allowable stress in tension for Vton A 1

[saitools]

I would like to know the allowable stress in tension for Viton A rubber expressed either as Pounds per square inch or elongation %.
Thanks
Saitools

 

[BLN]

Allowable stress? Isn't allowable stress determined by the designer. Shouldn't that be maximum or yield stress? What temperature?

 

[BLN]

You should contact Dupont-Dow for specifics, but what I found was 1600 psi stress and 165% elongation. I assume these are ambient numbers.

 

[saitools]

The designer can design the component only on the basis of the allowable stress for the material.The working stress will be much lower than the yield/max stress .I want to know the safety factor on yield/ Ultimate tensile stress.
All temperatures are ambient.
Thanks
Rajan

 

[BLN]

Had to pull out my statics and strengths of materials book. What I found was
Allowable stress is the yield stress divided by factor of safety (for materials with elongation greater than 5%), with factors of safety range between 1.5 and 4.0.

When I worked on NASA contracts the factor of safety was dictated prior to any design (normally 1.5). I was told by an aircraft engineer their factor of safety for design was 1.25.

If you have test capabilities you may want to run some samples.

 

[saitools]

My understanding is rubber does not have an yield point/it is not reported in standard specs.Can we safely use 1/3 of UTS which is a guaranteed value as Minimum UTS by all rubber manufacturers?
Please advice
Thanks a million
Best regards
Rajan

 

[BLN]

You're right. I've always reported max. stress (ultimate stress) whenever I've tested elastomer samples. The curve (stress/strain or displacement) is linear. 1/3 of the ultimate would probably be a safe bet. I would rather design on the side of safe operation.

 

[BLN]

One other thing, if you have the capability to test the rubber it would be advisable to test a few samples and use the test data to determine ultimate stress. I'm not from Missouri, but I prefer to use test data over vendor's stated values.

 

[saitools]

BLN,
You have been most helpful!
Million thanks.
Best regards,
Rajan