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3 stage reduction Gearbox analysis

- May 24, 2020 at 3:19 pm
  
  siddharthdeshmukh
  Subscriber
  
  Hii, I would ask the seniors to kindly please help me on this topic as i am really out of options.
  
  Well my case is that I am doing the analysis of a reduction Gearbox with three gears.
  
  Mainly im facing two problems here.
  
  1. By hand calculations , i have the values of moment and force acting upon every gear. So i started doing individual analysis of every gear by fixing the centre and applying force along the pressure line on the face of the tooth of the gear and i got satisfactory results but when i combined the three gears and fixed the last one and applied the force on the first, i have very poor fatigue life.
  
  2. The main reason for this post was understanding the contact method selection, I selected the no separation method but it really doesnt work as i thought and just pulls the face along with it. When I selected the frictionless method, the tooth just penetrates the target tooth.Please throw some light on the precise contact method.
  
  I am attaching the wb file also. I would request the seniors here to please help me out as I am pretty much out of options and cannot find any source of authentic info on this topic.
  
  PS- ignore the typos
- May 24, 2020 at 7:54 pm
  
  peteroznewman
  Subscriber
  
  Here is a list of posts on gear teeth.
  
  Use Frictional Contact. Some of those posts mention what is required to have the contact work properly.
- May 24, 2020 at 7:59 pm
  
  siddharthdeshmukh
  Subscriber
  
  Thanks peter for your reply, I was waiting eagerly for you reply. I wanted to ask what would be the precise method for gear analysis.
  
  For example, in my case, the final gear would not move until a moment of 300Nm is generated by it due to frictional resistance by tyres, So I am proceeding by finding the corresponding moment to be applied on the first gear and fixing the third gear. Is this approach correct because I am getting very poor FOS as opposed to the hand calculaions.
- May 24, 2020 at 8:18 pm
  
  peteroznewman
  Subscriber
  
  Your mesh is too coarse to get useful data from it. Read the many posts and you will see.
- May 25, 2020 at 6:50 am
  
  siddharthdeshmukh
  Subscriber
  
  Yes what u say is true, to reduce processing times, I meshed with a body size of 2mm but I'll improve it now.
  
  Also I tried using frictional contact but I cant get around the penetration problem. I read some of your posts on it and tried turning on large deflections and turning off the trim contacts options, but still there is large penetration between the two. Is there any other way of solving this?
  
  Forgive me for asking basic questions because I'm new at this.
- May 25, 2020 at 11:48 am
  
  peteroznewman
  Subscriber
  
  Did you turn on Auto Time Stepping? Did you use a high number for Initial Substeps? Did you increase the Normal Contact Stiffness Factor?
- May 25, 2020 at 2:34 pm
  
  siddharthdeshmukh
  Subscriber
  
  I'm really new to this and havent really did what you said above. If you dont mind can you please be a little more specific on what i should do exactly?
  
  Like i know where all the options you said are and how to use them but how high a number should I use for Initial substeps or How much should I increase the stiffness factor?
  
  Thanks in advance for all the replies.
- May 25, 2020 at 3:55 pm
  
  peteroznewman
  Subscriber
  
  Try to use 100 for initial substeps and try 10 for the stiffness factor.
  
  Before you do that, look at the last results. On the Results Tab, make sure the display scale factor is set to 1.0 (True Scale). If it was set to 2.5e+3 (Auto Scale) or some such number, then the deformations displayed are exaggerated by a factor of 2500 so that might be what you are seeing.
- May 28, 2020 at 6:00 pm
  
  siddharthdeshmukh
  Subscriber
  
  Sorry for late reply.
  
  I did as u said peter but the reults I got were pretty wierd. There was no deformation, no stress and FOS was 15 all over the geometry. It was as if the geometry was highly strong which I know it isn't. i'm attaching the results from the analysis, Please help me out with this.
  
  The iniitial conditions which is used were frictional contact method, revolute joint on the pinion and fixed joint on the gear. I inserted a joint load as moment of 30KNm.

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