McMillan D E, Utterback N G, Nasrinasrabadi M, Lee M M
Biorheology. 1986;23(1):63-74. doi: 10.3233/bir-1986-23105.
The rheology of blood is characterized by shear thinning, viscoelasticity, and thixotropy. Its rheological evaluation is usually accomplished using a torque balance technique during rotational viscometry. Because a stable torque balance does not develop instantly, studies of thixotropy and viscoelasticity of blood have usually been carried out only at low shear rate where their development is slow enough to be monitored accurately. The torque balance technique may be converted from static to dynamic by incorporating the rate of change of sensing system angular momentum. We have modified our Couette viscometer, adding a computer-controlled stepping motor and a second digital voltmeter. The latter is used to determine the angular position of the sensing system every 25 or 50 msec. The new approach allows rapid observation of the development and disappearance of shear stress, enabling us to examine the transient behavior of blood at moderate shear rate (1 to 100 inverse seconds). The transient flow behavior of blood at moderate shear rate is most easily compared directly with the behavior of Newtonian fluids. We present information about the response of our system using a torque balance observation rate of 20 per second. Blood's viscoelasticity is observed to fall substantially as shear rate rises, while its thixotropic transient excess stress rises steadily with increasing shear rate.
血液的流变学特性表现为剪切变稀、粘弹性和触变性。其流变学评估通常在旋转粘度测定过程中使用扭矩平衡技术来完成。由于稳定的扭矩平衡不会立即形成，因此血液触变性和粘弹性的研究通常仅在低剪切速率下进行，因为在低剪切速率下它们的形成足够缓慢，以便能够准确监测。通过纳入传感系统角动量的变化率，扭矩平衡技术可以从静态转换为动态。我们对我们的库埃特粘度计进行了改进，增加了一个计算机控制的步进电机和第二个数字电压表。后者用于每25或50毫秒确定传感系统的角位置。这种新方法允许快速观察剪切应力的形成和消失，使我们能够研究血液在中等剪切速率（1至100秒倒数）下的瞬态行为。中等剪切速率下血液的瞬态流动行为最容易直接与牛顿流体的行为进行比较。我们使用每秒20次的扭矩平衡观察速率展示有关我们系统响应的信息。观察到随着剪切速率的升高，血液的粘弹性大幅下降，而其触变性瞬态过应力则随着剪切速率的增加而稳步上升。
