Question

Two contacting rollers used for a machine application. They run together with a combination of rolling and 9% sliding. The resulting maximum compressive principal stress in the contact zone is 16500 psi. Both rollers are made from 6061-T6 hard anodized aluminum. The design life of the rollers is 3.5 years of 2-shift operation at 260 days/year and they each turn at 220 rpm. What is the expected safety factor against pitting for the roller pair?

Answer 1

SOL =9% sliding mal. Given data :- TWO contacting rollers used for a machine application , Rollers made of 6061-T6 hard rolling anodized aluminium compressive principal stress Coz] - 16500 psi design life of the rolleys - 3-5 years of d - shift operation 260 day/year Speed Therefore, from the properties of aluminium table young's moduluq CE) = 1•039x107 psi poisson's ratio cou) = 0.34 material constant - M m,- M2 1-0.347 T.039 x 107 220 rpm E = 0.8512 X 10 psi from the table , surface fatigue strength data of various materialą for rolling and 9% sliding , against 6061-T6 hard anodized aluminium Slope factor (a) = 5:02 Intercept facfor ($) = 20.12

.: required cycle life cycles : 220 X 60 X 24 X 260 X 3.5 = 2.88X108 Therefore k factor for compressive mat: normal stress k = T mit m2.07 .. K = TTC 0.8512x107 1+0 0.8512x107 Psi ] [165003 psi = 145.606 psi .: k = 145.606 psi no. of cycles Ś - Log CNufe) a (542209CK)] Nlife (20.12 - 5.02x log C145-606)) Log Ck) - 10 - 10 = 1.823x109 . Nlife = 1.823x109 Therefore, safety factor against pitting (NG) - NLife cyclez 1.823 x109 = 2.88 x 108

Nf = 6.329 Therefore, the safety factor against pifting NF = 6-329