Spring first natural frequency and hysteresis

[UFO]

TL;DR

Coil spring change in first natural frequency, and hysteresis with use and age.

Could anyone help me with some info on compression helical springs. First I would like to know if this type of spring would even have any appreciable histeresis when new, and if so does it does it grow with repeted use and age. I would also like to know if there is any relationship beteen the first natural frequency, and hysteresis, and, or with use and age. Does this type of spring have any change in properties when used hard, in other words does it wear out at all before it reaches its fatigue end of life and breaks, other then a slight bit of yield or sag. I have found conflicting results on this, and the formula for the first natural frequency does not reference any use cycles on the spring.

Thanks for any help

 

[jrmichler]

I have experience with helical steel compression springs in high load, high speed, high cycle usages. I have never seen signs of hysteresis in the spring itself, but we never looked for it either. I have seen wear in spring seats caused by the springs moving under load. That wear would show up as a hysteresis loss.

I have seen yielding in compression springs where the usage was nominally within manufacturers specifications. That turned out to be caused by spring surge at high speed, which caused peak spring stress to exceed the design specification. Since the surge frequency was over 1 kHz, we needed 10,000 frame/second high speed video to see it. This work was in an industrial environment on a product line of high speed paper towel interfolding machines. After we fixed the problems, the springs lasted over a billion cycles without failure.

In earlier work (grad school), I tested over 4000 steel compression springs in high cycle fatigue. Depending on load, some tests went over 20,000,000 cycles. I did not see signs of hysteresis, but did see signs of wear on the spring ends. The machine was designed to test up to 12 springs at a time at 3600 cycles per minute. Citation to the paper: Michler, J.R., Bhonsle, S.R. High-cycle spring fatigue test machine. Exp Tech 17, 17–19 (1993). And a photo of the test machine from that paper: