科研之友
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摘要
Wall slip occurs under large amplitude oscillation shear (LAOS) for yield stress fluids. In this work, we investigated how the boundary conditions affect the nonlinear behavior under LAOS and proposed a simple methodology based on the geometric average of Lissajous curves to study the dynamic wall slip behavior under oscillatory shear. The results show that the stress-mean strain curve is a good candidate to define material's functions since it is almost not influenced by the wall slip effect. Meanwhile, the stress-mean strain rate curves from smooth plates and rough plates can be used to determine the wall slip velocity. It is found that the intercycle maximum slip strain rate follows the generalized Navier's law, while the intracycle slip behavior can be well described by a Maxwell-like dynamic slip model, which helps to determine the slip relaxation time. It is also found that the slip Deborah number is independent of the angular frequency and is a monotonically decreasing function of the reduced stress. Moreover, the slip Deborah number depends on the reduced stress through a power law, and there is an evident transition of the power law exponent at the yield stress.
- 出版日期2017-7
- 单位上海交通大学
