Simulation of residual stress heterogeneities using cellular automaton

拟议的研究是先前的发现补助金的延续，该补助金致力于使用元胞自动机（CA）模拟钛合金的冷蠕变/疲劳相互作用行为。在本提案中，CA将用于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。这将有助于建立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，作为物理系统数学描述的另一种框架。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，它们尚未在材料科学和机械工程的框架中广泛使用。该建议的主要目的是开发能够估计表面处理过程引起的残余应力不均匀性的CA模型。次要目标将包括实验技术的发展，以验证所开发的模型和适应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。表面处理，如机加工，表面强化（锤击或喷丸），或感应淬火将进行研究。本建议也将包括实验验证。通过x射线衍射技术测量的残余应力分布提供了第一个验证参数。然而，对残余应力分布及其局部相关性进行精确的实验验证是一个很大的挑战。必须进行的测量尺度将要求开发出新颖而精确的技术。获得此类数据的方法之一是使用与魁北克水电研究所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组织的疲劳寿命预测模型中。

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.