【作者】 杨宏伟；

【导师】 戴福隆；

【作者基本信息】 清华大学 ， 固体力学， 1995， 博士

【摘要】 本文提出并实现了超细网格法频域分析技术，从理论上推导了利用数字信号处理领域中的频域分析技术提取超细网格显微图象变形数据的处理过程，为发展细观实验研究的实时测量方法奠定了理论基础，同时也为在细观实验研究中继续利用相关学科的新技术成果建立了一种开放性的联系。 本文建立了超细网格法的数字图象处理系统，开发了显微网格图象的二维离散傅立叶变换和图象转置等计算过程的快速、高效的算法，并设计了以频域剪裁窗为特色的频域分析软件，实现了从显微网格图象中提取位移场、应变场等变形信息的全场快速自动处理，同时还可以灵活简便地实现位移场分离和网格倍频。 本文在包含微缺陷的材料微区内首次制备成功了零厚度超细网格栅，采用了旋转点光源高频栅制备技术和激光加工等微细加工技术，实现了对细观尺度微区变形信息的实时定量传感，而且不存在剪切滞后效应和增强效应等影响细观测量的不利因素。在各种温度环境中以及准静态和动态加载条件下都能对材料细观微结构的演变过程进行实时准确监测。 本文通过多种显微途径实现了对超细网格变形情况的实时观察和记录，并在扫描电镜观察和记录过程中避免了在试件表面蒸镀导电膜的环节，将扫描电镜从一种破坏性的微细观观察方法转化成了非破坏性的观察和记录方法，从而不仅观察和记录了特定微区内超细网格变形情况的显微图象，而且获得了反映细观尺度材料微结构演变过程的真实图象。 本文首次用超细网格法对包含微缺陷的铜箔试件的延性损伤演化和破坏过程进行了实验研究，观察和记录了损伤演化过程中的一些重要的细观实验现象，例如微孔洞的长大过程，微孔洞附近微区变形局部化现象，剪切带内的二级微孔洞及其演化等，并根据细观结构的变化分析了材料的失效过程。为细观损伤力学理论研究提供了重要的实验依据。本文首次对面积为0.01mm~2并包含微缺陷的微区变形分布进行了定量测量。 本文以上工作使光测力学的研究范围进入到了细观领域，无论对细观力学理论研究的深人发展，还是对新材料力学规律的探索和认识都具有重要的意义。更多还原

【Abstract】 Frequency domain analysis of deformed micro— grids is presented and realized in this paper. Frequency domain analysis, which is one of the most important techniques in modern signal processing field, is utilized to extract deformation data from the microscopic images of deformed micro-grids. The mathematical derivation of the extraction procedures in this paper founds the theoretical basis for the development of a real-time measurement method in the experimental researches of micromechanics. Furthermore, an opening interface is proposed to continue to take advantage of new technical achievements of interrelated subjects.An automated system of micro-grids using digital image processing and frequency domain analyzing techniques is established in this paper. By developing fast and efficient algorithms for two-dimensional discrete Fourier transform and matrix transposing of microscopic grid images, and by designing the frequency domain analysis software with a clip window in frequency domain, the deformation data are extracted from microscopic grid images automatically, whole— fieldly and with fast processing speed. Meanwhile, the separation of displacement fields and the multiplication of micro-grids have also been realized simply and conveniently.Zero—thickness micro-grids are successfully fabricated within a tiny area of the material surface which contains microscopic flaws. The technique of using a rotating point source to obtain high quality holographic gratings and some fine machining techniques such as lazer machine are utilized. The deformation informations in microscopic areas of the material are transmitted quantitatively in real-time and free from the unfavorable influences of shearing retardation effect and strengthening effect. The presented zero-thickness micro-grids make it possible to monitor the developing process of microscopic structures under quasi—static and dynamic loads and various temperature conditions.更多还原