Deep-sea optical windows must withstand extreme hydrostatic pressure while maintaining optical transmittance, requiring a balance between mechanical rigidity and optical performance. Increasing thickness enhances structural strength but reduces transmittance. This study proposes a design method for deep-sea optical windows using domestically developed sapphire. Three-point bending tests were conducted on sapphire and silicon specimens, and B-criterion strength was derived using Weibull distribution to account for brittle material properties. Optical transmittance measurements established key design characteristics. Using theoretical formulations for rectangular planar optical windows under uniform external pressure, the initial design was based on experimentally derived sapphire properties. Finite element analysis of the optical window assembly confirmed sufficient structural stability margins above critical thresholds. Linear interpolation was applied to evaluate the continuous design space across discrete thickness values. A compromise solution was identified that satisfies both structural rigidity and transmittance objectives. By integrating experimental material characterization with numerical analysis, this study provides an effective framework for determining the optimal thickness of deep-sea optical windows and confirms the applicability of domestically developed sapphire as a reliable optical window material for high-pressure underwater environments.
This study experimentally investigates the laser-assisted diamond turning of high-hardness sapphire to enhance its precision machinability for defense optical components. Sapphire is an attractive material for applications such as transparent armor, sensor windows, and optical apertures due to its excellent mechanical strength, thermal and wear resistance, and outstanding optical transparency. In this research, precision cutting tests were performed on a diamond turning machine, and the resulting surfaces were characterized using a white-light interferometric profilometer. At an optimal laser power of 5 W, the surface roughness and form accuracy improved to 28.8 nm Ra and 191 nm RMS, respectively, demonstrating that laser assistance can significantly enhance surface quality. Microscopic observations after processing revealed a noticeable reduction in tool wear under laser-assisted conditions, which is likely to improve process stability and extend tool life. However, both insufficient and excessive laser power resulted in degraded surface quality compared to conventional turning, underscoring the importance of optimizing laser power. These findings highlight the potential for process optimization in laser-assisted diamond turning to improve the precision and reliability of sapphire machining, contributing to the future development of advanced manufacturing technologies for high-precision defense components.
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