reveal zones plastic deformation steel structure

Is "polish and coat with a hard brittle varnish" the answer to this question?
I've made a "square-cornered U" of RHS100x50by8thk (4"x2"by5/16"thk.).
45degree mitres full-pen'd for the two corners. About 150mm (6") between the parallel Rectangular Hollow Sections (RHS) heading towards the open end of the "U". Lying flat, presents the 100mm (4") faces of the RHS (obviously(?!)). It's about 490mm long (about 19") overall.
This was for practicing various skills and getting used to the facilities & equipment - plus the following intention...
I'd like to put a hydraulic cylinder / hydraulic jack toward the open end of the parallel sections forming the "U", and see what happens when it's increasingly loaded.
Precautionary note - one assumes it would be a good idea to lash the hydraulic cylinder with rope to constrain it if it were elastically ejected from its original position...
If things go well and forces pass those necessary to cause yielding - how would one reveal where that plastic yielding is happening? I've heard of polish surfaces smooth and apply a hard brittle lacquer... If so, exactly what type? Economical preferred - this is very rough-and-ready and my own interest. Nail varnish sounds alright - but might not be the cheapest.
I've finite-element'ed the thing and get a prediction of about 8 tonnes force near the outer "open" end to reach general yielding. More accurately - at 250mm from the closed end, the thing should caliper as having grown by 3.9mm across the overall width at the moment at which it starts to yield.
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"Richard Smith" wrote in message
Is "polish and coat with a hard brittle varnish" the answer to this question?
I've made a "square-cornered U" of RHS100x50by8thk (4"x2"by5/16"thk.). 45degree mitres full-pen'd for the two corners. About 150mm (6") between the parallel Rectangular Hollow Sections (RHS) heading towards the open end of the "U". Lying flat, presents the 100mm (4") faces of the RHS (obviously(?!)). It's about 490mm long (about 19") overall.
This was for practicing various skills and getting used to the facilities & equipment - plus the following intention...
I'd like to put a hydraulic cylinder / hydraulic jack toward the open end of the parallel sections forming the "U", and see what happens when it's increasingly loaded.
Precautionary note - one assumes it would be a good idea to lash the hydraulic cylinder with rope to constrain it if it were elastically ejected from its original position...
If things go well and forces pass those necessary to cause yielding - how would one reveal where that plastic yielding is happening? I've heard of polish surfaces smooth and apply a hard brittle lacquer... If so, exactly what type? Economical preferred - this is very rough-and-ready and my own interest. Nail varnish sounds alright - but might not be the cheapest.
I've finite-element'ed the thing and get a prediction of about 8 tonnes force near the outer "open" end to reach general yielding. More accurately - at 250mm from the closed end, the thing should caliper as having grown by 3.9mm across the overall width at the moment at which it starts to yield.
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You would have to test the nail polish to find the elongation that cracks it. In my experience, using it to mark wires, electrical connectors, USB flash drives etc, it's not brittle enough.
Try to buy it from a cute young clerk with a sense of humor. They don't initially know what to make of a dignified and respectable-looking man asking for cheap nail polish in all the rainbow (resistor code) colors.
I'd consider lightly scribing a grid on the metal and measuring it after stretching the frame beyond its elastic limit, where the hydraulic pump handle stops becoming progressively harder to pump. I you have a set of machinists' parallels you could leapfrog them down the frame to keep the line spacing accurate.
I added a tee and pressure gauge to my hydraulic ram kit, and calibrate the rams with a second-hand Tuffaloy spot-welding force gauge. That gauge is presently displaying blade tension on my bandsaw sawmill. I couldn't do much mechanical experimentation without tension and compression gauges that measure up to 1000Kg or more.
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On Sunday, November 15, 2020 at 2:14:47 PM UTC-8, Richard Smith wrote:

...

I'd think, in testing-machine fashion, you'd want to step the pressure (good hydraulic gage required for that) while watching a machinist's dial gage on the deflection. You know what direction it moves... no need for a two-D grid, and buckling would require 3-D before-and-afters. Do multiple pressure trials, relieving pressure and looking for permanent deflection.
