Conformal Sensor Window

Conformal sensor windows offer advantages over axisymmetric surfaces in the ability to reduce drag and weight. Materials of interest include spinel, polycrystal alumina, and ALON. However, the description, fabrication and metrology of these surfaces can be costly, or even impossible. Fabrication of these surfaces is difficult, since they are not axisymmetric and can have varying local radii of curvature, rendering grinding, lapping and polishing of these surfaces untenable. A method to overcome these difficulties in fabrication is to apply ductile mode machining (DMM) to eliminate grinding, lapping and polishing. DMM has been successfully applied to SiC mirror and Infrasil 302 glass transmission surfaces to achieve the requisite surface finish and figure error for axis-symmetric optics. Through the use of physics-based modeling, DMM conditions can be identified where material removal results in ductile chip formation, damage free surfaces and excellent surface finish. This SBIR activity extends the technology of DMM to torroidal configurations enabled by physics-based modeling technology. We will further develop and enhance its modeling capability for application to spinel workpieces. In Phase I we will demonstrate the feasibility of DMM to machine a spinel torroidal window in a laboratory environment with Breault performing the requisite metrology.