Optimizing Functionally Graded Materials to Resist Failure under Dynamic Loadings

摘要

After three years of the project, many of the proposed research topics have been completed and manuscripts were submitted for publication. First, for the dynamic crack propagation within functionally graded materials (FGMs), a novel fracture criterion was introduced. It is based on energy concept and controls crack growth rate and associated plastic dissipation flow. This model was implemented in dynamic failure analysis to investigate crack propagation within elastic plastic graded materials. The new procedure was also implemented for the impact of graded protective layer. The results confirmed the importance of modeling of cracking, revealed the effects of compositional gradation through-thickness. In a subsequent analysis, a procedure that utilizes an inverse analysis was developed to measure key fracture parameters. These parameters are difficult to measure with conventional means. Third, in collaboration with materials science group, material parameters of actual FGM were measured using the indentation and inverse method. The specimens were thermal barrier coatings fabricated with zirconia and NiCrAlY. This type of advanced scheme to post-process experimental data is essential for obtaining properties of complex systems. In addition, preliminary fracture tests were conducted for thicker FGMs to determine its fracture behavior.