Unformatted text preview: The velocity factor K v represents stress augmentation due to mislocation of tooth proﬁles along the pitch surface and the resulting “falling” of teeth into engagement. Equation (5-67) shows that the induced bending moment in a cantilever (tooth) varies directly with √ E of the tooth material. If only the material varies (cast iron vs. steel) in the same geometry, I is the same. From the Lewis equation of Section 14-1, σ = M I / c = K v W t P FY We expect the ratio σ CI /σ steel to be σ CI σ steel = ( K v ) CI ( K v ) steel = ± E CI E steel In the case of ASTM class 30, from Table A-24( a ) ( E CI ) a v = (13 + 16 . 2) / 2 = 14 . 7 kpsi Then ( K v ) CI = ² 14 . 7 30 ( K v ) steel = . 7( K v ) steel...
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