Integrated Experimental- Computational Modeling of Deformation and Fatigue in Advanced Structural Materials

在这一合作努力中，PI？s将开发一个基于三维图像的有限变形晶体塑性建模计算模型系统，该系统结合了真实材料微观结构的形态特征和晶体学取向。一种创新的基于颗粒的自适应有限元模型将被创建，用于准确和高效的分析，克服传统有限元方法的局限性。多晶骨料中的每个颗粒将由一个包含特殊混合假设应力-塑性应变公式的单一超级元素表示。该元件将具有自适应增强的分辨率，以表示微观结构中不断发展的局部化区域和新生裂纹。晶体位错密度也将作为空间场变量，可以对流和局部化来影响塑性硬化。将开发有效的多标度方案来耦合位错密度模型和有效的粗晶塑性模型。GAFEM的发展还将伴随着一个多时间尺度模型，用于模拟大量的循环，以捕获疲劳裂纹模拟中的起始和演化。测量微观结构对机械载荷的响应的新策略将被纳入校准本构模型。在不同尺度上进行新颖的、互补的实验，将使用聚焦离子束（FIB）微加工测试物品，结合在改进的纳米压痕器和其他测试方法进行测试，从而提取高质量的单轴和简单的弯曲本构数据，以及最先进的扫描电镜和透射电镜观察结果。界面将通过双晶体的柱/悬臂测试以及取向显微镜（OM）分析、表面应变映射和光学干涉测量相结合来表征。这些程序将成为开发对微观结构敏感的变形和损伤模型进行核查和确认所必需的属性数据库的基础。该项目完成后，将为微观结构对钛合金变形和失效特征的作用提供前所未有的详细和综合的理解。这对可靠的材料设计至关重要，特别是在蠕变和疲劳特性方面。这种新模式的成功将引起GE航空等行业的极大兴趣，因为在安全关键应用中插入先进合金的时间和成本将大大节省，并将使行业超越现有技术。

In this collaborative effort, the PI?s will develop a system of 3D image-based computational models for finite deformation crystal plasticity modeling that incorporates morphological features and crystallographic orientations of real material microstructures. An innovative grain-based adaptive finite element model will be created for accurate and efficient analyses, overcoming limitations of conventional FE methods. Each grain in a polycrystalline aggregate will be represented by a single super-element incorporating a special hybrid assumed stress-plastic strain formulation. The element will feature adaptive augmentation of resolution to represent evolving localization zones and nascent cracks in the microstructure. Crystallographic dislocation densities will also be incorporated as spatial field variables, which can convect and localize to affect plastic hardening. Effective multi-scaling schemes for coupling the dislocation density model with efficient coarse-grained crystal plasticity models will be developed. The GAFEM developments will also be accompanied by a multiple time scale model for simulating large number of cycles required to capture initiation and evolution in fatigue crack simulations. New strategies for the measurement of microstructural response to mechanical loading will be incorporated for calibrating constitutive models. Novel, complementary experiments at different scales, will use a combination of focused ion beam (FIB) micromachining of test articles coupled with testing in a modified nanoindentor and other testing methods, enabling extraction of high quality uniaxial and simple bending constitutive data, and state-of-the-art SEM and TEM observations. Interfaces will be characterized with pillar/cantilever testing of bicrystals and with a combination of orientation microscopy (OM) analysis, surface strain mapping and optical interferometry. These procedures will form a basis for the development of property databases necessary for verification and validation of microstructure-sensitive deformation and damage modeling. The program, upon completion, will provide an unprecedented detailed and integrated understanding of the role of microstructure on deformation and failure characteristics in Ti alloys. This is critical to reliable materials design, especially with respect to creep and fatigue characteristics. Success of this new paradigm will be of great interest to industries such as GE Aviation since the time and cost saving for inserting advanced alloys in safety-critical applications will be tremendous and will allow industry to leapfrog present technologies.