The frost-salt resistances of concrete were investigated according to the CDF methodeffects of air void systems introduced by different air entraining agent. The results showed that the frost-salt resistance of concrete increased with the decreasing of spacing factor and increasing of air content. The speed of frost-salt scaling of concrete was reduced when the spacing factor less than 0.200mm. The results also showed that the frost-salt resistance of concrete of different surface exist difference. The frost-salt resistance of concrete can improve by controlling of the spacing factor not the air content.
The dependence of the static friction force exerted on a rod immersed in granular matter on the filling height of granules and the diameter of the rod is studied experimentally. It is observed that the friction force increases with the filling height of granules and increasing diameter of the rod. A model based on the continuous media is given, which can explain the observed results. It is demonstrated that the friction force is proportional to the diameter of the rod and the square of the filling height in the case of shallow granules, while it is a linear function of the filling height in the case of very deep granules,i.e. the friction force is proportional to the area of the interface between the rod and granules.
Analytic calculation and Finite Element Method simulation are used to research the relationship between friction and bitten condition in cold ring rolling. It is found: if the ring can ’t be bitten in groove, rolling process will be stopped. The rolling force will increase rapidly, which will cause the breakage of rolls and equipment. When the feed velocity and other technical parameters are kept unchanged, the bitten condition will be disappeared with the process of ring rolling even if the ring can be bitten at the beginning stage.
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