I'm not sure I could get full penetration on those internal corners, but maybe cut-a-slot/insert-a-wedge in two or three places could make a U with continuous inner metal, all the welds being under some amount of compression. You'd want to hot-work the bends, of course.
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Thanks for responses. Things moved on a long way quickly.
This is the write up about what I was then in the early stages of... http://www.weldsmith.co.uk/tech/struct/201113_u_rhs/201120_U_RHS_make_analyse_test.html
This one gets testing conditions directed at the test weld http://www.weldsmith.co.uk/tech/struct/201123_wssb_test/201123_weld_RHS_beam_test.html The Lu..ders Bands spall the mill scale - "witnesses" the deformation penetrated around the weld. Found what I wanted... Rich S
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"Richard Smith" wrote in message
This one gets testing conditions directed at the test weld http://www.weldsmith.co.uk/tech/struct/201123_wssb_test/201123_weld_RHS_beam_test.html The Lu..ders Bands spall the mill scale - "witnesses" the deformation penetrated around the weld. Found what I wanted... Rich S
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An Umlaut replaces an "e" after the vowel, as in Lueders. Common usage at least in the US is to ignore foreign accent marks and pronunciations, despite our large immigrant population.
Good job. Too bad the mill scale didn't crack -before- reaching the yield point, that would have been valuable.
Perhaps you've seen a good solution to a similar problem I'm working on. I want to join four 8' C4x5.4 channels into an overhead gantry hoist track 16' long, ie two back-to-back pairs non-permanently joined in the middle. I'm not using a single WF beam because I need each component including the splice to be light enough to carry and lift overhead, as it will be stored disassembled and possibly assembled on a stepladder. http://www.toolsforengineer.com/c4x5-4/
I'd like the central splice to maintain the load capacity of the channels, meaning (I think) no bolt holes that weaken the tension flanges (doublers?). Also the hoist trolley has to roll on the top side of the lower flanges without obstruction. I don't know how to design for full strength with bolts through only the webs and upper compression flanges. The trolley doesn't leave much clearance under the beam for the welded-on leaves of a pinned joint.
The main intended use has it hanging from an overhead beam at the splice, so the minimum design has to support only the load's reaction or the moment of the dead weight during setup.
A full strength splice is really just a design exercise, though it would be useful if I suspend the track from end tripods in the field, or my yard, where I just finished man-handling and sawing 3/4 ton oak logs into beams and have two one-tonners to attack in the Spring.
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You remind me of the common way of substituting for an umlaut
"Boehler" rather that (phonetic representation of the common pronounciation) "bowler".
The "umlaut'ed" vowel sound is unique, isn't it? Not literally represented by removing the umlaut and suffixing with an "e"?
That was alright. Turkish was "the greatest fun". Full respect for the language. I could never do more than catch buses, shop, order meals, etc., extend greetings and simple invitations - but actually rendering those in a conversational way which blended into the flow of everytday events... Lots of sounds in this Middle Eastern language which we don't have. Then their best - they have all these grammatic rules so that say two words convey what we need seven to do - and the vowel sounds harmonise through those words. The mind was on a really thrilling twisting multi-dimensional ride flying all that while you responded to someone who asked if the chair here was free (would they be invited to share this table in a cafe full of people having breakfast on their way to work), etc.
Regards, Rich S
PS - I will try to understand your technical challenge / question. Tired after a working week. Bit later...
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"Richard Smith" wrote in message

You remind me of the common way of substituting for an umlaut
"Boehler" rather that (phonetic representation of the common pronounciation) "bowler".
The "umlaut'ed" vowel sound is unique, isn't it? Not literally represented by removing the umlaut and suffixing with an "e"?
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I was stationed in Heidelberg and points south, where the Schwaebisch dialect is VERY different from standard German, and the neighboring Bavarian isn't much better. https://omniglot.com/language/phrases/bavarian.php
I still can't distinguish between Hochdeutsch and a Swiss or Austrian accent. My German pronunciation is a mix of two years of it in college and a smorgasbord of what I heard.
