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Joined: Dec 2003
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Hi, new to the forum. Anyway, I'm currently doing a modification on a regular shot peening machine for leaf springs as we want to turn it into a stress peening machine. However, we have very limited (and rather old) documentation and we're faced with a bit of a problem.

When pre-stressing asymetrical leaf springs, should one align the hole of the spring with the middle point of the jig and therefore deflect the eyes at different lengths? or should I just align the eyes on the horizontal plane, forget about the shift in the hole of the leaf and deflect the same length for both sides of the leaf?

We're about to conduct an experiment to asses the difference between the 2 but if anyone has any info it would be greatly appreciated.

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It's not clear from your description what the orientation of the spring would be in the peening machine. Can you send a digital picture? send to [email protected]

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Hi. Thanks for your reply. Unfortunately I haven't been able to get the picture. I was planning on sending you a screen capture of the Solid Edge model. In the mean time I'll try to post a more precise description.

I have an asymmetrical leaf spring with eyes. That mean s that the distance from the bolt hole to the eye in one side is differentr than that to the eye on the other side of the leaf. Now, the rather scarce literature regarding the preload process for stress peening of leaf springs states that one should achieve a uniform stress of 90kg/mm^2 throughout the leaf. Unfortunately this isn't possible. This uniform stress can only be achieved between the support points of the leaf springs (think of a cantilever beam with 2 supports which is loaded at both ends and I'm looking at the moment diagram which relates to the stress of the leaf). Now, if I place the leaf in such a way that the center hole is aligned evenly between both support point I would need to deflect both eyes at different distances in order to achieve the desired stress between both support points (obviously the larger side would need a larger deflection). On the other hand I could place the leaf on the jig in such a way that both eyes are at the same height (prior to the pre-load) and have the same deflection for both eyes. This would mean that the center hole of the leaf wouldn't be aligned evenly between both support points. This would mean that if I stand on the hole of the leaf during the pre-load, the region at the desired stress wouldn't be as long on one side as that of the other side and this would suggest that the compressive stresses due to peening would be different than those expected throughout the length of the spring.

So, my question is, which is the most appropiate way of deflecting asymmetrical leaf springs?

I've seen several pictures of stress peening machines for leaf springs and they all deflect both ends at the same distance. However, there's no information on weather this is the correct way to do it or just the easiest way. And if this was done in this way, is loss of compressive stresses in certain areas because of this arrangement acceptable?

[This message has been edited by jChampaigne (edited December 10, 2003).]

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Click here to see a "sketch" of the stess peening device CHS refers to:


www.shotpeener.com/ubb/leaf_setup.html

[This message has been edited by webmaster (edited December 16, 2003).]


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