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Publication Date: 2017-Feb-08
Document File: 6 page(s) / 178K

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GE Avio S.r.l.: OWNER [+2]


The device described herein is used for speed up single tooth bending gear testing.

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The device described herein is used for speed up single tooth bending gear testing.


In order to determine the absolute gear strength allowable values, and not only relative

comparison of materials strength, accurate single-tooth bending tests have to be performed. It

translates to the following concepts: a) deterministic knowledge of the stress on the gear tooth

and b) repeatability of the test.

In gear testing machines, for Single Tooth Bending tests, a device is typically used in a

two phase test process. The first phase includes the test article (i.e., the gear) setup that should

be accurate in order to provide repeatable testing conditions. The second phase is the actual gear

testing, which works correctly by freeing the gear bore from the above centering.

The stress on a single gear tooth is determined by the angle at which the load is normally

and tangentially applied to the involute profile, and on the magnitude of those loads. The

deterministic knowledge of normal load can be achieved via a load cell and subtraction of the

inertia of the moving anvil. The determination of the pressure angle at which the gear will be

loaded has to be performed accurately. This can be done firstly centering the gear on a known

diameter with very small diametrical clearance (order of magnitude: hundredths of mm), then by

rotating the gear so that the reaction tooth reaches a determined position on a fixed anvil. The

test tooth involute profile will geometrically be located in a position that will depend only by the



tooth to tooth pitch error on the gear. After the positioning phase, the load anvil and/or the

reaction anvil will harmonically oscillate performing the actual fatigue test.

During such a test, the gear will elastically bend itself and the inner bore will deform,

reaching the inner circumference an inward deformed position, The magnitude of the

deformation is order of magnitude of the tens of mm. If a precise pin was present, the gear will

be constrained to move, realizing localized fretting and exchanging pin/gear load in a random

pattern, avoiding the possibility of a deterministic quantification of the load distribution, and

therefore gear stress.

The current art is a fully removable precise pin. On the state of the art, when the gear

tooth is broken (that is the task of test), the gear body will release the elastic energy via its full

body motion, and it should be contained via some elastic string, risking however damage to itself

and to the system.