A Computational Framework for Simulating Crack Nucleation and Growth in Materials Subjected to Dynamic Loads

Abstract

Understanding dynamic fracture behavior is essential for predicting the structural integrity and lifespan of engineering components, especially in critical fields like aerospace, civil engineering, and materials manufacturing. Dynamic fracture involves crack propagation under rapid loading conditions, where the loading rate impacts the fracture process.Dynamic fracture is particularly important in scenarios such as impacts, fragmentation, and high-speed machinery operations, where materials are subjected to sudden and extreme forces. Both crack nucleation and propagation are crucial in dynamic fracture. The precise conditions under which cracks nucleate is the key to predict failure onset and implementing preventive measures. Once a crack has nucleated, its propagation under dynamic loading is also challenging due to complex stress wave interactions and inertia effects that influence the crack path and speed. Traditional fracture analysis methods often struggle to accurately predict crack behavior under these dynamic conditions.The research presented in this dissertation aims to address the aforementioned challenges. A unified computational framework is developed to simulate both crack nucleation and growth under dynamic loads. In essence, a phase field model designed for fracture under quasi-static loading conditions is extended to account for dynamic fracture. The framework accounts for an arbitrary material strength surface through an external driving force in the evolution equation for the phase field. The framework is appealing because it models arbitrary material strength without sacrificing Griffith’s criterion. Additionally, it does not require splitting the strain energy density into “tensile” and “compressive” components. The developed computational framework has been validated against a broad range of experimental observations, demonstrating the importance of accurately representing material strength. A complete analysis of fracture nucleation and propagation during the Brazilian test is presented; the framework also simulates coupled acoustics, elastodynamics, and damage with application to nano-pulse lithotripsy; and the framework has been validated against the impact experiments by Kalthoff and Winkler [43], a dynamic version of the Brazilian fracture test [91], and a recent experiment investigating crack initiation, propagation, and branching in soda-lime glass specimens [10].