| Summary: | 碩士 === 正修科技大學 === 機電工程研究所 === 99 === The safety of plastic lenses has gained more attentions recently, how to enhance its impact safety is an important issue. Cryogenic treatment is an ultra-low temperature processing technique, which has been widely used in industry because this technique can be utilized to improve the wear resistance, dimensional stability and reduce the residual stress of materials. The purpose of this study was to practically investigate the effect of cryogenic treatment on plastic lenses as compared with the difference of material properties before and after this treatment. Experimental results demonstrated that the properties of untreated and cryo-treated plastic lenses were quite different. The untreated plastic lenses were easy to scratch, the plastic lenses almost showed no impact resistance and were all broken in the falling ball experiment. However, the wear resistance of cryo-treated plastic lenses was greatly enhanced and the impact resistance was also considerably increased. In addition, the cryo-treated plastic lenses showed less significant residual tensile and compressive stresses than the untreated plastic lenses from the stress polarization analysis. It is likely that the above-mentioned benefits are generally responsive to a more homogeneous and denser structure created after the cryogenic treatment. Further research needs to be conducted to explore the optimal cryogenic process and to elucidate the relationships between microstructure, cryogenic treatment and property of plastic lenses.
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