复合水凝胶力学行为研究中应力-应变循环压缩曲线滞后形状变化的动力学
Dynamics of the variation of shape of the hysteresis of stress-strain cyclic compression curves registered at the investigations of the mechanical behavior of composite hydrogels
摘要：
在多次循环压缩测试条件下研究膨胀水凝胶组合物“纤维素-聚丙烯酰胺”时，发现了一种不寻常的机械行为，其变形速度变化很大。随着变形速度的增加，循环应力-应变曲线的压缩段和减压段的位置明显倒置。当以较低的变形速度（约为初始试样高度的100- 200%/min）进行循环压缩试验时，可以看到应力-应变曲线的明确滞后，在这些条件下，曲线的减压部分位于压缩部分的下方。但是，随着变形速度的增加，可以清楚地看到压缩和减压曲线彼此逐渐接近的趋势。这种效应的结果在完全消失的滞后在某一值的变形速度：减压曲线与压缩曲线重合。随着变形速度的进一步提高，滞后现象又出现，但压缩过程的滞后曲线位于减压过程的滞后曲线的下方，滞后现象出现“反转”。该过程的精确特征取决于所研究的水凝胶的刚度。到目前为止，对这种效应还没有令人信服的解释。作者只能提出一些假设来解释这一现象。
英文摘要：
An unusual type of mechanical behavior was registered while studying the swollen hydrogel compositions "cellulose-polyacrylamide" in the conditions of multiple cyclic compression tests with the broad variation of the deformation speed. While increasing the deformation speed the clearly seen inversion of the positions of compression and decompression parts of the cyclic stress-strain curves was detected. While carrying out the cyclic compression tests with relatively low deformation speed (about 100-200 % of the initial sample's height per minute) the well defined hysteresis of the stress-strain curve can de seen and in these conditions the decompression part of the curve is situated inferior the part corresponding to compression. But while increasing the speed of the deformation the tendency to the progressive approach of the compression and decompression curves to each other is clearly seen. This effect results in the full disappearance of the hysteresis at some value of the deformation speed: the decompression curve coincides with the compression curve. Along with the further increase of the deformation speed the hysteresis appears again but the curve corresponding to compression process is situated inferior the curve corresponding to decompression: the "inversion" of the hysteresis was detected. The precise character of this process depends upon the stiffness of the hydrogel under study. Up to date the convincing explanation of this effect can not been put forward. The authors can only present some hypotheses to explain this phenomenon.
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