Ultra-precision machines utilize single crystal diamond tools to manufacture lenses (optics) with dimensional accuracy that is on the order of a small fraction of the diameter of a human hair (approximately one ten-millionth of one meter). New ultra-precision machine technology enables the manufacture of lenses (optics) of nearly arbitrary shape: freeform optics. This freedom allows lens designers to think in entirely new ways. As one of the enabling technologies for freeform optics, ultra-precision machining is poised to play a major role in an optical revolution. A prime application area of this technology is the manufacture of lenses for thermal imaging and surveillance, thermal imaging and night vision systems (infrared imaging). This award supports fundamental research needed for the cost effective manufacture of freeform infrared (thermal) optics. While the immediate impact area is infrared imaging, the research has broader application to many industry sectors critical to the U.S. economy including solar energy, healthcare, biomedical, aerospace, and automotive. This research crosses the disciplines of manufacturing, mechanical engineering, materials science and optical science. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.
Reports in the literature give numerous anecdotal examples of brittle materials that are machinable by diamond milling ("diamond millable") but are not generally considered "diamond turnable". The difference may be due to the interrupted or non-steady state nature of the cutting process. The objective of this research is to test the hypothesis that when diamond milling brittle materials, the characteristics of the surface and subsurface depends not only on the geometric parameters as in diamond turning, but also on the dynamic non-steady-state parameters such as the time-in-cut and the dynamically changing chip thickness. Researchers from UNC Charlotte and Oklahoma State University will design and construct a simplified milling experiment with the capability to isolate and measure the response of materials in different geometries ranging from those typical to milling to high-speed nano-indentation. The surface and subsurface characteristics will be measured with techniques ranging from atomic force microscopy to Rutherford Backscattering Spectrometry. The effort will target infrared (IR) optics manufactured in single crystal germanium and IR-transparent glass. Research results will not only enable more productive machining of the targeted materials, but also provide a scientific basis for expanding the range of "diamond millable" brittle materials for optical and other applications.
