MATERIAL, NEWTONIAN
Newtonian behavior (for viscous
materials): s µ e rate de /dt or s = (cont) de /dt :For
a viscous material, this constant of proportionality is m , the viscosity of
the material
MATERIAL, PLASTIC
The plastic material flows but is different from viscous materials since
it has some fundamental strength (the critical stress) which the viscous
fluid does not haveAlso, in ideally plastic materials, the strain takes
place in localized regions where the critical stress has been reached,
whereas, ideally viscous materials show deformation throughout the material
wherever a deviatoric stress is present Also called a firmoviscous response. Analog is spring and dashpot in
parallel. The dashpot causes the elastic response to be delayed so that the
elastic (recoverable) part of the response is time dependent both on loading
and unloading. Stress-strain relationship is linear with no fundamental
strength for the material.
MATERIAL, VISCOUS
The stress applied is directly proportional to strain rate. The
relationship is linear. stress = viscosity x strain rate; cgs units poise defined in stress strain rate space, the implied lack of fundamental
strength is notable. A material which is Newtonian viscous may start
behaving power law if the relation is nonlinear. Newtonian vs. power law e = µ s^3-5; for many rocks n=3-5 range. At atomic level or lattice, bond breakage and formation, and as things
get hot atom neighbor swapping accelerates. model is simple dashpot, no spring
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