Plate and Beam composite
Plate and Beam composite
(OP)
I have a sanwhich structure made of two beams inbetweem two flat plates welded. This structure was pressurized and after some time ( 50 PSI) I hear a pop noise..this continued as the pressure was increased upto 300 psi. Then when the pressure on the plate was reduce slowely, still heard a pop noise. Can some one explain what caused this noise? Thanks for any suggestions.
Jag
Jag





RE: Plate and Beam composite
Now a guess on the pops. It may be that the plates have initial out of plane deformations, some of them in the form of depressions toward the interior. Even if the general shape of the edges is quite undeformed, these depressions may turn unto bulging ones when some specific inner pressures are reached. The pops you may be hearing would be then the claps of elastic buckling, not unlike the one we hear when agitating sheets of silverfoil around chocolat.
RE: Plate and Beam composite
Plates were flat before welding. It is possible small deflections after weld. Still, can it act like agitating sheets?Also could this popnoise ( high pitch metal to metal knocking noise)could be due to shear slippage between plate and beam on the unwelded 4 th corner?
Thanks
Jag
RE: Plate and Beam composite
RE: Plate and Beam composite
I am also concerned about the wisdom of applying internal pressure at 300 psi to a structure like this ??
RE: Plate and Beam composite
Consider these things:
In code NBE EA-95 of Spain welding a 1/4 thing to one 1 inch thick is really not allowed since the weld exceeds the maximum for the thinner element and the minimum for the thicker, whichever the way. This is not to say there won't be instances where such problems appear and welds are made but surely other codes are called unto place for justification.
Coundn't be that the strength concentration provoked by the lack of the inner welds in one of the plates has initiated failure, and you have heard two instances of which during inflation? Think for a moment, to the exten it can resist moment, the sole weld will try to fix the plate, and the stress concentration start cracking through the weld or heat affected zone.
RE: Plate and Beam composite
In this case, instead of using a flat plate of 4", this built up structure provides adequate resistance to deflection due to pressure load.
The structure was checked using FEA and shear calculation was carried out to specify the weld thickness. It is interesting to know about Spanish welding code. But I believe weld like that is pretty common. ( for instance in tube to shell weld in a pressure vessel)
RE: Plate and Beam composite
RE: Plate and Beam composite
Thanks a lot for you input. Steel to Steel friction Vs Shear slippage will be my guess too. Anyhow, do you know of any research work / text / code spec to look up more on this topic.
Thanks again
Jag
RE: Plate and Beam composite
http://www.google.com/search?q=Noises+Steel+Structures&hl=es&lr=&ie=UTF-8&oe=UTF-8&start=20&sa=N
There are some promising links.
Also comes to my mind that the tubes will have the corners round. Upon application of pressure this may induce curvature in the webs of your composite structurem this being concomitant to what said.
RE: Plate and Beam composite
Thanks for the info. Carried out a test today and results are quite interesting. Assuming it was metal to metal friction, applied lubricant between the metal and then pressurized. There was no poping sound !! Looks like infact the differential displacement overcomming the friction created the noise.
Wonder anyone did (sureley there should be!!) research on this topic !!
Jag
RE: Plate and Beam composite