Dry Friction

t

30.

m

1.

c

1.

F

0

1.

v

0

0.5

x(0)

1.297

x'(0)

0.5

The phenomenon of dry friction (or Coulomb friction) occurs when the surfaces of two dry, unlubricated solids move past one another. The plots illustrate a model for dry friction: a mass

m

attached to a spring with stiffness

c

moves over a continuous belt traveling at constant speed

v

0

, with the frictional force

F=

F

0

sgn(

v

0

-

′

x

)

. The position of the mass is shown as a function of time

t

and also plotted against

x'(t)

. The effect of dry friction on machine operation is an important consideration in mechanical engineering.