Tooth Bending Strain Rate Analysis in a Counter Shaft Drivetrain and Implications on Fatigue Strength

Gears are subject to multiple fatigue failure modes including tooth bending fatigue, tooth flank fracture, and surface rolling fatigue. Engineers are expected to ensure that the gear can survive well into the very high cycle fatigue (VHCF) regime (>107 cycles). With more widespread recognition of subsurface initiated fatigue failures being the driving factor for VHCF failures, demand is increasing for experimental fatigue data in the VHCF regime. This in turn creates a need for high-speed testing methodologies and an understanding of how those results translate to meshing gears. One part of that understanding is the frequency effect which is driven by strain rate dependent plasticity behaviors. This study combs through current literature and provides an analysis on an example countershaft electric vehicle drive unit to explore what potential strain rate dependent effects there might be in gear fatigue failures. Requirements for fatigue testing at matched strain rates are outlined. © 2023 The Authors.