Dynamic factor

Symbol Kv
Unit -
Attribute-ID dynamic factor
Numeric ID 1013
Value Type PMDouble

The dynamic factor KV considers the effect of internal dynamic forces which are caused by vibrations of the pinion and gear against each other. These forces have an effect on the flank pressure, tooth root stress, and scuffing stress.

KV is defined as the ratio of the maximum force occurring in the engagement of a gear pair to the corresponding tooth force of the same gear pair at a speed approaching 0.

The dynamic factor KV can be calculated/specified in different ways:

Method A

Direct specification of the factor

Method B

When calculating according to this method, the following simplifying assumptions (among others) are made:

  • Every pair of teeth forms a single, elementary mass and spring system
  • An average value for the damping of the gears during mesh
Method C

When calculating according to this method, the following simplifying assumptions (among others) are made:

  • Sub-critical speed range
  • Solid-disc gears of steel
  • Pressure angle α=20°
  • Helix angle ß=20°
  • Total contact ratio εγ=2.5 for helical gears
  • Tooth stiffness c'=14 N/mm/µm, cy=20 N/mm/µm (spur gears)
  • Tooth stiffness c'=13,1 N/mm/µm, c=18,7 N/mm/µm (helical gears)
  • Tip relief ca and cay (inlet)=0 µm

For assumed values for deviations, see DIN 3990 Part 1