The Stribeck curve describes the friction of flat surfaces while the orientation of clay suspensions in a rheology experiment is not always defined. Is there nonetheless a mathematical ( physical) relation?
To clarify, are you aiming to describe frictional/lubrication behavior between clay particles using the Stribeck curve concept, or interpret a Stribeck curve for clay suspensions between another contact pair (e.g. metal surfaces)?
We certainly need clarification. Are you interested in the lubricating properties of clay? That is all the Stribeck curve will tell you.
If you want to know about the effect of platelet orientation on the rheology - that is another story. I worked with Christophe Baravian (RIP) on a rheo-optical method to measure the orientation of anisotropic particles and incorporate it into a rheological model. See lots of papers via "Baravian clay" in Google Scholar. "Baravian Dillet" gives you applications to red blood cells and surfactant disks.
- Searching on "Baravian Vantelon" gives a 2003 paper that shows how to use rheology data to get the orientation of clay disks and their interaction potential.
- Searching on "Blachier Baravian" gives a recent paper (Jan 2014) on the same theme, showing how powerful the modelling can be.
Thanks (esp. to AP): That comes closer to what we are looking at now. We do relatively low concentrations (say 18g/L). We also look at smaller disks, i.e. LRD products. Funnily, we get non-monotonic dependencies when doing viscosity as shear rate. Also similar results with oscillatory shear. Did not do plots in your manner (or Baravian's). So basically, I get much further now. If you also have a hint for non-monotonic behavior - that would be appreciated much. I agree that I need to read more of the related papers.
Stribeck just gave me an idea for more complicated behaviors. As I understand Baravian now, it is purely orientation, and Stribeck friction is not essential for the rheology.