Multi-scale Modeling in Novel Materials Design
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Authors
Ombogo, Jamie
Issue Date
2024
Type
Dissertation
Language
en_US
Keywords
Fatigue model , Fracture model , Martensitic phase transformation , Molcular dynamics simulations , Phase field simulations , Twinning dislocations
Alternative Title
Abstract
Advancements in the manufacturing industry drive the creation of innovative technological products, with materials design at its core. Understanding the physical processes dictating mechanical properties is crucial for accurate material design. Traditionally, this involved costly experimentation to test materials under various conditions such as static loading, fatigue loading, or thermal irradiation. On the other hand, modern multiscale modeling techniques offer a more efficient approach, reducing trial and error and enabling the design of material models that accurately describe complex behaviors. At the nanoscale, molecular dynamics (MD) simulations track atomistic microstructural evolution, often impossible to observe experimentally. Meanwhile, phase-field simulations at the meso-continuum scales mathematically model material behavior with a broader range of applications. For instance, MD simulations have elucidated monotonic loading and quenching mechanisms in magnesium (Mg) and titanium (Ti), delving into twinning nucleation and growth processes. While classical twinning theory typically relies on a dislocation-based approach, our recent simulation results indicate twinning can also arise from phase transformations. Depending on the material's phase diagram, specific types of twins, such as {101 ̅2} and {101 ̅1} twins, can form. Moreover, we explore defects in the lesser discussed ωphase, including twinning within this phase. At the meso-continuum scale, we discuss a framework for multiscale coupled phase field modeling of fracture and amorphization in boron carbide material systems. This framework investigates the unusual impact softening observed experimentally in this material, with practical implications for improving its application in bulletproof vests. We then extend the fracture part of this model to represent the cyclic fatigue process in Single Edge Notched Tension (SENT) and Compact Tension (CT) specimens, which are commonly used to investigate the fracture toughness of various materials.