rheology

Question 1

what is the dv/dr

Answer 1

the difference of velocity between 2 planes or liquid separated by infitesimal distance dr is the velocity gradient or rste of shear dv/dr

Question 2

what is shearing stress

Answer 2

the force per unit of area required to bring about flow

Question 3

what is relationship between force and viscosity

Answer 3

higher the viscosity the greater the rquired force per unit of area to bring about rate of shear

Question 4

kinematic velocity

Answer 4

absolute viscosity of a liquid divided by the density of a liquid at a specific temperature

Question 5

plastic flow

Answer 5

yield value
shearing stress corresponding to yv has to be achieved to cause flow
if lower than yield value it acts like elastic material
mobility; F-f/ G
contacts brought about by vdw need to be brocken before flow can begin.

Question 6

psuedoplastic

Answer 6

flocculated particles in suspensions
never linear start at orirgin
as stress is applied viscosity decreases
increase shearing vauses particles to align along the axes and in directional flow; reduced internal resistance leads greater rate of shear corresponding to shearing stress

Question 7

dilatant

Answer 7

dispersed solids high percentage
increase resisatnce with rate of shear
increases in volume ,, ,, ,,,
inverse of pseudoplastic

Question 8

thixotherapy

Answer 8

isothermal and comparitive recovery on standing of a material whose consistency has been lost by shearing

Question 9

resons for leaving newotonian flow

Answer 9

size of disoersed particles
packing of particles
phase volume ratio
orientation of dispersed phase