Simulation of residual stress heterogeneities using cellular automaton

这项拟议的研究是之前发现基金的继续，该基金致力于使用元胞自动机(CA)模拟钛合金的冷蠕变/疲劳交互作用行为。在本方案中，将使用CA来研究制造材料在微观结构尺度上的残余应力分布和局部化。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、空间分布的动态系统，用作物理系统的数学描述的替代框架。除了提供计算优势外，CA还为数学分析提供了相关的框架，然而，它们在材料科学和机械工程的框架中还没有得到广泛的应用。该提案的主要目标是开发能够估计表面处理工艺引起的残余应力不均匀的CA模型。次要目标将包括开发实验技术以验证所开发的模型，以及调整基于微观结构的疲劳模型以考虑表面残余应力的统计方面。将研究表面处理，如机械加工、表面喷丸(锤击或喷丸)或感应淬火。本提案还将涵盖试验性验证。用X射线衍射法测量的残余应力分布提供了第一个验证参数。然而，残余应力分布及其局部相关性的精确实验验证是一个巨大的挑战。必须进行测量的规模将需要开发原创和精确的技术。获得这些数据的方法之一是使用与魁北克水电研究所共同开发的内部相关图像软件。最后，将CA模型收集的统计结果集成到各种基于微观结构的模型中进行疲劳寿命预测。

The proposed research is a continuation of a previous discovery grant which was dedicated to the simulation of the cold creep / fatigue interaction behavior of titanium alloys using Cellular automata (CA). In the present proposal, CA will be used to investigate the residual stress distribution and localization at the microstructural scale in manufactured material. This will help the development of statistical based models for fatigue life prediction of surface treated parts. CA which are fully discrete, spatial-distributed dynamical systems which serve as an alternative framework for mathematical descriptions of physical systems. In addition to providing computational advantages, CA also offer a relevant framework for mathematical analysis, however, they have not been extensively used in the framework of material science and mechanical engineering. The principal objective of the proposal is to developed CA models able to estimate the residual stress heterogeneities induced by surface treatment processes. Secondary objective will include the development of experimental technique to validate the developed models and the adaptation of microstructure based fatigue models to take into consideration the statistical aspect of surface residual stress. Surface treatment such as machining, surface peening (hammer or shot), or induction hardening will be investigated. Experimental validations will also be covered by the present proposal. The distribution of the residual stress as measurement by Xray diffraction techniques provides a first validation parameter. However, the precise experimental validations of the residual stress distributions and their local correlation represent a big challenge. The scale at which the measurements have to be done will require the development of original and precise techniques. One of the ways to achieve such data is the use of a in-house correlation image software developed with the research institute of Hydro Quebec. Finally, the statistical results gathered by the CA models will be integrated to various microstructural based model for fatigue life prediction.