Spring without fatigue data

[Verkstad]

Hi

I am looking at a spring from a spring manufacturer with very high compression force 20000 N diameter 32 length 50 see link below. Have hard to find a spring that can handle that high load elsewhere.

But the manufacturer do not have any fatigue data. When i spoke to a reseller he claimed there are no fatigue below 1000 cycles.

For my application that would work since i have few cycles and after some year i can replace the spring.

Can i trust that there are no fatigue below 1000 cycles? I will install the spring according to manufacture recommendation, and max load will be less the 75% of the max load.

Kindly
Paul

https://www.specialsprings.com//en/...-die-springs-iso-10243-2010/products/w-series

 

[MotorCity]

1000 cycles sounds safe for a fatigue threshold. We usually use 10,000 cycles. The only time I would question the number of cycles for fatigue is when looking at how heavily will it be loaded. For example, are the 1000 cycles loading the spring to 5% of its capacity or 95% of its capacity? At 75%, I'd say you're good.

 

[EdStainless]

There are lots of sources out there for similar die springs.
We had them in die sets that cycled every 2sec, for weeks on end.
If this spring won't handle 75% load for a million cycles then someone screwed up the design.
The lack of fatigue data is pure BS.
I recall spring mfg that would give you a mean life curve and a min life curve (mean - 3SD) vs load.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Verkstad]

Thx for the info, sounds good. The load will be less then 75%.

 

[rb1957]

why not run a fatigue test ? 10,000 cycles at 0%-75% cycle.

is this compression-compression cycle, or compression-tension ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[3DDave]

Below some arbitrary number of cycles it's not considered traditional fatigue. When one flexes a paperclip and it fails in 5 cycles that is called "low cycle fatigue" caused by plastic deformation on each cycle. Presumably your spring isn't working above the elastic limit and won't experience low cycle fatigue. In high cycle fatigue there isn't plastic deformation until the section is significantly compromised and there is a rapid low cycle fatigue or simply sudden rupture.

The transition from low to high cycle fatigue at which plastic deformation isn't noticeable is not well characterized so determining that cut-off cycle count is also not well characterized.