岩石试件端面摩擦效应数值模拟研究

NUMERICAL SIMULATION OF THE END FRICTIONAL EFFECT OF ROCK SPECIMENS

试件端面摩擦效应直接影响试件内的塑性等效应变、侧向位移的分布和单元应力应变曲线。本文运用ANSYS中的接触单元模拟了平面应变状态下端面摩擦效应对塑性等效应变、侧向位移和单元应力应变曲线的影响,得到了不同摩擦系数时塑性等效应变及侧向位移的渐进变化形式。当接触面摩擦较小时,塑性等效应变图案为上下两个X形网络,侧向位移上下分布均匀;当接触面摩擦增大时,塑性等效应变网络向中部靠拢并且明显增大,侧向位移上下分布不均匀,中部较上下端面位移大;当试件端面侧向位移被限制,即摩擦力很大时,塑性等效应变网络变为一个X形局部化带,侧向位移分布更加不均匀,中部明显隆起。

The end frictional effect of a specimen can influence the plastic equivalent strain, lateral displacement and element stress-strain curve in the specimen. This paper presents gradual change forms on plastic equivalent strain and lateral displacement in various frictional coefficients, which are obtained from the simulation of the influence of the end frictional effect on a plastic equivalent strain, lateral displacement and element stress-strain curve in a plane strain using contact element in ANSYS. When friction is the minimum on the contact plane, the plot of plastic equivalent strain is two X-shaped localization bands from the upper to the lower end with a uniform distribution of lateral displacement. When friction is large on the contact plane, the plastic equivalent strain localization bands increase greatly and move towards the middle of the specimen. At the same time, the lateral displacement distribution is not uniform and the displacement in the middle is larger than those near the two ends. When the lateral displacement is restricted at both ends of the specimen, i.e., the friction is very large, the plot of plastic equivalent strain change to one X-shaped localization band, the lateral displacement distribution becomes even less uniform, and large dilation occur in the middle of the specimen.