to sharp contact loading. Micro-Brillouin spectroscopy is used to map the residual densification underneath an indent and the residual stress field around an indentation with a spatial resolution of ~1 um. These results provide key insights in understanding the deformation and cracking behaviors of glass under indentation, and critical data for fitting potential parameters for molecular dynamics simulations of multi-component glasses and for validating computer models. Based on these reliable potentials, virtual mechanical tests such as 3D nanoindentation in molecular dynamics simulations with well-controlled parameters are carried out to provide a detailed understanding of the dynamic structural changes, the deformation modes, and the critical stress states that lead to the initiation of different types of cracks under indentation. Simulated 3D nanoindentation tests are providing the key missing information in experiments that has limited one’s understanding of how glass cracks.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.