Calculation acc. to FVA 240/II with input parameters from FVA 411 (optional)

In the flank fracture calculation according to FVA 240/II, the principal shear stress is set in relation to the core hardness of the gearing. The following methods are available for calculating the principal shear stress:

• Calculation of flank fracture acc. to FVA 240/II:
  • Bevel gears (no axial offset): load capacity calculation according to DIN 3991
  • Hypoids (with axial offset): load capacity calculation according to Niemann/Winter
• Calculation acc. to FVA 240/II with input parameters from FVA 411 (optional):
  • Bevel and hypoid gears: load capacity calculation according to FVA 411

A simple calculation method for estimating the risk of flank fracture for bevel gears was developed in FVA Project 240/II, based on extensive investigations of this type of damage on gears in both test and in practice (R. Annast: Flank load capacity and running behavior of hard-finished bevel gears, damage from flank fracture. FVA publication 690, Frankfurt, 2003).

The key parameter is the ratio of principal shear stress to core hardness: τ_H12 / H_KH [N/mm²/HV].

Design recommendation: $\frac{{\tau }_{H12}}{H_{KH}}\le 0,55 \frac{N}{m{m}^2 HV}$

If the limit value is exceeded, the risk of flank fracture is high. The ratio τ_H12 / H_KH can be influenced by the hardness profile and the core hardness at half of the height of the flank, as well as by the load and the curvature ratios.