THE PLASTICITY OF SOLIDS

219

/

r

"J

extrapolating the curve to the axis; the value of the intercept
will eviclently be the friction. We may also use the algebraical
method. In either case at least two measurements of the rate
of flow V^/ti = v\ and Vz/tz = v2 are necessary corresponding to

0.025

0.020

0.015

O.OIO

0.005

/

/

JJ.

//

f

500

1500

2000

1000
Shearing Stress
FIG. 78. - IFlow-shear curves of a certain paint, using capillaries of varying
length and radius.
the shears FI and Ft, respectively. Assuming that the mobility
is independent of the rate of flow, Eq. (73) integrated in Eq. (89)
gives us