Simulating nucleation and short crack propagation using cellular automaton in gradient microstructures

拟议的研究是以前的发现赠款的延续，致力于发展应用于微观力学的元胞自动机（CA）方法。由于这种支持，CA已被用于模拟冷蠕变/疲劳交互作用在钛合金和局部应力分布在多晶体的微观结构尺度。在本建议中，CA将进一步发展，以研究裂纹萌生和扩展的材料，包括微观结构梯度。这将有助于开发基于统计的表面处理零件疲劳寿命预测模型。CA是完全离散的、空间分布的动力系统，它是物理系统数学描述和分析的一种替代框架。尽管具有计算优势，但CA尚未在材料科学和机械工程框架中得到广泛应用，而目前的候选人是该领域的领导者。该提案的主要和长期目标是开发CA模型，该模型能够从表面处理过程和施加的载荷引起的应力和应变不均匀性计算裂纹的萌生和扩展，从而可以开发统计方法。次要目标包括进一步开发实验技术，以校准和验证开发的模型，记录在疲劳试验过程中的各种微观结构和合金的微观结构的适应。将研究表面处理，如机加工，表面喷丸（锤击或喷丸），渗碳或感应淬火，因为它们是候选人研究的一些表面处理。本提案还将涵盖实验验证。测量的规模要求开发原始和精确的技术，这些技术现在可用于进一步的材料调查。元胞自动机模型收集的统计结果将被集成到各种基于微观结构的疲劳寿命预测模型中。

The proposed research is a continuation of previous discovery grants dedicated to the development of Cellular Automata (CA) methods applied to micromechanics. Thanks to this support, CA have been used to simulate cold creep / fatigue interactions in titanium alloys and localise stress distributions at the microstructural scale in polycrystals. In the present proposal, CA will be further develop to investigate crack initiation and propagation in material including microstructure gradients. This will help developing statistical based models for the fatigue life prediction of surface treated parts. CA, which are fully discrete, spatial-distributed, dynamical systems, serve as an alternative framework for mathematical descriptions and analysis of physical systems. Despite providing computational advantages, CA have not been extensively used in the framework of material science and mechanical engineering and the present candidate is a leader in this domain. The principal and long-term objective of the proposal is to developed CA models able to calculate the crack initiation and propagation from the stress and strain heterogeneities induced by surface treatment processes and applied loads, allowing the development of a statistical approach. Secondary objectives include further development of experimental techniques to calibrate and validate the developed models by documenting the adaptation of the microstructures during fatigue tests for various microstructures and alloys. Surface treatment such as machining, surface peening (hammer or shot), carburizing or induction hardening will be investigated as they are some of the surface treatments investigated by the candidate. Experimental validations will also be covered by the present proposal. The scale at which the measurements have required the development of original and precise techniques that are now available for further material investigation. The statistical results gathered by the CA models will be integrated to various microstructural-based model for fatigue life prediction.