4。15 Comparison of measured mechanical power losses of gear pairs having different surface

treatments at Ω = 6000 rpm 98

A1 Index error measurement 111

A2 Pitch error measurement 112

A3 Tooth spacing error measurement 113

A4 Tooth thickness measurement 114

A5 Measured tooth lead traces 115

A6 Measured tooth profile traces 116

NOMENCLATURE

Symbol

  Definition

rotational speed - disk Units

(rad/s)rotational speed - roller (rad/s)

  normal load (N)

  entraining speed (m/s)

  sliding velocity (m/s)

R slide-to-roll ratio (unitless)

  bearing friction torque (Nm)

  contact friction torque (Nm)

  total traction torque (Nm)

μ friction coefficient (unitless)

σ contact stress (GPa)

λ ratio of minimum film thickness to root- (unitless)

mean-square surface roughness amplitude

h film thickness (μm)

Ω input gear speed (rpm)

  applied torque (Nm)

  reaction gearbox torque loss (Nm)

  test gearbox torque loss (Nm)

T total torque loss (Nm)

  spin power loss

mechanical power loss (kW)

(kW)

P total gearbox power loss (kW)

1。1 Background and Motivation

One class of power losses occurring in drive trains is caused by friction in the lubricated contacts of power train components such as gears and bearings。 Improvements in efficiency through reductions in such losses are achievable through advanced materials and coating technologies while the power density of drive systems and engine cycles can be impacted simultaneously。 As friction induced, load dependent (mechanical) power losses take place at lubricated contact interfaces of such components, the surface roughness characteristics and the elastohydrodynamic lubrication (EHL) conditions of these contact interfaces become the focus of efforts to reduce such power losses。 Numerous commercial engineered surface techniques aimed at reducing the amplitudes of machined contact surfaces as well as removing the directionality of the machining marks have been advocated。 Similarly, a number of surface coating technologies have been claimed to reduce mechanical power losses through their “anti-friction” characteristics。   Yet, there have been only a few studies that compare performance of