Vibratory Stress Relief

OK, Everyone have a good laugh.

Now you've calmed down:

Does anyone have experience of this process either during or post-welding?

I've recently come accross equipment for relief of weld stress in large structures and am interesed in importing them into Aus for local large fabrication projects. The manufacturers I've come across are Meta-Lax, and VSR Technologies.

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We used it for a while. Then the machine broke and we didn't have budget to replace it or get it fixed.

It is not a substitute for thermal stress relief!!!!! It won't satisfy the need to use thermal stress relief for improving fatigue resistance (to my knowlege) nor will it substitue for thermal stress relieve to knock down heat affected zone hardness in alloy steels.

What it might do for you is to minimize the part "walking" during a machining operation. We welded up a cylinder and cut it in thirds. One we thermally stress relieved, one we vibratory stress relieved and one we did nothing.

We machined the ID's to a "finish" dimension and then the OD's. Then we measured the change to the ID's. IIRC the untreated cylinder was 0.010 out. thermally treated was 0.003 out and the vibratory cylinder was 0.006 pi

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John Gullotti

Yeah we tried it. We used it for a while in our machine shop until the unit broke and we didn't have the budget to replace or repair it. That was at least ten years ago.

It is not a substitute for thermal stress relieve to improve fatigue resistance, nor is it suitable for knocking down peak hardness in alloy steel heat affected zones. It's only marginally effective in stabilizing weldments prior to final machining. To my knowlege, no codes describe its use as a requirement or as a substitute for thermal stress relief. You need to search your codes to see if it's prohibited.

The process is heavily touted with plenty of "satisfied customers" and lots of testimonial evidence. At least that's the way it was fifteen years ago. I'm still watiting for a PHD thesis proving the metallurgical distribution of dislocations coupled with rigorous residual stress measurements and studies that use rigorous fatigue and fracture mechanics data to prove the process has a metallurgical benefit. Our chief metallurgist at the time labeled it as "psychological stress relief".

We did a one time test by welding a steel cylinder (I think it was somewhere around 30 inches in diameter and three quarters inch thick) and cutting it into three pieces about a foot long. One we thermally stress relieved. One we vibratory stress relieved and the third was as-welded. We machined the ID's to a "final dimension" then machined the OD's. IIRC, the untreated cylinder went out of tolerance 0.010 inch, the thermally stress relieved cylinder went out 0.003 inch and the vibratory stress relieved cylinder went out of tolerance about 0.006 inch or so. (We didn't do a full statistical evaluation. This was a one time, one data point cheap and dirty test.) In other words, it's better than nothing, and not quite as good as thermal stress relief in helping to maintain tolerances in a machine shop operation. You'd have to know what kind of tolerances to which you're working and understand what it takes to meet them. But if you need to work to tight tolerances, there's no substitute for thermal stress relief if you can use it, or "sneaking up" on the final dimensions with a combination of rough and final cuts using appropriate tooling consistent with your need to control your processing. I'm pretty sure we continued to use our standard machining techniques even with the vibratory stress relief being done on the parts. So, it didn't really save us anything. Thus, when the machine broke, there was no incentive to get it fixed.

Reply to
John Gullotti

I know of companies that machine components within + / - 0.002 - 0.009 range, held over 30 to 60 feet, using the VSR Process. Please be aware that there are several requirements to make a vibratory stress relief system high performance:

  1. Wide vibrator speed range (beyond 6 KRPM) 2. Tight vibrator speed regulation (lower than 0.3 %) 3. Adjustable unbalance, up to and including 2 - 4 in-lbs. 4. Ability to orient the vibrator relative to the workpiece so that it can drive the part effectively into resonance. The aforementioned cylinder should have the axis of rotation of the vibrator (AOR) aligned with the cylinder's axis for one treatment, and perpendicular for a second, since there are two families of resonances that rings and cylinders display (bend and torsional in one group, "egging" or ellipitical in the other), that one orientation cannot excite. See
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    5. Easy to use instrumentation that displays accurate resonance patterns, so that the change that takes during stress relief can be monitored and documented.

If you are short of these performance aspects, so will your results be short of what can be done.

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