Phase-Specific Analysis and Simulation of Micro Deformation and Damage in Metal Matrix Composites

应变的局部化和微观损伤在韧性材料如金属中的成核具有很高的技术意义，因为这些微观结构过程影响这些材料在加载、成形和加工期间的机械行为。此外，一侧的应变升高区域与另一侧的微观损伤位置和宏观破坏模式之间存在关系。为了控制这种微结构过程，例如通过分散硬颗粒来增强金属材料。本课题以Co/WC金刚石复合材料为例，采用二维/三维实验分析和数值模拟相结合的方法，在考虑残余应力的条件下，对金属基复合材料微观结构区域的微观变形和损伤过程进行了研究。由各种Co/WC金刚石金属基复合材料制成的试样将在拉伸中加载到不同的应变阶段。在这些阶段中，通过SEM和3D显微断层扫描（µCT）对样本的量规部分进行成像。将使用项目中建造的专用于µCT设置的试验台进行原位拉伸试验。将开发用于三维应变场的相特异性分析的相关算法，并将其应用于三维图像。该迭代相关算法考虑了可以从断层图像中提取的微结构中的相的分布。在此基础上，建立了Co/WC金刚石复合材料的三维有限元模型，模拟了复合材料的微观变形和损伤过程。在模型边界处测量的位移矢量场将用作FE模拟的边界条件。将模拟结果与基于应变场、残余应力和损伤过程的实验结果进行比较，将有助于验证模拟模型。有了这样一个经过验证的数值模型，它将有可能得到一个更好的理解的变形和损伤行为的复合材料进行参数研究有关不同的相排列和不同的相体积分数。实验分析和模拟之间的密切合作被认为是实现这些目标的关键因素。

The localization of strain and the nucleation of micro damages in ductile materials like metals are of high technical significance since these microstructural processes affect the mechanical behavior during loading, forming and machining of such materials. Moreover, there is a relationship between the regions of elevated strain on one side and the sites of micro damages and the modes of macroscopic failure on the other side. In order to control such microstructural processes, metallic materials are reinforced for example by dispersing hard particles. Such metal matrix composites (MMCs) have become more and more attractive since their mechanical properties can be tailored to various applications over a wide range.Using a combination of 2D/3D experimental analysis and simulation techniques and under consideration of residual stresses, this project aims at the understanding of micro deformation and damage processes in microstructural regions of MMCs by the example of the system Co/WC diamond:Specimens made of various Co/WC diamond MMCs will be loaded in tension to different stages of strain. In these stages, the gauge sections of the specimens are imaged by SEM and 3D micro-tomography (µCT). With a test rig which will be constructed in the project and which is dedicated for the µCT setup in situ tensile tests will be carried out. A correlation algorithm for the phase-specific analyses of the 3D strain fields will be developed and applied to the 3D images. This iterative correlation algorithm takes into account the distributions of the phases in the microstructure which can be extracted from the tomographic images. Furthermore, the effect of residual stresses, microstructural parameters and the Co/diamond bonding on the initiation of strain and stress concentration sites and the beginning of damage at a microscopic scale will be investigated.Based on the experimentally obtained phase distributions a realistic 3D FE model of the phase geometry of the Co/WC diamond MMC will be built up to simulate the micro deformation and damage processes of the investigated MMC. Displacement vector fields measured at the model boundaries will be used as boundary conditions for the FE simulation. The comparison of the simulation results with the experimental findings on the basis of strain fields, residual stresses and damage processes will help to verify the simulation model. With such a verified numerical model, it will be possible to derive a better understanding of the deformation and damage behavior of the composite by performing parameter studies concerning different phase arrangements and different phase volume fractions. The close cooperation between the experimental analyses and simulations is considered to be a key element for achieving these aims.