The question of whether Carbopol gels always behave as “model” yield stress material is addressed experimentally. Prompted by several simple hydrodynamic experiments performed with Carbopol gels that can not be fully understood within the commonly accepted “model” picture, we revisit the yielding behaviour of a Carbopol gel. When subjected to a loading/unloading process, the yielding of the Carbopol is gradual and exhibits a rheological hysteresis. By in-situ visualisation of the microstructure it is demonstrated that these features do not originate from a micro-structural damage of the micro-gel. A systematic description of the role of the rate at which the material is forced (loaded or unloaded) on the yielding scenario is given. In closing, the question of how simple a scalar model can be and yet accurately describe the experimentally observed yielding scenario of a Carbopol gel in a rheometric flow is addressed. It is concluded that simple scalar models may do such job as long as they are not too simple and include a minimal amount of physical ingredients.

通过实验解决了Carbopol凝胶是否始终表现为“模型”屈服应力材料的问题。由使用Carbopol凝胶进行的几个简单的水动力实验提示，在公认的“模型”中无法完全理解图片，我们重新审视了Carbopol凝胶的屈服行为。当进行装载/卸载过程时，Carbopol的产量是逐渐变化的，并表现出流变滞后性。通过微结构的原位可视化证明，这些特征不是源自微凝胶的微结构破坏。给出了在屈服场景下材料被迫（加载或卸载）速率的作用的系统描述。最后，提出了一个简单的标量模型，但仍能准确描述流变流中Carbopol凝胶的实验观察到的屈服情形的问题。结论是，只要简单的标量模型不太简单，并且包含最少的物理成分，它们就可以完成此工作。