Crack Growth in Spiral-Bevel Gears: 3 Generations of Simulations

The following are simulations of crack growth in a spiral bevel pinion tooth of a transmission gear in an OS-58 helicopter. This problem has been attacked in the CFG through 3 generations of simulators, with increasing levels of geometrical and field resolution and boundary condition approximation.

First Generation: Exploratory Studies with a Finite Element Analysis Engine, circa 1999

A relatively coarse finite element model was created which explicitly represented 3 of the 19 pinion teeth. The loading on the tooth was fixed in the middle of the tooth length, parallel to the initial crack, approximately half way up the tooth height. This is a very crude approximation of the moving contact load on the face of the tooth. The movies below are of 4 different views of the same crack propagation. The color contours are of the first principal stress.

To watch the crack grow, click on one of the pictures.
Quicktime movie files are available for downloading after selecting a view.

Full view of solid model	Slice through center of crack
Finite element mesh	View from inside gear

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Second Generation: Detailed Studies with a Boundary Element Analysis Engine, circa 2001 (see Spievak et al.)

A relatively coarse boundary element model was created which explicitly represented 3 of the 19 pinion teeth. The loading on the tooth was an approximation to the actual moving contact patch. This is a much improved approximation of the moving contact load on the face of the tooth. A movie showing cracking in the gear can be downloaded.

Third Generation: Detailed Studies with a Parallel Finite Element Analysis Engine, circa 2004 (see Ural et al.)

A very refined (>1M DOF), parallel finite element model was created which explicitly represented 3 of the 19 pinion teeth. The loading on the tooth was an improved approximation to the actual moving contact patch.  A movie of this simulation is available here - it is about 60MB.