Multi-Scale Experimental and Computational Investigation of Microscale Origins of Ductile Failure

Metals are exposed to countless scenarios in service in which ductile fracture leads to early failure. This award supports fundamental research to understand the origins of this failure type in engineering metals. Using experiments, computational simulations, and data science approaches, the research aims to identify links between key features in the microstructure of metals and their propensity for failure under a wide range of real-world loading conditions. The research findings will enable the more efficient use of existing materials and the design of new materials with tailored microstructures for superior damage tolerance, energy absorption, or fracture performance. These features are key to enabling increased component safety, cost savings, and reduced environmental footprint. The award will provide education and training at undergraduate and graduate levels through student research and will build on an existing partnership with Clark Atlanta University through a faculty/student exchange program and hands-on workshops.The primary goal of this research is to quantitatively determine how multiaxial stress states, modified by local microstructure (grain misorientation and neighborhoods), promotes the development of dislocation structures that result in conditions directly preceding void nucleation in metals. While it is known that engineering measures of failure strain vary with stress state, how local microstructural features alter stress states resulting in fracture initiation is not well understood. The researchers will use experimental measurements (in situ scanning electron microscopy and synchrotron X-ray diffraction) and computational simulations (crystal plasticity and dislocation dynamics) analyzed through advanced regression methods to determine the relative importance and/or coupling of material, microstructural, and stress state features on ductility exhaustion of metals. By unraveling the intertwined roles of these effects, this research will enable the future development of novel fracture criteria that include explicit microstructural descriptions, facilitating the full use of current alloys and the development of superior materials.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.