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Up Topic Welding Industry / Technical Discussions / VIBRATORY STRESS RELIEF
- - By SOLDADOR Date 10-06-2004 22:55
I HAVE SOME LARGE FABRICATED MANIFOLDS (800 LBS), A105 MATERIAL, THAT WERE WELDED UP AND THEN FINISH MACHINED WITHOUT STRESS RELIEF. THERE ARE ABOUT 12-15 WELDS ON EACH MANIFOLD; 5-1/2" O.D. PIPE WITH 3/4" WALL THICKNESS. THE ASSEMBLY SHOULD HAVE BEEN STRESS-RELIEVED PRIOR TO FINISH MACHINING. THE ASSEMBLY NEEDS TO BE STRESS-RELIEVED AND I'M QUITE SURE THAT THERMAL STRESS RELIEF WILL WRECK THE FINISHED DIMENSIONS. I WAS TOLD THAT VIBRATORY STRESS RELIEF WILL NOT CAUSE MOVEMENT OF THE COMPONENTS. IS THIS TRUE??? IT DOESN'T MAKE SENSE TO ME...........
Parent - By andy (**) Date 10-07-2004 08:19
I don't have any specific experience with this so I can't answer your question directly. I can point you to some discussions on vibratory stress relief on the web:

http://www.eng-tips.com/viewthread.cfm?qid=92768

http://www.eng-tips.com/viewthread.cfm?qid=77148

http://www.eng-tips.com/viewthread.cfm?qid=61212

these might help explain the process and give some contacts for further information.


Andy
Parent - By RonG (****) Date 10-07-2004 12:00
I got cought in a similar situation a month ago with a very large fabrication (roughly #6000+ all A36 plate) that got to far behind to do PWHT and make delivery. We opted for vibratory stress relief. Our biggest concern was final machining.

I can tell you that for us it worked well enough to hold tolerance and not move during final machining.
Parent - - By thirdeye (***) Date 10-07-2004 12:06
Here is a link to a short article describing one brand of equipment.

http://www.mmsonline.com/articles/0501rt3.html

I have been on repair projects for heavy mining equipment where vibratory stress relief was used during crack repair welding. It was explained as a "conditioning process". BTW, many of the materials on this type of equipment are T-1 and traditional stress relief is not recommended.
Parent - By jon20013 (*****) Date 10-07-2004 12:14
I studied this technology many years ago, and have always wondered why it hasn't caught on within industry as an application? Since I have never personally used it, I cannot say for sure whether it works or not although there seems no shortage of testimonials.

One thing I do wonder though; for those of us who use strictly ASME IX for procedure qualification how does this fit in with the essential variables, I don't recall ASME IX ever acknowledging VSR.
Parent - - By GRoberts (***) Date 10-07-2004 14:42
The first thing you want to consider before looking at VSR, is what is the purpose of your stress relief in the first place. If you need it to improve the performance of the manifold by reducing that hardness of the weld/HAZ, and prevent cracking during service, then VSR will not accomplish this. It is also not a replacement for thermal stress relief (TSR) if it is specified by the code. As mentioned by Jon, it is not addressed by ASME, so it is not allowed to be substituted. However, since it is not addressed, then VSR is not prohibited by the code either, but it can't take the place of TSR.

The second thing you want to look at would be whether it would accomplish what you are looking for dimensionally. Even for VSR, it is normally applied before machining so that it will not move during machining. I do not know if there is any post-machining dimensional data regarding VSR, but a manufacturer of the equipment would be the most likely place to find the data if you can believe them. I have seen some pretty fishy looking data in claims from VSR equipment manufacturers, but hopefully there are some honest ones out there too.
Parent - By RonG (****) Date 10-07-2004 16:11
Very well put! I failed to mention the reason we opted for VSR was the fact we were not concerned with the HAZ just residual stresses.
Parent - - By G.S.Crisi (****) Date 10-07-2004 19:30
Last month (September 2004) I presented a paper before the 30th Brazilian Welding Conference, organized by the Brazilian Welding Association, speaking of Vibrational Stress Relieve.
In English, the paper's title is "Stress relief of welds by heat treatment and vibration: a comparison between the two methods".
The paper has been translated into English by Messrs. Browne Dreyfus International Ltd., of New York City. If you'd like to have a copy, get in touch with Mr. Daniel Torres of Bowne Dreyfus at phone number (212) 867-7700 ext. 18 or dtorres@bdi-ltd.com
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - By TimGary (****) Date 10-07-2004 19:47
Thank you Professor Crisi!
Mr. Torres was very helpful and is sending me a copy.

