An innovative experimental apparatus for the direct measurement of yield stress was conceived and realized. It is based on a torsion pendulum equipped with a magnetic dipole and a rotating cylinder immersed in the material to be investigated. The pendulum equilibrium state depends on the mechanical torque applied due to an external magnetic induction field, elastic reaction of the suspension wire, and shear yield stress. Experimental results are reported showing that the behavior of the pendulum rotation angle, in different equilibrium conditions, provides evidence of the yield stress presence and enables its evaluation by equilibrium equations. The dependence on time of the equilibrium approach was also studied, contributing to shed light on the relaxation effect in the transition from a fluid-like to solid-like behavior, as well as on the eventual thixotropic effects in non-Newtonian fluids. The validity of the proposed technique and related experimental apparatus was tested in aqueous Carbopol solutions, with different weight percentages. The linear procedure, combined with the effectiveness and reliability of the proposed experimental method, candidates it to be used for the study of peculiar behaviors of other yield stress complex fluid such as blood, crude waxy oils, ice slurries, and coating layer used in the food industry and also for fault sliding in geodynamics.

设计并实现了一种直接测量屈服应力的创新实验装置。它基于扭摆，该扭摆配备有磁偶极子和浸入待研究材料的旋转圆柱体。摆平衡状态取决于由于外部磁感应场施加的机械扭矩，悬索的弹性反应和剪切屈服应力。实验结果表明，摆锤旋转角在不同平衡条件下的行为提供了屈服应力存在的证据，并能够通过平衡方程进行评估。还研究了平衡方法对时间的依赖性，有助于阐明从流体行为到固体行为转变中的弛豫效果，以及最终在非牛顿流体中的触变效应。在不同重量百分比的Carbopol水溶液中测试了所提出技术和相关实验设备的有效性。线性程序，结合所提出的实验方法的有效性和可靠性，可用于研究其他屈服应力复合流体的特殊行为，例如血液，粗蜡油，冰浆和用于该系统的涂层。食品工业以及地球动力学中的断层滑动。