For helicopter gears many aspects of design and manufacturingmust be analyzed, such as material cleanliness, case depth andhardness, tooth root shape and roughness, and compressive residualstresses. Moreover, these gears are designed to withstand loads inthe gigacycle field, but are also subjected to short durationoverloads. Therefore a precise knowledge of the shape of the S-Ncurve is of great importance for assessing their in-service life. Asingle tooth bending (STB) test procedure has been developed tooptimally map gear design parameters and a test program on casecarburized, aerospace standard gears has been conceived andperformed in order to appreciate the influence of varioustechnological parameters on fatigue resistance, and to draw thecurve shape up to the gigacycles region. The program has beencompleted by failure analysis on specimens and by static tests.Some accessory investigations, like roughness and micro-hardnessmeasurements, have also been performed. Gigacycle tests confirm theestimations done on the basis of the shorter tests, both in term offatigue limit and of curve shapes.
- Edition:
- 08
- Published:
- 10/01/2008
- Number of Pages:
- 12
- File Size:
- 1 file , 690 KB
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