Page 43 - Tribology in Machine Design
P. 43
30 Tribology in machine design
In the case of heavily loaded contacts, plastic deformation of interacting
asperities is very likely. Therefore, it is desirable to determine the
probability of plastic asperity contact.
The probability of plastic contact may be expressed as
where plastic asperity deformation, <5 P, is calculated from
where r is the average radius of the asperity peaks, p m is the flow hardness of
1
the softer material and E' = [(l—v*)/E l + (l — vl)/E 2 ]~ . By normalizing
the expression for <5 P
and introducing the plasticity index, defined as
the normalized plastic asperity deformation, <5^, can be written as
Thus the probability of plastic contact is
