Problem for modeling the contacts between the teeth of two helical gears

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  • Last Post 29 March 2019
LF2019 posted this 11 March 2019

Hi everybody

I want to investigate how the contact stresses in the teeth of two helical gears are changed by time. The gears are shown below. The lower shaft is rotating at 6000 rpm and a moment (4000 N.m) is applied to another shaft. Contact and target surfaces are also defined, however, the results are very weird, not only there is not any contact between the gears, the larger gear is massively expanded! I have sent some pictures that show the details of the modeling. I will appreciate if you help me to solve this problem.

Regards

 

 

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mrife posted this 11 March 2019

Hi LF2019

The phrase "larger gear is massively expanded" - does the large gear expand radially?  If so this sounds like a classic issue of trying to represent a finite deflection/rotation with an small (infinitesimal) deflection/rotation theory.  Try turning Large Deformation 'On' in the Analysis Settings.  And set some reasonable time or sub steps.  

 

Mike

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LF2019 posted this 12 March 2019

Hi,

Thanks for your answer. Large deflection is ON by default, however, I only use 1 sub step. So, I should run it again with more sub steps to see what happens. 

Regards

  

Tez123 posted this 14 March 2019

Hello LF2019

Reduce the load step make gear to rotate one or two rotation to check contacts are working

In frictional less contact change Behavior to Asymmetric

Trim contact to No

detection method to normal to target

try with this settings and if you see penetration in teeth's. Play with normal stiffness with value 0.1, 5 and change update stiffness to update each interval.

Put screenshot of analysis settings

 

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peteroznewman posted this 14 March 2019

Please show the Analysis Settings Details. You want the Initial and Maximum Time Step values to allow only a small fraction of rotation within one gear tooth contact. You can know this only in relation to the rotational velocity, the diameter of the gear and the number of teeth.

Please show Details on the Displacement. What geometry is that scoped to?

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LF2019 posted this 29 March 2019

Hi,

 

Thanks for your useful comments. Unfortunately, my problem still persists even after doing what you suggested. I have cleared the mesh to reduce the size of the workbench file and then I have uploaded it in Google Drive. I would appreciate if you check the file to find out where I have made a mistake. Based on the rotational velocity of the small gear (6000 rpm), I have evaluated the rotation angles and the time steps. To apply the boundary condition due to the journal and thrust bearings I have used displacement and cylindrical support. A moment has also been applied to the large gear. What I am going to find is the contact pressure during one complete rotation of the small gear, however, here I have only considered 10 degrees rotation of the small gear to check if the simulation is OK, and unfortunately, I have failed.  

 

Thanks for your time and help

 

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