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

在这项合作中，皮？S将开发一套基于图像的计算模型系统，用于有限变形晶体塑性建模，其中结合了真实材料微结构的形态特征和晶体取向。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，克服了传统有限元方法的局限性。多晶团聚体中的每个颗粒将由一个单一的超级元素表示，其中包含一个特殊的假定应力-塑性应变混合公式。该元素将具有自适应的分辨率增强功能，以表示微结构中不断演变的局部化区域和新生的裂纹。晶体位错密度也将被纳入空间场变量，这些变量可以对流和局部化，从而影响塑性硬化。将发展有效的多尺度格式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，用于模拟在疲劳裂纹模拟中捕捉萌生和演化所需的大量循环。将采用测量微结构对机械载荷的响应的新策略来校准本构模型。新的、不同规模的互补性实验将结合使用聚焦离子束(FIB)对试件的微加工以及在改进的纳米压头中进行测试和其他测试方法，从而能够提取高质量的单轴和简单弯曲本构数据，以及最先进的扫描电子显微镜和透射电子显微镜观察。界面将通过双晶体的支柱/悬臂测试以及取向显微镜(OM)分析、表面应变测绘和光学干涉测量相结合来表征。这些程序将构成开发对微观结构敏感的变形和损伤模型进行验证和确认所需的属性数据库的基础。该计划完成后，将对钛合金中微观结构对变形和失效特征的作用提供前所未有的详细和完整的理解。这对于可靠的材料设计是至关重要的，特别是在蠕变和疲劳特性方面。这一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节省将是巨大的，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.