Respectfully,
Tim Gary
Parent - - By Bonniweldor (**) Date 10-10-2004 04:11
It is interesting to wonder if VSR could be used for residual stress relief of cold formed stainless steel vessel heads. There is no HAZ in this context and the removal of residual stress is paramount for corrosive service as may cause stress corrosion cracking. This would be a classic test of the efficacy of VSR: Form the SSt head and compare SCC response vs. TSR (with untreated formed head as control). To date, I've not noticed any peer reviewed basic research of this sort toward justifying the effectiveness of VSR.
Parent - - By G.S.Crisi (****) Date 10-13-2004 20:49
English being not my mother language, I don't know what SCC and TSR mean. Does the latter mean perhaps Thermal Stress Relief?
Giovanni S. Crisi
Parent - By RonG (****) Date 10-14-2004 11:34
Yes to TSR and "Stress Corrosion Cracking" for SCC.
Parent - - By G.S.Crisi (****) Date 02-23-2006 20:04
Bonniweldor,
I'm glad to announce you and all the frequentors of this site that, based on your suggestion, I've started a research here at Mackenzie University.

The research consists of the following:
1. Make two 304 stainless steel dished vessel heads by cold forming. One of the head is 600 mm (roughly 24 inches) diameter and the other is 300 mm (roughly 12 inches) diameter. Both are 1/4 inch thick.
2. Measure the Brinell hardness on the knuckle of both heads, which is the most stressed part.
3. Measure the residual stress on the knuckle by means of X-ray difractometry.
4. Perform the VSR (vibration stress relief) on both heads.
5. Measure again the Brinell hardness and residual stress by X-ray.
6. Compare the readings and take the pertinent conclusions.

Steps 1 and 2 have been already completed. After the research is over, it's my intention to publish its results on a technical magazine or in a paper before a technical conference.
I'll keep you aware of how things are going.
Giovanni S. Crisi

Parent - - By 803056 (*****) Date 02-24-2006 03:13
That sounds like an interesting research project.

We've considered using VSR, but couldn't come up with any information of how the process works, other than "trust us, it works".

I'ld be interested in what you find.

Best regards - Al
Parent - - By bklauba (*) Date 03-20-2006 19:13
You can see an abstract of a paper on vibratory stress relief at: http://asm.confex.com/asm/tw2005/techprogram/paper_6044.htm

and the full paper at: http://www.msnusers.com/VSRUsersResearch

The paper contains both a review of several worthy papers into this field, plus a list of references, along with case histories and the results of a survey of 20 users of vibratory stress relief.

Also in the paper is an explanation of why resonance peaks shift during effective VSR Treatment; peak growth is relatively well understood, but peak shifting has not been explained well, up to this point.

Parent - - By bklauba (*) Date 03-21-2006 16:45
If anyone wishes to be sent a copy of the paper (which will be published by the ASM within the next 60 days), please email me at: bklauba@airmatic.com

Bruce Klauba
Parent - By bklauba (*) Date 04-20-2006 18:02 Edited 07-13-2007 15:45
A new website that might be of interest:

http://vsrtechnology.net

BK
Parent - - By Bonniweldor (**) Date 04-26-2006 02:35
GCrisi

If it suits you, please post your findings as they become avialable.

Thanks.
Parent - - By G.S.Crisi (****) Date 04-26-2006 14:56
Of course I will. You see, Bonnieweldor, this is an University research and it it progress much slower than a private industry one.
We depend heavily on industry collaboration, which has never been denied, but you've got to fit into their schedules and this means that you have to wait until they have a place for you.
Examples:
The stainless steel plates were donated by a stainless steel company.
The dished ends were made by a local fabricator.
The hardness measurement was done here at Mackenzie's metallurgical lab.
The residual stress measurement will be done in the next fews days at the Daimer Chrysler factory near Sao Paulo.
An so on.
Giovanni S. Crisi
Parent - - By jon20013 (*****) Date 06-05-2006 17:41
I know this Subject Line has been out of ciculation for some time so please forgive me reintroducing it with some questions:

I am interested in using vibratory weld conditioning in my shop for a number of reasons but have some concern over the manufacturers claim of "improved" mechanicals of the weldments.

The Company literature for this equipment makes claims that their process dramatically improves weld joint tensile strength, ductility and also impacts.  I'm not asking whether these claims have merit, but am instead concerned, from a design aspect, whether these alleged "improvements" in weld metal are beneficial to the design of weldments?

I know many discussions have been held on "over-strength" welds, so while I am definitely interested in exploring this technology within my own shop, I remain a little skeptical with regard to mechanical "improvements" of welds which the manufacturer claims. 

I guess what I am really asking is this: are weldments which are claimed to exhibit 92% greater tensile strength, 307% greater ductility and 77% higher impacts than the original design necessarily a good thing?
Parent - By G.S.Crisi (****) Date 06-06-2006 21:48
jon,
in the best case, vibratory stress relief restores the original properties of the base metal, it doesn't improve them. So, the claims that it will improve tensile, impact and ductility by such great percentages are exaggerated, to say the least.
The great advantage of vibratory stress relief is the dimensional stability of the welded piece, i.e., it doesn't change the dimensions and shape of the welded piece, which in certain cases is very important. It also takes less time to get done.
Giovanni S. Crisi
Parent - - By Chris Fischer (*) Date 08-03-2006 16:02
Jon,
You should be sceptical of any exaggerated claims offering such huge changes in mechanical properties. The vibratory stress relief main purpose is to reduce peak residual stresses. Weld conditioning as it is called relies upon the aggitation of the filler metal as it is deposited and derives about as much benefit as pulsed arc welding.
And in answer to Bklauba, we have studied the "peak shifting" phenomenon alluded to by manufacturers of vibratory stress relief and found it to be totally a function of vibrator heating which causes a drifting of the force and speed output of the vibrator. This shifting occured with or without a workpiece being treated and was totally reproduceable at will.
Anyone seeking answers to questions regarding to vibratory stress relief should contact Stress Relief Engineering Co. at 949-642-7820, and check out the website at www.stressreliefengr.com .
Parent - By bklauba (*) Date 08-03-2006 21:06 Edited 01-18-2007 19:40
Chris,

