Universal behavior related to continuous symmetry breaking in nematic liquid crystals is studied using Brownian molecular dynamics. A three-dimensional lattice system of rod-like objects interacting via the Lebwohl-Lasher interaction is considered. We test the applicability of predictions originally derived in cosmology and magnetism. In the first part we focus on coarsening dynamics following the temperature driven isotropic-nematic phase transition for different quench rates. The behavior in the early coarsening regime supports predictions made originally by Kibble in cosmology. For fast enough quenches, symmetry breaking and causality give rise to a dense tangle of defects. When the degree of orientational ordering is large enough, well defined protodomains characterized by a single average domain length are formed. With time subcritical domains gradually vanish and supercritical domains grow with time, exhibiting a universal scaling law. In the second part of the paper we study the impact of random-field-type disorder on a range of ordering in the (symmetry broken) nematic phase. We demonstrate that short-range order is observed even for a minute concentration of impurities, giving rise to disorder in line with the Imry-Ma theorem prediction only for the appropriate history of systems.
COBISS.SI-ID: 20050952
In this work an influence of Young’s modulus on deflection of polymer gear tooth with no permanent set was presented. Deflection was determined with finite element method. Results show that it is very important to determine accurate value of Young’s modulus. Accurate determination of Young’s modulus can be questionable when it is determined using results of stress strain presented in diagram from literature. In this case it is better to use appropriate strain energy potential of hyperelastic constitutive law.
COBISS.SI-ID: 16850966