Abstract
Fatigue failure of synchronous belts is investigated under fluctuating torque conditions because the driving torque fluctuates in the automotive engine camshaft drive-systems. Two modes of fatigue failure are observed. The first mode is debonding along the interfaces between stranded glass filaments in cords. The initiation of the debonding is explained by the cyclic bending deformation when the belt is wound around pulleys and transmits the power. A simplified mechanical model is proposed to explain the failure mechanism. The second mode is tooth root cracking on the opposite side of the working flank. The shearing stress at the tooth root is discussed caring out the finite element analysis.