Shifting of resonance peaks during vibratory stress relief is caused three different ways:

  1.  As you described, a warm up of a vibrator that is NOT servo controlled, which will cause a drift up in speed with constant voltage input.  This gives the illusion that the peak has shifted, when it has not.  (NOT a true shift, but an anamoly of instrumentation.)

  2.  A growth of the resonance peak, which causes increased loading of the extreme fiber of the workpiece.  Although a weak response (a doubling of the resonance peak will normally cause only a 1 - 2 % drop in the resonance) this can be seen with the right instrumentation.  Scanning thru the speed range SLOWLY is a must (like 10 RPM/sec) and plotting the acceleration vs. RPM (from a tach, not back-emf of the motor.)  This phenomenon was reported in a paper published by the ASM, that has been posted at:

http://www.msnusers.com/VSRUsersResearch/Documents/ASM%2004%2D2005%2Epdf

The equipment used to make the series of charts at the end of the paper had a resolution of + / - 0.03% vibrator speed regulation, and the vibrator's unbalance was adjustable over a 20:1 range.  If the equipment you try to see effect with only has 2 - 5% regulation, which is what you would expect from a DC vibrator controlled with only a Variac (variable transformer), then you wouldn't see this effect.   [I don't care whether you used AC or DC, (although we much prefer brushless DC, best of both worlds, tight servo, no brushes or commuator to arc, wear out, fail, cause drag, generate carbon dust, etc., etc.), but the vibration data will be FAR MORE DETAILED, if you servo control the vibrator.  Metal structures have resonances that are often amazingly strong, but very narrow, i.e., they have high mechanical Q's.)

  3.  A change in shape of the workpiece, which does occur at times. 

We have used vibration tables that show both responses 2 and 3, but the resonance of the table, not likely to be assocated with any residual stresses, remains exactly the same.  (I will try to post a chart showing this on the msn/VSRUsers site, for your viewing, and will post the link here.)

By using very tightly controlled vibration in the range of 0.03%, with the ability to vary the unbalance over a wide range (20:1), and going to much higher speeds (8KRPM) as opposed  to 3.4 KRPM and having a much stiffer vibrator mounting system and the ability to re-orient the vibrator without having to use an angle plate, we have pushed the envelope.   We can now distinguish between an old casting (whose resonance pattern does not change) and a "green" one, with this technology.  We also can evaluate whether it would be benefical to stress relieve not only before rough machining, but also afterwards. 

You can see more at our website:  http://vsrtechnology.net

Bruce Klauba
Parent - - By jon20013 (*****) Date 06-05-2006 18:31
Professor Crisi;

I'm wondering how your research is coming on this matter?  Would you be so kind as to share a copy of your results when published?
Parent - - By G.S.Crisi (****) Date 06-06-2006 00:06
jon,
take a look at the answer I've posted right up there to Bonnieweldor's comment.
In this moment, vibratory stress relief was carried out at a platework shop located some 100 miles from Sao Paulo.
Next steps will be to measure the residual stress and hardness "after stress relief", to be compared to those that were made "before".
Giovanni S. Crisi
P.S. In this moment I'm in a hurry and can not answer the doubts you raised. I'll do it in a couple of hours.
Parent - - By bklauba (*) Date 01-18-2007 14:12
A new website includes an On-Line VSR Research Library:

  http://vsrtechnology.net

BK
Parent - By sunn625 (*) Date 06-26-2008 08:10
we develop a new vibratory stress relief system with frequency spectrum analysis. It is not resticited to the resonance frequency of the work piece.covering application  from 23% to 100%.
My Email:sunnn@semboo.com

If any query, Pls feel free to contact me
Parent - By sunn625 (*) Date 06-26-2008 08:40
Yes, It is a mechanical vibration energy to redistribute interal stress, to reach to reduce or homogenize the residual stress. after VSR, The tensile strength 、yield strength、hardness are obviously increased

my contact Email:sunnn@semboo.com
Parent - By sinousm Date 07-24-2008 09:16
It is not resticited to the resonance frequency of the work piece.covering application  from 23% to 100%.
u can visit http://www.zdsx.org
Parent - By sunn625 (*) Date 11-19-2009 07:01
If to solve the deformation by vibratory stress relief, you can check the effect as follows:

Select same workpiece, do natural stress relief, thermal stress relief, and vibratory stress relief, and know of the technical requirement. then you can detect the effect of vibratory stress relief. more info, you can visit:http://www.semboo.com/en/index.html
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