• gear
• helical gear
• modification
• transmission
• transmission error

Gears are key-components of any mechanical systems containing transmissions and drivelines. Widely used in industrial applications, their range of application goes beyond automotive, marine and aerospace industry.
The dynamic behavior of gears in operating conditions is usually complex and difficult to model in an exact way. The reliability of gear transmission systems depends on the accuracy and robustness of the modeling techniques. With the advent of high performance computing, the gear dynamics can be simulated in the design process, in order to optimize the performance and efficiency of power transmissions. The evaluation of mechanical transmission dynamics is a prerequisite for ensuring good noise, vibration (N&V) and durability behavior.
Gear Transmission Error (TE) is widely recognized as the main internal source of vibration in power transmissions. It quantifies the deviations from a perfectly kinematic motion transmission which in a real case are introduced by deflections, misalignments and manufacturing errors. The TE can be directly linked to durability, noise and diagnostics assessment.

Measurement procedures have been established to generate repeatable data acquisition from the test rig. Multiple gear have been evaluated using the test rig.
High precision sensors have been deployed to ensure the quality of the acquired data. TE measurement proves to be repeatable with tight confidence bounds. The raw data has been post-processed using frequency/order analysis. The spectral analysis reveals the run-out and tooth-passing components. The peak-to-peak values of TE (tooth-passing component) vary with the applied torque and the shape of the TE signal loses smoothness.
Numerical multibody model has been used to simulate similar test condition and to better understand the gear meshing under misalignment.
This thesis shows that in gears with angular misalignments between shaft and gear, a major improvement on transmission error is obtainable by the application of microgeometry flankline parabolic crowning modification.
The comparison of the analysis cases in the simulations shows a good agreement between the numerical and the experimental results.