Definition of Rheology : Irreversible or not?

[hizballah_arham]

TL;DR Summary

I found definition of rheology to describe stress-strain processes of flow which irreversibly with time. But some of writers and groups use this term to describe reversible processes too. So what is exactly the true definition of rheology in fluid mechanics?

In Agricultural Process Engineering(Third Edition) by S.M. Henderson and R.L. Perry, Rheology is described as "... the science that considers stress-strain relations where flow proceeds irreversibly with time. Creep in metals and concrete and the strength properties of fruits and vegetables are examples. Strictly recognized, thixiotropic and rheopetic fluids are not rheological materials because there is no permanent deformation. Unfortunately, many writers and groups use the term rheology to include a variety of stress-strain processes that may or may not be time dependent or irreversible. The engineer should be aware that the term is frequently used to cover processes outside those in the definition."

My question is, does the definition of rheology truly only for irreversible processes when it's first stated? So does that mean the use of it for reversible processes it's not appropriate? Then why some writers and groups still using it despite that mistake, is it because there's no other term to be used to describe stress-strain relations of flow?

Just wanted to hear about your opinion and discuss about the topic. Thank you for clicking the thread!

 

[Chestermiller]

Rheology includes both reversible and irreversible material deformations. So it includes purely elastic material deformations. It is defined as the science of deformation and flow of materials.