Abstract
Our group collaborates with the National Palace Museum in Taipei, Taiwan on a problem that has been existed for thousands of years. Qi-Wa, a Chinese phrase, means the up curl on the edge of the scrolls. It not only decreases the value in aesthetics, but also incurs damage on the scrolls. In order to preserve the painting, it is important to alleviate the deformation. In this thesis, we construct four models to explain Qi-Wa phenomenon to different types of scrolls and try to understand their physical mechanism. We find Qi-Wa height to follow simple scaling laws and check these relations by experiment and Molecular Dynamics(MD) simulations. Furthermore, we propose ways to mitigate the Qi-Wa under conditions that will not violate the traditional and aesthetic standards. On the second part of the thesis, we discuss a more severe type of deformation on the thin sheets; namely. the daily phenomenon of crumpling. We will focus on the crumpling of two different sheets together. There are a lot of properties that have been found in the crumpled single sheet. For example, the external force and the crumpled ball radius $R$ obey a scaling relation and the ridge length follows the log-normal distribution. However, there are no studies on whether these properties exist when we crumple two different materials together. Furthermore, how does the energy distribute on the two separate sheets when the compaction increases? Can we explain their behavior by the concept of thermodynamic temperature? What's the role of the ridge-ridge interactions? We use the MD simulation as a tool to solve these questions. We find that some scaling laws still hold in the co-crumpling system except their exponents are changed. For instance, the force and the $R$ still obey the power-law relation in co-crumpling but the exponent of the co-crumpling will be different from the exponent of single sheets. Besides, we can explain some results by the mean-field approximation.