gearbox.standards.iso6336._load_factors

Load factors of ISO 6336-1 (method B): dynamic, face and transverse load factors.

The functions here are shared by the pitting (ISO 6336-2) and bending (ISO 6336-3) calculations. Formula numbers refer to ISO 6336-1:2019. Entries marked KNOWN-ISSUE KI-nn reproduce behaviour of earlier releases that still deviates from the standard (see KNOWN_ISSUES.md).

class MeshStiffness

Bases: object

Stiffness values of the tooth mesh (ISO 6336-1, clause on mesh stiffness).

single_stiffness: float

c', single tooth-pair stiffness [N/(mm um)].

mesh_stiffness: float

c_gamma_alpha, average mesh stiffness [N/(mm um)].

face_mesh_stiffness: float

c_gamma_beta = 0.85 c_gamma_alpha.

__init__(single_stiffness, mesh_stiffness, face_mesh_stiffness)

class LoadFactors

Bases: object

All load factors of ISO 6336-1 for one load case.

dynamic_factor: float

K_v.

face_load_factor_contact: float

K_H_beta.

face_load_factor_root: float

K_F_beta.

transverse_load_factor_contact: float

K_H_alpha.

transverse_load_factor_root: float

K_F_alpha.

__init__(dynamic_factor, face_load_factor_contact, face_load_factor_root, transverse_load_factor_contact, transverse_load_factor_root)

mesh_stiffness(transmission)

Single and mesh stiffness, method B of ISO 6336-1 (clause 9.3).

c' = c'_th C_M C_R C_B cos(beta) (82), extended to dissimilar materials by (90)-(91) and to line loads below 100 N/mm by (92); c_gamma_alpha = c' (0.75 eps_alpha + 0.25) (93) and c_gamma_beta = 0.85 c_gamma_alpha (94). C_R is taken from the pinion.

Parameters:

transmission (Transmission) – The gear pair.

Returns:

The MeshStiffness of the pair.

Return type:

MeshStiffness

class ProfileDeviations

Bases: object

Effective deviations of the pair after running-in (ISO 6336-1, formulae 18 and 19).

base_pitch: float

f_pb, the larger base pitch deviation (f_pt may be used) [um].

base_pitch_allowance: float

y_p = y_alpha [um].

profile_form: float

f_f_alpha, the larger profile form deviation [um].

profile_form_allowance: float

y_f [um].

property effective_base_pitch: float

f_pb,eff = f_pb - y_p.

property effective_profile_form: float

f_f_alpha,eff = f_f_alpha - y_f.

__init__(base_pitch, base_pitch_allowance, profile_form, profile_form_allowance)

profile_deviations(transmission)

Governing profile deviations of the pair and their running-in allowances.

Return type:

ProfileDeviations

dynamic_factor(transmission)

Dynamic factor K_v by the method selected in the transmission.

A value given in Transmission.measured_dynamic_factor (Method A) is used as it is.

Return type:

float

dynamic_factor_method_c(transmission)

Dynamic factor K_v, method C of ISO 6336-1 (clause 6.6.3, formulae 35 to 38).

K_v = 1 + (K1 / (F_t K_A K_gamma / b) + K2) (v z1 / 100) K3 sqrt(u^2 / (1 + u^2)) with K1 and K2 from table 11 for the worse tolerance class of the pair. Helical gears with eps_beta < 1 interpolate linearly between the spur and the helical value (35). The line load is not taken below 100 N/mm.

Raises:

ValueError – If the tolerance class is not an integer from 3 to 11.

Return type:

float

running_in_tip_relief(gear)

Tip relief C_ay produced by running-in [um], ISO 6336-1:2019 table 8, note 1.

C_ay = (sigma_Hlim / 97 - 18.45)^2 / 18 + 1.5, figure 3.

Return type:

float

dynamic_factor_method_b(transmission)

Dynamic factor K_v, method B of ISO 6336-1.

Raises:

ValueError – For an internal wheel: clause 6.5.9 gives the reduced mass of pairs with external teeth only.

Return type:

float

shaft_deformation_equivalent_misalignment(transmission, load_per_width)

Equivalent misalignment f_sh of pinion and shaft [um], ISO 6336-1 7.5.3.5.2.

Formula (59) for spur and single helical gears; formula (60) for double helical gears, with b_B the smaller helix width of the pair, 2 k_unit and B* = 1.5 (all the power through a single engagement), where F_m / b refers to the total width b = 2 b_B.

Parameters:

• transmission (Transmission) – The gear pair.

• load_per_width (float) – F_m / b [N/mm].

Return type:

float

face_load_factor_contact(transmission)

Face load factor for contact stress K_H_beta, method C of ISO 6336-1 (clause 7.5).

The initial equivalent misalignment F_beta_x is built from the shaft deformation f_sh (59) and the mesh misalignment f_ma (66) with formulae (54) or (55), bounded below by F_beta_x,min (58); running-in (45)-(53) gives F_beta_y and formulae (41)-(44) the factor. Double helical gears use b_B and formula (60) for f_sh, and F_m / b with b = 2 b_B.

Parameters:

transmission (Transmission) – The gear pair.

Returns:

K_H_beta (>= 1).

Return type:

float

face_load_factor_root(transmission)

Face load factor for tooth-root stress K_F_beta (ISO 6336-1).

Return type:

float

contact_ratio_factor(transmission)

Contact ratio factor Z_epsilon (ISO 6336-2).

sqrt((4 - eps_alpha) / 3) for spur gears, sqrt(1 / eps_alpha) for eps_beta >= 1 and a linear blend of both in between.

Return type:

float

transverse_load_factor_contact(transmission)

Transverse load factor for contact stress K_H_alpha.

Return type:

float

transverse_load_factor_root(transmission)

Transverse load factor for tooth-root stress K_F_alpha.

Return type:

float

load_factors(transmission)

Compute every ISO 6336-1 load factor of transmission in one call.

Return type:

LoadFactors