关于Cox-Merz规则的有益讨论

我之前从一篇paper出发讨论过我对Cox-Merz规则的看法。我在LinkedIn的Society of Rheology群里也曾经发起过相关讨论,现在这个讨论很长了,而且出现了一些让我获益良多的回复。例如:

I think the main “killer” of CM is when the (large) strains in a steady state measurement start to modify the structure. So colloidal & thixotropic systems, gels can be problematic. If the system can be assumed to be robust under large strains, like polymer solutions, low molar mass fluids then CM works quite well. I have always interpreted CM as “there is only one obvious time scale”: for steady state 1/shear rate, for dynamic 1/frequency. Rheology is not much more than forcing a time scale onto the system.The physics takes care of the rest (OK,OK = leap of faith). If the material does not withstand steady state strains of 1-100 or so without changing its local structure then you have a problem. From a physics point of view I am still not sure whether I like eta* as a concept, one might argue that the viscosity of a steel bar is quite small (i.e. totally elastic) but of course it does not creep noticeably so then viscosity is “infinite”. Would be happy to discuss this further, it is one of those nagging problems that you apparently have to live with.