AGMA 90FTM2-1990 pdf free.An Industrial Approach for Load Capacity Calculation of Worm Gears (Verifying and Design) by: Michel Octrue, CETIM.
If the different rating methods usually used for designing worm gears ([11,18] a (101) consider their limited Life because of TEETH BREAKAGE and CONTACT PRESSURES, experience shows that in molt cases, itisthe SURFACE DEGRADATIONS OFTHE WORM WHEEL which limit the gearing life.
The main cause for SURFACE DEGRADATION Is the fatigue phenomenon on the material layer submitted to CONTACT PRESSURES. This has brought us to develop a method of calculation allowing to evaluate the Level and distribution of contact pressures along the flanks of the teeth.
As opposed to existing methods of calculations, the distribution of contact pressures is no longer supposed to be uniform.
The development that follows presents the method basis used as well as a simplified method which can easily be applied industrially either for verifying or design.
2 REMINDER OF ANALYTIC METHOD
For a worm gear, the cartographic calculation of contact pressures is obtained from a detailed analysis of meshing ofa cylindrical wonn with the mating conjugate wormwheel. In fact for this type of gear the gearing conditions evolve continuously and difTer from one point to another in the same contact line; thus the name of analytical method ([21 to (4J).
The analysis of the meshing is performed at 2 steps:
– STEP 1: it aimed to determine tbc a relative position of the worm and the wonnwheeI the instantaneous load distribution along the meshing teeth. This distribution depends on the teeth geometry, the contact geometry and the materials making up the teeth. Ills thus possible to calculate a pressure level for each contact point.
– STEP 2: by varying the relative position of the worm and the wormwheel it is then possible to study the contact pressure fields on the whole contact zone of the gear.
The principle on which is based the analytical rating method rests on determining the contact point for which the contact pressure field attains its maximum. The maximum load capacity admissible by the gear is thus limited by the pressure allowed by the most weaker material (generally that of the wormwhecl) for the mimbcr of request cycles.AGMA 90FTM2 pdf download.