Endoscopy is a detection instrument that integrates traditional optics, human engineering, precision machinery, modern electronics, mathematics, and software[1]. Based on whether the shaft can change direction, endoscopes are classified into rigid scopes and flexible scopes. Snake bone is an important component of the flexible scope that enables bending, and its performance significantly impacts the quality of the endoscope. Snake bones include one-piece snake bones and multisegmented snake bones, and one-piece snake bones are simpler and more reliable than multi-segmented snake bones. In this paper, a three-dimensional model of a one-piece snake bone is designed, and the flexural performance of the snake bone is studied by finite element simulation. During the simulation, the material properties of the snake bone are defined, and the actual working state of the snake bone is simulated by applying load. The simulation results of different parameters of the snake bone were compared, and the key parameters of the snake bone structure were optimized.
AlON ceramic is widely used in the fabrication of high-quality infrared optical components, and has broad application prospects in aerospace, transparent armor, and infrared weapon windows. A laser can be applied to the processing of AlON ceramic in order to achieve a more flexible and efficient processing of AlON ceramic. In this paper, laser drilling experiments were carried out on AlON samples to investigate the mechanism of laser processing of AlON ceramic. A two-dimensional simulation model of laser ablation of AlON ceramic was established, and the process of material removal was analyzed. By comparing the experimental results with the theoretical analysis, the effect of defocus distance on the quality of AlON laser processing is analyzed.
Conformal window is a protective and imaging element in the optical system of high speed flying missile. Its surfaces are required to have the ultra-precision level of surface finish and profile accuracy to ensure good imaging quality and excellent aerodynamic. The large size and high steepness of conformal window bring great challenges to the high- precision manufacturing of inside and outside surfaces. In this paper, an ultra-precision grinding process was designed for conformal window with high steepness. The problems existing in the process of machining the inner and outer surfaces of the window were analyzed, and the most suitable grinding methods for the inner and outer surfaces were determined respectively. Furthermore, the ultra-precision grinding process of conformal window were designed and verified in detail. The research of this paper can be used as a guideline for ultra-precision manufacturing of large-size optical components with high steepness.
Polycrystalline aluminum elements with optical surface quality are widely used in optical fields, such as inertial confinement fusion (ICF) fusion target and optical reflection mirrors, etc. However, the surface height difference induced by elastic deformation after cutting strongly affect the surface quality of polycrystalline aluminum precision parts. In this paper, a crystal plasticity finite element (CPFE) model of the single point diamond cutting for bi-crystal aluminum material was firstly established through the software ABAQUS with the VUMAT subroutine. The surface height difference in diamond cutting of bi-crystal aluminum was investigated by the FE simulations. The surface height difference between grains after machining was extracted from the simulation results, and the suppression law of height difference caused by material properties and cutting parameters was investigated, which provides a theoretical basis for realizing high-quality surface control.
Diamond material has been widely used in the manufacture of high performance optical components due to its excellent mechanical and optical properties. CVD diamond can be used as inertial confinement fusion (ICF) target, X-ray lens of the fourth-generation light source, and infrared window, etc. In order to achieve high quality manufacturing of CVD diamond components, laser-induced graphitization technology can be used to improve the machinability of CVD diamond surface. In this paper, the surface generation mechanism of CVD diamond under laser irradiation were studied by molecular dynamics (MD) simulation. Firstly, a model of polycrystalline CVD diamond under laser ablation was established to reveal removal and evolution of surface materials at the atomic level. The MD simulation results with different grain sizes under laser irradiation were compared, and the influence of grain boundaries and grain size on laser graphitization was determined. Finally, the laser machining processes of CVD diamond were simulated under different laser spot diameters, and the influence of laser area on the graphitization degree of CVD diamond surface was analyzed.
BK7 optical glass is widely used as aerospace optical window. Precision grinding is a common method for machining BK7 optical elements. CVD diamond grinding wheel is a cutting tool with excellent wear resistance, which can realize high efficiency grinding for BK7. However, due to its small chip space, the surface quality will be affected by the large grinding force and difficult chip removal. In this paper, micro-grooves with different angles and widths were fabricated on CVD diamond grinding wheel surfaces by picosecond laser to improve the chip space. The grinding experiments of BK7 were carried out using these micro-structured wheels. The results show that the grinding force was reduced by 80% at most compared with the unstructured wheel, and the machined surface roughness was also decreased by up to 85%. The grinding force of structured CVD diamond grinding wheel decreases with the increase of the surface micro-structure groove angle. With the increase of groove width on the surface of structured CVD diamond grinding wheel, the surface roughness of the workpiece decreases first and then increases. When the groove width is 80μm, the surface roughness of the workpiece reaches the minimum value.
The micro-intersecting cylindrical mandrel is a kind of high precision optical micro-nano element in the inertial confinement fusion (ICF) experiment. It has a complex structure and high precision requirement, and its machining quality directly affects the accuracy of ICF experiment. In this paper, the ultra-precision milling technology of polycrystalline oxygen-free copper micro-intersecting cylindrical mandrel was carried out. The composition of the surface defects after cutting were determined, and the formation mechanisms of different defects were analyzed. The optimal ultra-precision milling process was designed. The surface roughness Ra value of the machined cylinder 1 is 16 nm, and the Rq value is 21 nm. The surface roughness Ra value of the machined cylinder 1 is 20 nm, and the Rq value is 24 nm. Besides, the boundary defect in the transition arc region was eliminated. Finally, the polycrystalline oxygen-free copper micro-intersecting cylinder part with high surface quality and near no defect was manufactured after ultra-precision milling.
A series of ultra-precision grinding experiments were carried out on transparent AlON ceramic. The grinding parameters (wheel speed, workpiece speed, feedrate and depth of grinding) were optimized by studying the influence of process parameters on surface quality. Comprehensive consideration of surface quality and machining efficiency, the grinding process parameters selected for finishing are as bellow: the wheel speed is 6000rpm, the workpiece speed is 39rpm, the feedrate is 5mm/min and the depth of grinding is 3μm. A grinding verification experiment was carried out after optimization. According to the optimized process parameters, the AlON optical window (the diameter is 120mm, the length-diameter ratio is 1.08, the thickness is 3mm) was processed by ultra-precision grinding. The form accuracy, surface roughness and infrared transmittance of the AlON optical window were tested and discussed.
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