Papers by Keyword: BK7 Glass

Abstract: Ballistic performance has been studied by impacting a long rod projectile into a bulk glass material and a layered specimen. The shock wave interaction on the material boundaries showed that it greatly influences the fracture configuration of glass material. A high speed photographic technique was applied in the experiment to observe the shock wave interaction and damage evolution in the bulk material. Transparent BK7 glass was used as the main material to observe the dynamic fracture phenomena. The depth of penetration (DOP) was measured to assess the ballistic efficiency of the bulk specimen compared with specimens that consisted of selected inter-layer materials, specifically rubber and a steel plate. The obtained results show that the use of a lower impedance material as an inter-layer is effective to enhance the ballistic performance while reducing the shock amplitude and delaying the wave propagation. These findings are in good agreement with the results of a numerical analysis using AUTODYN.

Abstract: The temperature and thermal stress distribution on BK7 glass was numerical simulated by MATLAB according to heat conduction theory. Research has shown that the laser pulse number, spot radius and pulse width can change the extent of the damage threshold for BK7 glass. The results shown the damage threshold decreased with the laser pulse number and radius increasing. The laser power also increased with the pulse width reducing. At the same time, the damage threshold was corresponding reduced.

Abstract: As the consumer market in the optics, electronics and aerospace industries grows, the demand of ultra-precision aspheric surface increases. The shape accuracy of the optical lens changes significantly with deformation conditions and optical properties of the lens varies with stress distribution within the lens. Therefore, determining the deflection and stress of glass lens is very important to improve the quality of the lens. In this paper, the deflection and stress theoretical results of BK7 glass plate have been presented in different cases of elastic deformation processing. The results are compared with the finite element analysis (FEA) to demonstrate the robustness and accuracy of algorithm in calculation of stress and deflection. The mentioned finite element models were established using the software Abaqus/CAE. The analytical and FEA results showed that if the edge of plate is simply supported, the maximum deflection is 4 times larger than in the fixed edge case. Otherwise if the edge and centre point of plate is simply supported, the maximum deflection is 2.5 times lower than in the fixed edge case and 11.3 times lower than in the simply supported at edge case.

Abstract: The confine of ductile-mode cutting and brittle-mode cutting seems to be a crucial step for designing a brittle material removal process. However, the existing transition from ductile-mode to brittle-mode for BK7 material makes the confine of different mode very difficult. Through a series of micro/nano-machining tests, measurements of cutting forces and morphological appearance of cutting groove as well as the cross section at the certain depth of cut, the confirmation of ductile-mode cutting, transition-mode cutting and brittle-mode cutting has been clearly described in the paper. This lays a foundation for the fundamental understanding of cutting physics concerning of material characteristics and cutting tools, and thereafter for the development of optimal process technology.