What is AGMA allowable stress?

[jackboot]

Please educate me on this subject:

Gear calculations typically use only allowable stress and hardness to calculate power ratings and gear life. These values are listed by the AGMA number like A1 or A5.

Designing a set of gears I only have mechanical information for a specific type of Alloy- tensile and yield strengths.

SO:
What is the allowable stress? -I know this is listed by AGMA and modified by operating factors, but how is it calculated to start with? I only have tensile and yield strength to start with for the particular alloy I have selected.

Is the allowable stress the same as the endurance limit (fatigue strength) of the particular alloy?

Is there a cross-reference for the AGMA numbering system to AISI?

Anyone know?

jackboot

 

[SAP]

Jackboot,
The AGMA allowable stress are determined by laboratory tests and accumulated field experience. It is not just the yield and tensile strength that determines the allowable stress, but other factors such as cleanliness, heat treatment, level o finspection etc. If you know the tensile properties, you should also know the hardness, or be able to measure it, and then slot it into one of the categories in listed in AGMA.

Good luck.
SAP

 

[diamondjim]

Good question and good reply earlier.
You have two things to consider.
First the static allowable stress may be very
high in the magnitude of 57% of the Tensile Stress.
Dynamically, it is less than the above and dependent
on the number of cycles that you are shooting for.
Typically static values for:
shock would be about 50 percent of Tensile
normal would be about 25 percent of Tensile
starting would be about 40 percent of Tensile
I hope this helps.
Contact stresses can be very high, like three
times the tensile depending on the material.

 

[jackboot]

Thank-you both very much.

jackboot