Effect of Different Shear Modes on Morphology and Mechanical Properties of Polypropylene Pipes Produced by Rotational Shear

Oriented “shish-kebab” structures could be obtained by shearing to enhance the mechanical properties of polymer samples markedly.However,the effect of shear mode on mechanical properties is still uncertain.The study of stepped hoop shear field on the isotactic polypropylene(iPP)pipe was developed through applying a self-designed rotational shear system(RSS).The effect of stepped shear field on the microstructure and comprehensive properties of iPP pipe was investigated by the comparison with continuous shear.It could be found that the loosely-assembled shish-kebabs with the larger size were formed in the continuous shear pipes,but the smaller and tightly-stacked ones existed in the pipes with stepped shear.Surprisingly,due to differential morphologies under different shear modes,better comprehensive mechanical properties were obtained in the pipes with stepped shear.

Discrete element method study of shear-driven granular segregation in a slowly rotating horizontal drum

Segregation and mixing of granular materials are complex processes and are not fully understood. Motivated by industrial need, we performed a simulation using the discrete element method to study size segregation of a binary mixture of granular particles in a horizontal rotating drum. Particles of two dif- ferent sizes were poured into the drum until it was 50% full. Shear-driven segregation was induced by rotating the side-plates of the drum in the opposite direction to that of the cylindrical wall. We found that radial segregation diminished in these systems but did not completely vanish. In an ordinary rotating drum, a radial core of smaller particles is formed in the center of the drum, surrounded by larger revolving particles. In our system, however, the smaller particles were found to migrate toward the side-plates. The shear from anti-spinning side-plates reduces the voidage and increases the bulk density. As such, smaller particles in the mixer tend to move to denser regions. We varied the shear by changing the coefficient of friction on the side-plates to study the influence of shear rate on this migration. We also compared the extent of radial segregation with stationary side-plates and with side-plates moving in different angular directions.

Shears bands in ^(112)In

A new level scheme of 112In have been established up to 6.8 MeV in excitation energy and to a tentative spin of (21+) through the reaction 110Pd(7Li,5n)112In at a beam energy of 50 MeV. In-beam measurements involving γ-γ coincidences and directional correlation of oriented states were performed. M1 bands consisting of I =1 dipole transitions have been observed. Possible quasiparticle configurations suggest that these bands are similar to the shears bands observed in Pb nuclei.

Dynamics of Attractive Vesicles in Shear Flow

A nonequilibrium molecular dynamics（NEMD） method is employed to study the dynamics of two identical vesicles with attractive interactions immersed in shear flow. The dynamics behaviors of attractive vesicles depend on the attractive interactions and the shear rates simultaneously. There are four motion types for attractive vesicles in shear flow： a coupled-tumbling（CTB） motion, a coupled-trembling（CTR） motion, a collision/rotation mixture（CRM） motion and a separated-tank-treading（STT） motion, which are determined by the competition between the shear flow and the attractive interactions. Furthermore, the dynamics behavior of an individual vesicle shows three main motion types such as tumbling, trembling and tank-treading motions, and relies mainly on the shear rates. Meanwhile, comparisons with rigid vesicles for the dynamics behaviors are made, and the collision/rotation mixture（M） motion isn＇t observed for rigid vesicles.