Asingle tooth bending (STB) test procedure has been developed to optimally map the AgustaWestland gear
design parameters and a test program on case carburized, aerospace standard gears, has been conceived
and performed in orderto appreciate the influence ofvarious technological parameters on fatigue resistance,
and to draw the curve shape up to the gigacycle region.
In afirstphase, testsupto1 0million cycleshavebeen performed on fourtestgroupsdiffering bymaterial (VAR
and VIM–VAR 931 0, and VIM–VAR EX–53) and by manufacturing process (ground fillet versus unground
fillet); in the second phase, VIM–VAR 931 0 ground fillet specimen have been tested up to 1 00 million cycles.
All the gear types were shotpeened.
FEM analysis, strain gauge measurements and rating formula of AGMA standard are used to express test
loads in terms of tooth root stresses.
The program has been completed by failure analysis, based on SEM, on failed specimens and by ultimate
load tests.