General Mechanical

General Mechanical

Regarding calculation of fatigue life of gears

    • Nihit Raj
      Subscriber

      Hi there,


      The problem we are stuck in is that we have to calculate the life of a gear for the gearbox of our BAJA vehicle. We tried calculating using the fatigue tool in ANSYS static structural (using revolute joints).
      The significant doubt I have is to which extent the calculated life is correct and whether it takes all mechanical factors into account or not (like the Dynamic Load factor, Reliability factor, Velocity factor, etc that are mentioned in the standard IS-4460 Gear Calculations, I've attached a picture of the list of factors) if not then how to capture these factors while calculating the fatigue life of gears.

      Thanks in advance, I'll be highly obliged for it.

    • Daniel Shaw
      Ansys Employee

      The Mechanical Fatigue Tool (FT) directly uses the Mechanical calculated nodal stresses.  It does not directly do IS0-4460 fatigue calculations. The FT has one general Fatigue Reduction Factor (Kf) that can be used to adjust the calculated stresses to include a reduction in resistance to fatigue damage for conditions such as surface finish.  To include all the factors identified in IS-4460 in the FT calculations, you would need to determine the accumulated effect of all those factors and apply it as Kf.  Also, some of the factors you identified (such as, size factor and endurance limit) are typically included by adjusting the S-N curve rather than the alternating.

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