We study effect of addition of graphene on mechanical properties (elastic modulus and Poisson's ratio) of hydroxyapatite composites. Firstly, generating algorithm of random distribution geometric model of graphene/hydroxyapatite composites was created and model's automatic generation program was developed. Then, finite element model of graphene/hydroxyapatite composite was established. Finite element analysis of uniaxial tensile tests of composite materials was carried out. Finally, mechanical properties of different mass fraction of graphene of composite were calculated. Validity of the algorithm is verified by experimental data. It shows that elastic modulus of composite increased 12% to 50% with addition of 0.25% to 1.25% (wt.) graphene. Mechanical properties of hydroxyapatite can be effectively improved by addition of graphene.

Wind sand flows affect surface electric field and potential on insulators. We established a gas-solid flow model for insulator surrounded by sand and a sand-electricity coupling model made up of high voltage insulator based on finite volume method (FVM). Spatial distribution and deposition of sand on surface of insulator and electric field distribution along insulator under different wind sand flow are calculated. It shows that surface potential and electric field distortion are influenced obviously by wind speed and particle size. Distortion of electric potential increases with increase of wind speed and particle size, while distortion of electric field decreases with increase of wind speed and particle size. Different spatial distribution and deposition of sand make different distortion on potential and electric field along insulator.