Elasto-plastic phase-field analysis of thermal induced-cracking and its application towards metal additive manufacturing

Metal Additive Manufacturing (MAM) technology has evolved significantly, transitioning from its initial role in rapid prototyping to becoming a pivotal component in manufacturing industries. Renowned for its versatility in product design, tooling, and process planning, MAM production systems face the challenge of understanding the intricate interplay of processing parameters and detecting solidification defects, such as hot cracking and porosities. To address this challenge, we propose a thermomechanical phase-field fracture model for predicting in-situ hot cracking, grounded in thermodynamic consistency. The computational simulation of such a complex process is challenging due to the interactive underlying physics and varying computational scales. To tackle this, we have developed a hierarchical multi-application framework. Initially, the framework activates elements with an adaptive mesh refinement (AMR) strategy to calculate the shape of cladding lines by the laser. Subsequently, another application captures thermal simulation information to calculate thermal strains in 3D shapes while considering cladding geometries. A third application focuses on phase-field fracture to assess the effect of thermal gradient and shrinkage strains in manifesting hot cracking. Considerations extend to shrinkage, thermal strain, and the rapid cooling stage in solidification crack evolution. Staggered time schemes are employed to control time variations between different applications, avoiding the loss of capturing crucial phenomena. Within the model, damage is intricately coupled with thermoelastic plasticity, incorporating informed heat conduction with damage parameters, and temperature-dependent fracture properties. Implemented through the finite element method within the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework, the coupled system of equations scrutinizes the influence of manufacturing process parameters, particularly the effects of laser power and scanning speed, alongside fracture properties. Comparative evaluations with experimental observations illuminate the evolution of thermal-induced cracking during the heating process. This comprehensive exploration aims to advance our understanding of the intricate dynamics governing MAM processes, contributing valuable insights to enhance manufacturing outcomes. Simulation results uncover key features of hot crack formation, shedding light on the fundamental understanding of crack formation mechanisms and process optimization.