AGMA Gear Stress Briefing + Calculations

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J: Bending Strength Geometry Factor

• Accounts for tooth geometry and related stress

• Uses gear teeth #, pinion teeth #, gear vs. pinion, pressure angle coming at tooth tip, correction factor)

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Kv: Dynamic Factor

• Accounts for the vibrational loads created from tooth to tooth impact of gear teeth

• Depends on:

  • Gear Quality Index (Qv)

    • AGMA determined geometric accuracy of teeth (Q3 to Q16, low to high quality)

      • Accounts for:

        • Tooth lead or tooth alignment (difference between the specified lead/helix angle and the actual in spur/helical gearing)

        • Involute profile variation

        • Pitch variation/Spacing variation

        • Radial runout (accuracy in distances from teeth to center of rotation)

  • Pitch line velocity

    • PLV = (pi*pitch diameter*gear speed)/12

• Calculating Kv:

• Instead of calculating the dynamic factor, you could take into account the resulting transmission errors of gear quality Wt (tangential load) and leave dynamic factor as 1

Km: Load Distribution Factor

• Depends on face width of the gear

• Accounts for uneven distribution of Wt to the face width

• Increases with size of face-width

Ka: Application Factor

• Accounts for fluctuating/shock loads on the teeth

• Does not apply in smooth applications (Ka =1)

Ks: Size Factor

• Considers that test samples in fatigue data testing may be smaller than in real life

• AGMA has no value or formula

• Generally, Ks=1 when you limit the maximum allowed stress limit

• Conservative approach: Ks 1.25-1.5

Kb: Rim Thinness Factor

• Gears made on solid disks: Kb=1

• Gears that are very large made on rims and spokes (thin rim to tooth depth)

Ki: Idler Factor

• Idler experiences more cycles of stress per unit of time

• Idler: Ki=1.45

• Non-idler: Ki=1

AGMA Gear Calculator

Source: https://theengineeringblog.com/gear-design-by-agma-theory/