Optimal conditions for pre-shearing thixotropic or aging soft materials
Optimal conditions for pre-shearing thixotropic or aging soft materials
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DOI：
10.1007/s00397-020-01250-4
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发表时间：
2020-10-20
期刊：
影响因子：
2.3
通讯作者：
Rogers, Simon A.
中科院分区：
文献类型：
--
作者：
Choi, Jiho;Rogers, Simon A.
预剪切被广泛认为是保证触变或老化软材料流变学研究可重复性的必要步骤。当使用单向预剪协议时，未恢复的弹性应变导致材料状态偏差，由于松弛过程中结构的积累而不总是松弛。我们提出了一种保证无偏材料状态的方法，通过将恢复步骤，包括反对剪切初始方向的应变步骤，纳入任何预剪切协议。使用这种多步预剪协议，我们表明，在预剪后的相同速率下，在正、负方向剪切可以产生相同的结果。我们进一步展示了如何使用这种无偏材料状态的想法来获得其他基本流变实验的无偏结果，如流动曲线和频率扫描。通过对流动曲线或频率扫描的每个测点执行新的预剪切协议，可以获得不受先前数据收集影响的数据，从而获得具有简单而清晰的剪切历史的材料响应。
Pre-shearing is widely recognized as a necessary step to guarantee repeatability in rheological studies of thixotropic or aging soft materials. When one-directional pre-shear protocols are used, unrecovered elastic strain which leads to biased material states that are not always relaxed because of the build-up of structure during the relaxation process. We propose a way of guaranteeing unbiased material states by incorporating recovery steps, consisting of steps of strain opposing the initial direction of shearing, into any pre-shear protocol. Using such a multi-step pre-shear protocol, we show that it is possible to produce identical results from shearing in the positive and negative directions for the same magnitude of rate after pre-shearing. We further show how this idea of unbiased material states can be used to obtain unbiased results for other fundamental rheological experiments such as flow curves and frequency sweeps. By performing the new pre-shear protocol for every single measurement point of a flow curve or frequency sweep, it is possible to obtain data which is not affected by previous data collection, which leads to material responses with simple and clear shear histories.