The author measured surface tension coefficient for liquid with a new experimental apparatus, measured magnetic fluid surface tension coefficient at different temperatures and with different volume of surfactant. By the analysis of experimental data, we obtained that magnetic fluid surface tension coefficient decreases with the increasing temperature and increases with the addition of surfactant volume and reaches a certain stability value. We also obtained the expression of magnetic fluid surface tension coefficient and the temperature or surfactant. This paper discussed the relationship between the liquid surface tension coefficient and the temperature and surfactant from the view of thermodynamics.

Two different structure of dampers based on the principle of second-order buoyancy were designed in this paper. In order to verify the reduction of the vibration, a test rig was set up. On the test rig, the reduction effect of two different dampers was studied by adjusting the amount of the magnetic fluid. The experiment results indicate the relationship between the damping effect of magnetic fluid damper and the amount of magnetic fluid and this analysis result is benefit to the design of the dampers.

The erosion and wear mechanism for drilling equipment is studied in this paper, which is for the problem of unstable performance of drilling system and short lifetime caused by the erosion of drilling equipment by drilling fluid. The flow field, surface pressure of the erosion prone parts and drilling fluid flow rate are calculated by the finite element method. The results demonstrate the parts eroded seriously by drilling fluid appear in where the curvature of the curve of the wall changes suddenly and where the rate of change in the stress field is greater, which provide a theoretical basis on design, optimize, repair of drilling equipment.