复合材料细观全场三维变形的实验分析方法研究

In this project, a volumetric image processing method is proposed for acquiring the three-dimensional deformation of each element in a composite, based on the image sequence acquired by synchrotron radiation CT during the deformation of the material. First, the location and three-dimensional (3D) shape of each reinforcing element (e.g. individual fiber or particle) are automatically extracted by using image segmentation. Feature point matching and subimage matching are utilized to establish the correspondences between the extracted elements obtained before and after deformation. 3D shape registration is used to derive the displacement and the deformation from a pair of matched elements. The morphological feature points on the matrix contour are matched, and then incorporated with the deformation of the reinforcing elements to constitute the displacement boundary conditions of the matrix. The full-field deformation of the matrix is computed accordingly. The proposed method adds a new function to synchrotron radiation CT, which enables the measurement of the deformation distribution of each element in a composite. The enhanced experimental method is very important to the study of the relationship between the macroscopic mechanical properties and the micromechanical behaviors of a composite, as well as the optimization of the design and the manufacturing of composites.

本项目针对同步辐射CT测试复合材料所获得的体图像序列，提出一种体图像分析方法，能够获取材料内部全场及各组分自身的三维变形。首先通过体图像分割自动提取出各增强相（如纤维或颗粒）的空间位置和三维形状，运用特征点匹配和子图像匹配建立变形前、后增强相的对应关系，对匹配的增强相进行三维形状配准获取其位移和变形，然后对变形前、后的基体轮廓进行形状特征点匹配，再结合增强相的变形建立基体的位移边界条件，计算基体的全场三维变形。该体图像分析方法为同步辐射CT测试技术增添了材料内部各组分全场变形的分析方法，为研究复合材料宏观力学性能与细观力学行为之间的关系，以及优化材料设计和制备工艺提供了有效的实验方法。

本项目的主要研究内容包括以下几个方面：研究了基于B样条插值和预滤波的体图像相关方法，该方法能够有效地减少体图像中高频分量和亚像素插值导致的测量误差，并且有着较高的运算效率。基于三维数字图像相关方法分析了裂纹尖端三维变形场，研究了非均匀材料中不同区域的裂纹端部场在裂纹扩展过程中的变化规律。针对非协调接触问题，研究了基于局部位移场以及接触模型的接触力识别方法，可以用于测量接触面的分布力。建立了双分辨率的数字图像相关系统，并基于该系统分析了接触中的全场变形测试、应变集中分析等关键问题。该项目对于工程中广泛存在的接触现象以及断裂问题提供了基于光学方法的实验研究手段，具有一定的科研以及实用价值。