当前位置: X-MOL 学术J. Rheol. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Oscillatory strain with superposed steady shearing in noncolloidal suspensions
Journal of Rheology ( IF 3.3 ) Pub Date : 2020-09-01 , DOI: 10.1122/8.0000072
Arif Mahmud 1 , Shaocong Dai 1 , Roger I. Tanner 1
Affiliation  

The rheology of noncolloidal suspensions in superposed simple shearing and oscillatory shearing was explored. With a Newtonian matrix fluid, one would expect that G′ would be zero in an oscillatory flow, but this was not found; the action of Coulomb friction between the particles appears to cause an increment of G′ at lower frequencies. To understand this frictional effect, measurements of small and medium strain oscillatory flows, up to 10% strain magnitude, were made. The matrix fluid was 12 Pa s silicone oil, and the polystyrene spheres were on average 40.3 μm in diameter. Hysteresis during tests with varying strain amplitudes was more dominant in the storage modulus than in the loss modulus, and, at a 50% volume fraction, the effect was severe. Because of the observed tendency to hysteresis, the oscillatory flow was then combined with a parallel steady shear flow to try to control or eliminate hysteresis. The hysteresis appears to be a frictional effect, and it was reduced under superposed shearing. The effect of variable oscillatory shear stress and steady shear stress was studied, and a model was proposed for the superposed storage modulus, loss modulus, and shear viscosity responses. Frictional effects are considered in the proposed model, and one observes a generally satisfactory fit to the experimental data. From the model, the average friction coefficient is shown to be less at higher frequencies due to higher relative rubbing speeds and better lubrication between the particles. Clearly, suspension rheology is dominated by friction and is essentially a study in tribology.

中文翻译:

非胶体悬浮液中叠加稳定剪切的振荡应变

研究了叠加的简单剪切和振荡剪切中非胶体悬浮液的流变学。对于牛顿基体流体,人们会期望 G' 在振荡流中为零,但事实并非如此;粒子之间的库仑摩擦作用似乎在较低频率下导致 G' 增加。为了理解这种摩擦效应,进行了高达 10% 应变幅度的中小应变振荡流的测量。基质流体为 12 Pa s 硅油,聚苯乙烯球平均直径为 40.3 μm。在具有不同应变幅度的测试期间,滞后在储能模量中比在损耗模量中更占主导地位,并且在体积分数为 50% 时,这种影响很严重。由于观察到的滞后趋势,然后将振荡流与平行的稳定剪切流相结合,以尝试控制或消除滞后现象。滞后现象似乎是一种摩擦效应,在叠加剪切下它会降低。研究了可变振荡剪切应力和稳态剪切应力的影响,并提出了叠加储能模量、损耗模量和剪切粘度响应的模型。在所提出的模型中考虑了摩擦效应,并且观察到对实验数据的总体令人满意的拟合。从模型中可以看出,由于较高的相对摩擦速度和颗粒之间更好的润滑,平均摩擦系数在较高频率下较小。显然,悬浮流变学主要是摩擦,本质上是摩擦学研究。
更新日期:2020-09-01
down
wechat
bug