Fall Abdoulaye, Huang N, Bertrand F, Ovarlez G, Bonn Daniel
Laboratoire de Physique Statistique de l'ENS, 24, rue Lhomond, 75231 Paris Cedex 05, France.
Phys Rev Lett. 2008 Jan 11;100(1):018301. doi: 10.1103/PhysRevLett.100.018301. Epub 2008 Jan 8.
We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits shear thickening. From magnetic resonance imaging velocimetry and classical rheology it follows that as a function of the applied stress the suspension is first solid (yield stress), then liquid, and then solid again when it shear thickens. For the onset of thickening we find that the smaller the gap of the shear cell, the lower the shear rate at which thickening occurs. Shear thickening can then be interpreted as the consequence of dilatancy: the system under flow wants to dilate but instead undergoes a jamming transition because it is confined, as confirmed by measurement of the dilation of the suspension as a function of the shear rate.
我们研究了玉米淀粉悬浮液的流变学,这是一种表现出剪切增稠的非布朗粒子系统。从磁共振成像测速法和经典流变学可知,随着外加应力的变化,悬浮液先是呈固态(屈服应力),然后变为液态,当发生剪切增稠时又再次变为固态。对于增稠的起始阶段,我们发现剪切池的间隙越小,发生增稠的剪切速率就越低。然后,剪切增稠可以被解释为剪胀的结果:流动状态下的系统想要膨胀,但由于受到限制反而经历了堵塞转变,这一点通过测量悬浮液的膨胀随剪切速率的变化得到了证实。