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Allowable stresses of an extension spring, reply

Allowable stresses of an extension spring, reply

Allowable stresses of an extension spring, reply

(OP)
thread404-351326: Allowable stresses of an extension spring

Thank you very much to all by the help.

I just talked to my friend. The springs are working fine today.

I have gotten this information of Carlson, in Springs magazine, courtesy of Spring Manufacturers Institute, confirming your suggestions:

"When to Use:
The stress correction factor to determine the total stress in compression, extension, and torsion springs shoud be used:
1) when a spring is subjected to severe service
2) when a spring is subjected to elevated or below freezing temperatures
3) when a spring is subjected to shock, or rapid deflections over 300 cycles per minute
4) for extremely small spring indexes (D/d such as 3)
5) for checking the fatigue life or endurance limits

When Not to Use:
A large percentage of springs for general use can be designed without including a correction factor. It need not be used:
1) when calculating the solid stress to see if a permanent set may occur (only the torsional stress determines permanent set);
2) when calculating the permissible torsional stress for initial tension in extension springs;
3) when designing seldom used springs and those for light service in bomb fuses, bumpers and shock absorbers; and
4) when springs support static loads, have small deflections, or low stress ranges.

How to Use:
It is best to use the standard spring design formulas for stress and deflection without including the correction factor in the formulas. Then, if service conditions require it, the torsional stress can be multiplied by a correction factor afterward. A determination can be made at that time to see if a desired fatigue life or endurance limit can be met."

RE: Allowable stresses of an extension spring, reply

(OP)
And about this issue, Carlson says:

"SMI recommends a conservative and consistent use of the stress correction factor and advises the use of the Wahl formula"

Jh0an1

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