DIN 3991-3:2024-06

This document specifies the fundamental equations for determining the tooth root load capacity of straight and helical bevel gears, Zerol, spiral bevel and hypoid gears with a minimum material thickness under the tooth root of 3,5 × m_mn and includes all influences on the tooth root strength that result from the load transmitted by the gearbox and can be quantitatively assessed. The equations in this document are based on equivalent cylindrical gears with a contact ratio of ε_va < 2. This document does not apply to tooth root stresses beyond the permissible values for 10³ load cycles, since stresses in this range could exceed the elasticity limit of the tooth. The standard differs from DIN 3991-3:1988-09 as follows: a) the scope has been extended to include offset bevel gears (hypoid gears), for which the calculation method has been revised; b) for the use of material characteristics, this document refers to the more recent ISO 6336-5, which does not preclude the possibility of a later edition referring to a revised DIN 3990-5; c) a spiral angle factor Y_BS has been introduced; d) a load distribution factor Y_LS has been introduced; e) the graphical methods for determining calculation factors have been removed; f) the original method B2 for determining the relative surface factor Y_R-rel-T has been removed; g) the relative support index Y_d-rel-T has been renamed relative notch sensitivity factor. The original method B2 has been removed in the process; h) a life factor Y_NT has been introduced. This document has been prepared by Working Committee NA 060-34-13 AA "Kegelradverzahnungen (SpA ISO/TC 60/SC 2/WG 13)" ("Bevel gears (SpA ISO/TC 60/SC 2/WG 13)") of Section "Gear" at DIN Standards Committee Mechanical Engineering (NAM). Representatives of the manufacturers and users of bevel gears and of the universities contributed to this standard.