friction in metal forming:

Explain couolomb friction
Explain the friction model that is known as constant shear or shear friction model
Explain what the ring test is, how it is undertaken and what it it used to measure

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Request for Question Clarification by aditya2k-ga on 12 Nov 2002 04:12 PST

Hi,

  How much explanation will you need? Is this enough for coulomb
friction?

Coulomb Friction
----------------
In the Coulomb friction model, two contacting surfaces can carry shear
stresses up to a certain magnitude across their interface before they
start sliding relative to each other. This state is known as sticking.
The Coulomb friction model defines an equivalent shear stress T (tau)
, at which sliding on the surface begins as a fraction of the contact
pressure p ( T = µp + COHE, where  µ is the friction coefficient and
is defined as a material property, and COHE specifies the cohesion
sliding resistance). Once the shear stress is exceeded, the two
surfaces will slide relative to each other. This state is known as
sliding. The sticking/sliding calculations determine when a point
transitions from sticking to sliding or vice versa. The coefficient of
friction can be any non-negative value.

In the metal forming process,
B := mu/tan(alpha);
Model_EqF := ((1+B)/B)*(1-(1/R)^(2*B)) +
(sigma[xb]/sigma[0])*(1/R)^(2*B);

I cannot show graphical displays here, but if you visit
http://www.mapleapps.com/categories/engineering/manufacturing/html/metal1.html,
a graphic of the euqations can be seen. This will make it more clearer
for you



Regards,
aditya2k