gearbox.standards.agma2101._strength

Allowable stress adjustments of AGMA 2001-D04: Z_N, Y_N, C_H, K_R and K_T.

RELIABILITY_FACTORS = {'fewer than 1 failure in 10': 0.85, 'fewer than 1 failure in 100': 1.0, 'fewer than 1 failure in 1000': 1.25, 'fewer than 1 failure in 10000': 1.5, 'fewer than 1 failure in 2': 0.7}

Reliability factors K_R of table 11, by the number of failures allowed per 10^n units.

pitting_stress_cycle_factor(gear, cycles)

Stress cycle factor Z_N of figure 17 (general application line).

2.466 N^-0.056 (nitrided: 1.249 N^-0.0138) between 10^4 and 10^7 cycles, constant below 10^4, and 1.4488 N^-0.023 above 10^7. The lower edge of the shaded zone, used for critical service, has no formula in the standard and is not implemented.

Raises:

ValueError – If the gear is not made of steel.

Return type:

float

bending_stress_cycle_factor(gear, cycles)

Stress cycle factor Y_N of figure 18 (general application line).

Through-hardened steels interpolate on the Brinell hardness between the 160 HB and 400 HB curves (clause 17.2): linearly in ln Y_N at 10^3 cycles against ln HB, then a straight line on log-log axes to Y_N = 1.04 at 3 x 10^6 cycles. Above that, 1.3558 N^-0.0178.

Raises:

ValueError – If the gear is not made of steel.

Return type:

float

hardness_ratio_factors(transmission)

Hardness ratio factors (C_H pinion, C_H wheel), AGMA 2001-D04 clause 14.

C_H of the pinion is 1. For the wheel:

• through-hardened pair (14.1): 1 + A (m_G - 1) with A = 0.00898 HB_P/HB_G - 0.00829 for 1.2 <= HB_P/HB_G <= 1.7 (0 below, 0.00698 above);

• surface-hardened pinion against a through-hardened wheel of 180 to 400 HB (14.2): 1 + B (450 - HB_G) with B = 0.00075 exp(-0.0112 f_p), f_p being the roughness Ra of the pinion in microinches. Ra is estimated as Rz / 6 (ISO 6336-2 note).

Return type:

tuple[float, float]