Abstract Powders are a special class of granular matter due to the important role of cohesive forces. Because the flow behavior of powders depends on both their flow states and confining stresses, it is difficult to measure/quantify with only one experiment. In this study, the most commonly used characterization tests that cover a wide range of states are compared: (static, free surface) angle of repose, the (quasi-static, confined) ring shear steady state angle of internal friction, and the (dynamic, free surface) rotating drum flow angle are considered for free flowing, moderately and strongly cohesive limestone powders. The free flowing powder gives good agreement of angles among all different situations (devices), while the moderately and strongly cohesive powders behave more interestingly. Starting from the flow angle in the rotating drum and going slower, one can extrapolate to the limit of zero rotation rate, but then observes that the angle of repose measured from the static heap is considerably larger, possibly due to its special history. When we stretch the ring shear test to its lowest confining stress limit, the steady state angle of internal friction of the cohesive powder becomes comparable with the flow angle (at free surface) in the zero rotation rate limit of the rotating drum test, by defining an appropriate effective stress.

中文翻译：

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扩展粘性石灰石粉末动态和准静态流动测试的极限

摘要 由于内聚力的重要作用，粉体是一类特殊的颗粒物质。由于粉末的流动行为取决于它们的流动状态和围压，因此仅通过一项实验很难测量/量化。在这项研究中，比较了涵盖广泛状态的最常用的表征测试：（静态，自由表面）休止角，（准静态，受限）环剪切稳态内摩擦角，以及（动态、自由表面）旋转鼓流动角被认为是自由流动的、中等和强粘性的石灰石粉末。自由流动的粉末在所有不同情况（设备）之间提供了良好的角度一致性，而中等和强粘性的粉末表现得更有趣。从转鼓中的流动角开始，走得更慢，可以推断到零转速的极限，但随后观察到，从静态堆测得的休止角要大得多，这可能是由于其特殊的历史。当我们将环剪试验拉伸到其最低围应力极限时，粘性粉末的稳态内摩擦角变得与转鼓试验零转速极限下的流动角（在自由表面）相当，通过定义适当的有效应力。