Effects of Heterogeneity, Anisotropy and Length Scale Effects in Microscale Deformation Processes

本研究的目标是系统地、单独地研究在微尺度制造中遇到的微尺度材料变形过程中的各向异性、非均质性和长度尺度效应的影响。虽然本研究中采用的技术可以应用于任何微尺度制造过程，但pi将重点研究微激光喷丸成形（mLPF）。该方法是通过使用微尺度x射线衍射技术测量诱导残余应力，通过电子背散射衍射（EBSD）测量塑性变形的分布和程度，以及使用各种商业技术测量变形样品的最终形状，来实验表征受mLSP和mLPF工艺影响的材料。为了分离各向异性的影响，这些过程将在单晶上进行。为了隔离非均质性的影响，该过程将在双晶的晶界附近进行。塑性变形的潜在长度尺度效应将用电子背散射衍射（EBSD）来探测，它可以估计几何上必要的位错的密度。这两个过程将使用有限元技术进行数值模拟，考虑到速率效应、硬化效应、各向异性、材料的非均质性，如果实验结果认为有必要，还将纳入长度尺度效应。预期的结果将有助于微制造工艺制造出更高质量的微元件。对工艺能力和限制的理解的显著提高将为新的微零件设计开辟机会。人才培养和成果传播将提高国家在微制造领域的竞争力。将作出重大努力，让传统上代表性不足的背景的学生参与研究。

The objectives of the proposed research are to systematically and individually study the effects of anisotropy, heterogeneity and length scale effects in microscale material deformation processes which are encountered in microscale manufacturing. While the techniques to be employed in this research could be applied to any microscale manufacturing process, the PIs will focus efforts Micro Laser Peen Forming (mLPF). The approach is to experimentally characterize materials subjected to mLSP and mLPF processes by measuring the induced residual stresses with microscale x-ray diffraction techniques, by measuring the distributions and degrees of plastic deformation with Electron Backscatter Diffraction (EBSD), and also to measure the final shape of the deformed specimens using various commercial techniques. In order to isolate the effects of anisotropy the processes will be performed on single crystals. To isolate the effects of heterogeneity, the processes will be performed near the grain boundary of a bicrystal. Potential length scale effects of the plastic deformation will be probed with electron backscatter diffraction (EBSD) which allows estimates of the density of geometrically necessary dislocations. The two processes will be numerically simulated using the finite element technique, taking into account rate effects, hardening effects, the anisotropic, heterogeneous nature of the material, and will incorporate length scale effects if deemed necessary by the experimental results.Expected results will help micro manufacturing processes to make higher quality micro components. The significantly improved understanding of process capability and limitations will open up opportunities for new micro part designs. Personnel development and dissemination of results will improve national competitiveness in micro manufacturing. A significant effort will be made to involve students from traditionally underrepresented backgrounds in the research.