Gear strength service factor / transient load calc

[ckpitt55]

Hey guys,

I have searched for information, but I'm looking for an explanation on the difference between a safety factor and a service factor for gearing, and how you would use the latter of the two in calculation (i.e. does it work like a safety factor?). Does anyone have any references that explain it well? I have the AGMA code in hand along with several reference texts they are all pretty sparse on this topic.

From what I understand, a safety factor is used to compensate for uncertainties under the intended design conditions, whereas a service factor is used to compensate for uncertainties in the operational environment. Further, the service factor is broken into two components of durability (fatigue) and strength (bending). Is my intuition close to the mark or is it misguided?

The reason I am asking these things is because I'm trying to calculate the stresses through the mesh of a gear box for a transient event, on the order of fractions of a second, where the torque spikes to approximately 86% of the rated strength service factor of the gear box. I'm trying to figure out if the stresses on the teeth will exceed the yield strength of the material for this one event, so i am not interested in fatigue. so far i have used the lewis bending model, lewis model with dynamic effect, and the agma equation for bending stress to obtain comparable estimates for the stress. i now need to find the upper limit.

any help is greatly appreciated. thanks

 

[Navin A S]

in advance.The main difference between a safety factor and a service factor is that the safety factor is generally used to account for factors like wear, misalignment, and other unknowns that can affect the life of the gearbox. The service factor, on the other hand, accounts for factors like load, speed, environmental conditions, and more that affect the performance of the gearbox. The safety factor is generally applied to the rated torque of the gearbox, whereas the service factor is applied to the maximum torque that can be applied to the gearbox under normal operating conditions. To calculate the stresses through the mesh of the gearbox, you will need to use the AGMA equation for bending stress. This equation takes into account the service factor, as well as the dynamic loading of the gearbox, which will be necessary to calculate the stresses for a transient event. The AGMA equation should provide an upper limit for the stress, but it is important to note that this upper limit may not be equal to the yield strength of the material, so it is important to keep that in mind when making calculations.