14.11 Thermal contact coefficient

The thermal contact coefficient BM accounts for the influence of the material properties of pinion and gear:

        ∘---------------
BM1  =   λM1  ⋅ ρM1 ⋅ cM1
        ∘---------------
BM2  =   λM2  ⋅ ρM2 ⋅ cM2

For martensitic steels the range of heat conductivity, λM, is 41 to 52 N/sK and the product of density times the specific heat per unit mass, ρM cM is about 3.8N∕[mm2K], so that the use of the average value B M = 13.6N∕mms0.5K for such steels will not introduce a large error when the thermal contact coefficient is unknown.