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Scaling effects on the optical properties of patterned nano-layered shape memory films
摘要： Nano-layered films of PVAc/PU systems were fabricated by forced assembly coextrusion method. The bulk shape memory properties of PVAc/PU systems were utilized to program nanoscale patterns such as diffraction grating which exhibit iridescence after patterning. A hot embossing process has been utilized to imprint diffraction grating patterns as nano-scale information onto the surface of the thin multilayer films. Three levels of hierarchy i.e. layer thickness, spacing and heights of patterns, governs the functionality of the patterned multilayer film. The time and temperature dependent viscoelastic shape memory behavior determines the opto-mechanical tunability of the film. Mechanical switching of the patterns also leads to optical switching of the films which corresponds to their efficiency of information retrieval. The recovery of patterns as well as the diffractive property depends on the layer thickness (l) of films and heights of patterns (h0). The results illustrate that the higher ratio of h0/l better is the recovery of the grating patterns and the corresponding diffractive properties. This scaling effect enables versatile applications in information security by tuning the layer structure of the multilayer shape memory films.
关键词： scaling effect,shape memory film,pattern programming,hot embossing,multilayer film,information security,diffractive optical element,thermal responsive optics
更新于2025-10-22 19:40:53
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Numerical studies of residual states and scaling effects in laser-directed energy deposition additive manufacturing
摘要： Sequentially coupled thermo-mechanical model was used to simulate the residual stresses and residual distortions in the directed energy deposition additive manufacturing by laser. The proposed models were validated by comparison with experimental data. Different sizes of components were used to study the scaling effects. Results indicate that the residual stress can be controlled by the component sizes. This phenomenon can be explained by the bending deformation and the temperature fluctuations, especially the cooling rate, in the directed energy deposition additive manufacturing process. Both the bending deformation and the temperature fluctuations can be controlled by the ambient temperature and the designed process parameters. Analytical model was established to show how the components’ sizes affect the final residual states in combination with different design parameters.
关键词： Scaling effect,Residual stress,Residual distortion,Additive manufacturing
更新于2025-09-23 15:19:57