Analysis of the anisotropy influence on quasistatic and cyclic deformations of nickel base alloys by combining FEM methods with variational image processing

我们的项目旨在研究局部各向异性对多晶镍基合金的弹性和塑性行为以及初始疲劳损伤的影响，结合原位变形实验，创新的图像分析方法和有限元模拟。与其他金属材料相比，镍基合金的疲劳行为受到其固有的弹性各向异性的强烈影响，弹性各向异性强烈影响多晶显微组织中的应力和应变分布。在工程部分的实验和模拟之间的直接相关性将确保由镍基合金Inconel 617与厚度低于平均晶粒尺寸的板的原位测试。在标距部分的两个平坦侧通过SEM/EBSD进行表征，提供了局部准2D晶粒结构与通过变分流动和变形模型进行图像分析计算的应变分布的直接相关性。在数学部分，多模态SEM/EBSD图像从原位测试标本的变分模型将开发预处理数据，以及提供应变测量和损伤检测。通过变分模型计算的应变场将与具有相同初始晶粒形态的FEM模拟进行比较。这允许验证和优化FEM模型（如果需要）。在此基础上，验证的有限元模型被用于系统的参数研究不同形态的晶粒结构，以了解晶粒邻域效应以及不同的纹理的影响。对薄平板样品进行疲劳测试，并进行彻底的SEM分析，有助于将应变浓度和相关的晶粒形态与疲劳损伤过程联系起来。我们的跨学科研究将提供更深入的了解晶粒取向和弹性各向异性对镍基高温合金局部变形行为的影响，通过有限元法结合变分图像处理确定，以及局部变形与材料疲劳损伤的相关性。从申请人的观点来看，这允许从方法学和对所研究的材料类别的理解的观点来看，与实际的现有技术相比有实质性的进步。

Our project aims to investigate the influence of local anisotropies on the elastic and plastic behavior as well as initial fatigue damage in polycrystalline Ni-base alloys by combining in situ deformation experiments, innovative image analysis methods and FEM simulations. The fatigue behavior of Ni-base alloys is strongly influenced by their intrinsic, compared to other metallic materials exceptionally pronounced, elastic anisotropy, which strongly affects stress and strain distribution in the polycrystalline microstructure. Direct correlation between experiment and simulation in the engineering part will be assured by in situ testing of sheets made of the Ni-base alloy Inconel 617 with thicknesses below the average grain size. Characterization by SEM/EBSD at both flat sides of the gauge section provides direct correlation of the local, quasi 2D grain structure with the strain distributions computed by image analysis via variational flow and deformation models. In the mathematical part, variational models for multimodal SEM/EBSD images from in situ tested specimens will be developed for preprocessing the data as well as for providing strain measurements and damage detections. The strain fields computed by the variational model will be compared to FEM simulations with identical initial grain morphology. This allows verification and, if needed, optimization of the FEM models. Based on this, the validated FEM model is used for systematic parameter studies of grain structures with different morphologies to understand the influence of grain neighborhood effects as well as different textures. Fatigue tests at thin flat samples accompanied by thorough SEM analysis serve to correlate strain concentrations and associated grain morphologies with fatigue damage processes. Our interdisciplinary investigations will provide a deeper understanding of the influence of grain orientation and elastic anisotropy on the local deformation behavior of Ni-base superalloys, determined by FEM in conjunction with variational image processing, and the correlation of local deformation with the fatigue damage of the material. This allows, from the applicants’ point of view, substantial progress compared to the actual state-of-the-art, both, from the viewpoint of methodology and understanding of the investigated material class.