PSI - Issue 46

Robert Basan et al. / Procedia Structural Integrity 46 (2023) 62–67 Robert Basan et al. / Structural Integrity Procedia 00 (2019) 000–000

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Table 2. Gears’ material condition and hardness, loading and estimated coefficient of friction in mesh. Parameter Gear pair 1 Gear pair 2 Gear pair 3 Gear pair 4 material and condition 42CrMo4, Q&T 42CrMo4, Q&T 42CrMo4, Q&T 42CrMo4, Q&T yield stress, R e (Nmm -2 ) 540 627 872 961 Brinell hardness, HB (HB) 215 240 310 325 total normal force, F bt (N) 2696 3204 4527 5061 coefficient of friction, estimated 0,04

Values of Vickers hardness given in the study were recalculated to Brinell hardness using the expression (6):

(6)

5000 2407,5 5752500   

HB

HV

Values of individual strain-life fatigue parameters determined for the material of every analyzed gear pair using expressions (2) and (3) are given in Table 3.

Table 3. Values of Basquin-Coffin-Manson fatigue parameters estimated from Brinell hardness. Parameter Gear pair 1 Gear pair 2 Gear pair 3

Gear pair 4

material and condition Brinell hardness, HB (HB)

42CrMo4, Q&T 42CrMo4, Q&T 42CrMo4, Q&T 42CrMo4, Q&T

215

240

310

325

fatigue strength coefficient,  f '/ E (-) fatigue strength exponent, b (-) fatigue ductility coefficient,  f ' (-) fatigue ductility exponent, c (-)

0,00491 -0,087 0,9605 -0,670

0,00537 -0,0842

0,00667 -0,0788 1,0157

0,0069 -0,078 0,9707 -0,733

1,031

-0,6866

-0,726

Experimental and fatigue lives calculated using estimated fatigue parameters were compared through ratios of fatigue lives of individual gear pairs and maximum fatigue life of particular gear pair (gear pair 3 in experimental study and gear pair 4 in calculations). From diagram in Figure 2 it can be seen that increase in hardness of gear teeth flanks’ material results in increased experimental fatigue lives of tested gear pairs. Calculated fatigue lives follow this change very closely with minor deviation notable only between materials with small differences in hardness (310 HB and 325 HB).

2 N f,exp /2 N f,exp_max 2 N f,calc /2 N f,calc_max

Brinell hardness of gear pairs teeth flanks, HB (HB)

Fig. 2. Comparison of relative experimental and calculated fatigue lives (2 N f /2 N f, max ) of tested gear pairs’ teeth flanks.