Wh are welds held in Tension even when loded in compression

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Anybody?  Anybody?Birds are singing, crickets are chirping...........Waiting patiently..........Nobody's perfect, I'm a nobody, therefore I am perfect!
Reply:Sorry about the poor spelling on the title.  It isn't my spelling just my typing that sucks!Nobody's perfect, I'm a nobody, therefore I am perfect!
Reply:That could get to be a complicated answer, lol  i have a theory in my mind, but not sure enough about it to help you out.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:All Right...you book learned fancy school boys read us uneducated masses arguing all the time, YOUR TURN !! I've typed my GUESS several times in that little message box but I keep erasing it...lol. Step up to the plate, could be someone might learn from it. I think I understand tension and compression but not how it relates to the weldment itself. STEP ON UPAnything worth doing is worth doing RIGHT
Reply:I would guess that a weld is always in tension because of the shrinkage that occurs when cooling.Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:I smell something funny.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:That is exactly right.  Whenever a weld occurs we add heat to the area, agreed?  Heat causes the metal to expand and then as it cools it contracts, this contraction places the weld in tension.  So if we place a load on the part which places the part in compression the weld is still exerting tension on the surrounding part.Very good answer.  Nobody's perfect, I'm a nobody, therefore I am perfect!
Reply:Originally Posted by zapsterI smell something funny.....zap!
Reply:That was my thought...but it was just a thought.
Reply:Originally Posted by goose-emThat is exactly right.  Whenever a weld occurs we add heat to the area, agreed?  Heat causes the metal to expand and then as it cools it contracts, this contraction places the weld in tension.  So if we place a load on the part which places the part in compression the weld is still exerting tension on the surrounding part.Very good answer.
Reply:I had it explained just like goose-em stated. I was also told that the heating process rearranges the molecules by size distributions smaller ones near the heat. Which if I remember right is part of the reason the weld is stronger than the material but also contributes to the tension. If this doesn't bring the engineers out of the woods nuthin will, have fun I will be lurking.
Reply:Ok, I was thinking along that lines, but Something didn;t seem right.  So anytime you weld a joint it stays in a constant state of tension?  So over time from vibration, fatigue, etc... it doesn't normalize?  Even if you anneal it so to speak the joint will still be in a state of tension? ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Goose-em,OK  Question.  What happens when the welded assembly is "stress relieved"?Is the weld no longer in tension?Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIGoose-em,OK  Question.  What happens when the welded assembly is "stress relieved"?Is the weld no longer in tension?
Reply:Originally Posted by zapsterHowever..We will wait for the "real" answer.....zap!
Reply:Originally Posted by zapsterYou answered your own question...However..We will wait for the "real" answer.....zap!
Reply:I have to stop right here..right now..I came this close to getting banned last night...Count to ten.........zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by olddadI thought the question now was "are they real ? or are they memorex ?"
Reply:123456 ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapster123456 ...zap!
Reply:Originally Posted by SundownIIIQuestion.  What happens when the welded assembly is "stress relieved"?
Reply:Originally Posted by goose-emThat is exactly right.  Whenever a weld occurs we add heat to the area, agreed?  Heat causes the metal to expand and then as it cools it contracts, this contraction places the weld in tension.  So if we place a load on the part which places the part in compression the weld is still exerting tension on the surrounding part...
Reply:Anyone ever heard that old song, "Devil in disguise" or something like that?Who was that singer??Miller EconotigCutmaster 38Yes ma'am, that IS a screwdriver in my pocket!
Reply:Originally Posted by WelderBoyFrom peening, or what?
Reply:Here we go..I have to stay in "neutral" for awhile...My clutch is getting ready to come apart... ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.Originally Posted by SundownIIIGoose-em,OK  Question.  What happens when the welded assembly is "stress relieved"?Is the weld no longer in tension?
Reply:I experience a bit of tension when a bit of hot slag falls into the open top of my boot that I'm wearing over my bare feet, or when I think of my ex-wife.....
Reply:Originally Posted by denrep"Why are welds held in Tension even when loaded in compression?" I thought this question was a riddle.Sorry, I disagree with the above, especially if we're saying all welds.I agree with those who questioned tension and compression in,  stress relieved, worked, and annealed welds.
Reply:Originally Posted by runchmanI experience a bit of tension when a bit of hot slag falls into the open top of my boot that I'm wearing over my bare feet.
Reply:Originally Posted by Joe HI would guess that a weld is always in tension because of the shrinkage that occurs when cooling.
Reply:Originally Posted by reddoggooseDing, Ding, Ding, WE HAVE A WINNER!!!!!!. Yes the welds are still in tension after stress relief, however the stress levels which can reach as high as the yield point may be slightly lowered but still there. Once the metal has plasitcally deformed there is no coming back. Its all in the AWS Welding handbook Vol. 1 for anyone interested enough to look it up.
Reply:Originally Posted by goose-emAnybody?  Anybody?Birds are singing, crickets are chirping...........Waiting patiently..........
Reply:Here is one case where welding results in compressive residual stress.A weld overlay technique has been used since the early 80's as a long term repair of intergranular stress corrosion cracking (IGSCC) in the stainless steel piping of boiling water reactor systems.  One of the reasons that the weld overlay is effective against IGSCC is that it produces compressive residual stresses in the original weld, through to the inside surface of the pipe.
Reply:I'm in way over my head and will likely drown on this one, BUT....Wouldn't a preheat significantly reduce the internal strain?And everywhere we look there are welds that, as discussed on this thread, have significant internal strain and they are all holding as intended so what's the point?I'm sorry if I over-simplify.P.S. the previous post on the weld overlay technique is most interesting. thanks for that bit of knowlegeDon't talk about it, Just do it!
Reply:Originally Posted by VicoorWouldn't a preheat significantly reduce the internal strain?And everywhere we look there are welds that, as discussed on this thread, have significant internal strain and they are all holding as intended so what's the point?I'm sorry if I over-simplify.
Reply:When Goose first posed this question in a different thread the other day, I had high-hopes he'd answer it since I didn't have a clue. The "expansion-thing" crossed my mind, but I really didn't/don't have the background/experience to come anywhere close to making an educated guess.I also think SundownIII asked a significant question and thus far nobody's bothered to answer him. I'm guessing that Zap answered correctly: SDIII answered his own question; I'm also guessing, and this is just a guess, that 30+ years of engineering--degrees and experience--mean that SDIII already knows the answer and is toying with the rest of us. Guess I'll Wait & See like everyone else....
Reply:Just more food for thought.Physics 101 deals with the concept of equal and opposing forces.As explained by PM to BWS29128(Clint), all material as we know it is under some form of "stress".A sheet of steel, 3'x3'x1" thick, supported on it's four corners, is under both tension and compression.  Just depends on where you want to take your measurements.  Top center is in compression,  bottom center is in tension.Equal and opposing forces keeps things in equilibrium.Just my .02 in layman's terms.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by BWS29128When Goose first posed this question in a different thread the other day, I had high-hopes he'd answer it since I didn't have a clue. The "expansion-thing" crossed my mind, but I really didn't/don't have the background/experience to come anywhere close to making an educated guess.I also think SundownIII asked a significant question and thus far nobody's bothered to answer him. I'm guessing that Zap answered correctly: SDIII answered his own question; I'm also guessing, and this is just a guess, that 30+ years of engineering--degrees and experience--mean that SDIII already knows the answer and is toying with the rest of us. Guess I'll Wait & See like everyone else....