GB/T 3480.3-2021 Calculation of load capacity of spur and helical gears—Part 3:Calculation of tooth bending strength

Scope

This part of GB/T 3480 specifies the basic formulas for calculating the bending stress of involute cylindrical gears with a certain rim thickness (outer gear SR > 0.5 ht and inner gear SR > 1.75 mn). This part takes into account all factors that can quantitatively evaluate the root stress caused by the loads transmitted by the gears. In practice, the inner gear may exhibit failure forms different from bending fatigue, such as cracks starting from the root circle and extending radially outward. The calculation results of this part cannot ensure an adequate safety assessment for failure forms other than bending fatigue.
This part includes experimental tests and theoretical research conducted by Hirt[11], Strasser[14], and Brossmann[10]. The calculation results are consistent with other methods (references [5], [6], [7], and [12]). The formulas given in this part are applicable to cylindrical gear profiles machined by basic gear-type tools in accordance with GB/T 1356, and can also be used for profiles with an equivalent gear face coincidence degree εαn less than 2.5 and that are conjugate with other basic gears.
The bearing capacity obtained based on the allowable bending stress is called "gear bending strength". This calculation method of the strength is consistent with the results of other similar methods, as described in the "Scope" section of ISO 63361.
If this part is not applicable, refer to Chapter 4 of ISO 63361:2019.

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