Reliability-based topology optimization (RBTO) is used to obtain an optimal topology satisfying given constraints, as well as to consider uncertainties in design variables. In this study, RBTO was applied to obtain an optimal topology for the inner reinforcement of a vehicle's hood based on bidirectional evolutionary structural optimization (BESO). A multi-objective topology optimization technique was implemented to obtain the optimal topology for two models with different curvatures while simultaneously considering the static stiffness of bending, torsion, and natural frequency. A performance measure approach (PMA) with probabilistic constraints formulated in terms of the reliability index was employed to evaluate the probabilistic constraints. The optimal topology obtained by RBTO was evaluated and compared to that obtained by deterministic topology optimization (DTO). A more suitable topology was obtained through RBTO than DTO even though the final volume obtained by RBTO was generally slightly greater than that obtained by DTO. The multiobjective optimization technique based on BESO can be applied very effectively with topology optimization for a vehicle's hood reinforcement.
Photonic patterns were fabricated in fused silica, BK7, and Ge -doped borophosphosilica glass ( Ge -BPSG) using a focused femtosecond (fs)-laser beam. By focusing tens to hundreds of μJ fs-laser beam with a 10x microscope objective, we inscribed the semi-circular cavity patterns on the fused silica and the BK7. The inscribed hole diameters are 28 μm (fused silica) and 11 μm (BK7) at an input fluence of 71 J/cm2. This circular-cavity patterning is ascribed to the ablation via the multi-photon absorption process. For the application to functional devices, the surface relief gratings (SRGs) were made in fused silica and BK7 by focusing the fs-laser beam on the glass surface with a cylindrical lens and by translating the sample in the direction perpendicular to the focus line. The first-order diffraction efficiencies of the prepared SRGs are 34% (fused silica) and 14% (BK7). A refractive-index grating was also fabricated in the Ge -BPSG by using the two-beam interference method. The maximum index modulation of 2.5 × 10-3was obtained for 20,000 laser shots of 73 mJ/cm2per pulse. It is thought that the index modification occurs through the defect formation by the fs-laser irradiation.
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