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"Richard Smith" wrote in message
PS - I will try to understand your technical challenge / question. Tired after a working week. Bit later... -------------------------------------
The 16' gantry hoist track of C4x5.4 channel is for my sawmill. It will hang at its center joint from the front roof beam of a storage shed for 12' long timbers, with 8' of track outdoors over the sawmill to gently load logs onto it, and the other section inside to stack the results. Both ends hang from 10' tripods, probably raised and suspended by cables of boat trailer winches that allow for leveling and readjustment as the tripod legs sink into the dirt. For this use the 8' track sections could simply be pinned or hinged at the center but a stiff connection makes the track easier to install by assembling it on sawhorses and lifting the ends. I avoid muscling heavy steel into place while on a ladder. I usually work alone since the available help isn't up to complex tasks like tying a knot.
The holes drilled in the channels for this supported center splice shouldn't interfere with making the stronger unsupported splice I asked about. I should at least have a good plan for it. Ideally the same splice assembly could serve both uses, however the unsupported splice could arch above the track and the centrally supported one needs to be low to allow more working height for the hoist. Perhaps a bolt-on upper truss allows both?
My question is how to splice the channels without weakening the tension flanges with bolt holes or interfering with the trolley or its wheels. Can it be done with bolts through the web? If a doubler welded to the lower flange is acceptable to maintain cross-sectional area around bolt holes, is there a right/wrong way to weld it without inadvertently adding a stress riser? I need a good overall geometry before calculating the details. There aren't many exposed steel structures around here to examine for clever ideas.
The trolley can be adjusted to clear bolts and nuts joining the webs to a central vertical plate, as on the center splice in the 3" channel. I have about 3' of W6x9 beam that could be reinforced to make the splice. My other scrap structural steel is too heavy to hold in place with one hand while inserting a bolt, and the steel shop where I buy offcuts doesn't have smaller than W8x15.
The shed that stores 12' beams is 19' long by 4' wide, built narrow between two stabilizing end trees to quickly dry freshly cut firewood. The track extends 4' out the back side, over space for a narrow trailer that moves logs and lumber.
I've already borrowed and used the 3" x 16' channel gantry track from a shed that stores 8' lumber but I really need both shed gantry hoists functional at the same time. The C3x4.1 channel has a decent safety margin to lift 8' logs but not 12' ones. I have a 1000 kg crane scale to weigh the loads and stay within my equipment's capacity.
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Great question, but been distracted ("weldsmith" is my site)
New section - "structures" http://www.weldsmith.co.uk/tech/struct/struct.html
Linking from it - Three new projects
http://www.weldsmith.co.uk/tech/struct/201113_u_rhs/201120_U_RHS_make_analyse_test.html
http://www.weldsmith.co.uk/tech/struct/201123_wssb_test/201123_weld_RHS_beam_test.html
http://www.weldsmith.co.uk/tech/struct/201124_fwbeamt/201124_fwbeamt.html "Fillet welds tensile tested in beam test"
Been busy most of the weekend, and working in a steel fab. shop during the week.
Saw that "C3x4.1" is a channel. We have "PFC" - "Parallel Flange Channel". That looks like a tapered-thickness flange specification(?)
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"Richard Smith" wrote in message
Great question, but been distracted ("weldsmith" is my site)
New section - "structures" http://www.weldsmith.co.uk/tech/struct/struct.html
Linking from it - Three new projects
http://www.weldsmith.co.uk/tech/struct/201113_u_rhs/201120_U_RHS_make_analyse_test.html RS --------------------------------------------------- JSW I went through a similar process for the frame of the hydraulic bucket loader I built for my tractor. The square tubing U frame serves as the hydraulic reservoir so all welds had to be oil-tight as well as strong enough to withstand the bucket hitting an immovable rock. It did, and the frame welds held.
To clear the front wheels when turning I had to angle the corners up at 60 degrees from just outside the tractor's frame, then further up, turn another 30 degrees to upright, thus there were four beveled butt joint welds to leak and more chance of distortion. After welding on the cylinder attachments etc the top ends bent inward and I had to jack them back to parallel so the boom pivot pins at the tops of the frame would be in line.
I used a hydraulic pump and cylinder similar to yours, with a hydraulic-rated tee and a pressure gauge inserted between the pump outlet and the hose. Afterwards I removed it because the gauge was too susceptible to damage* if the stiff, springy hose tipped the pump over.
Since the goal was to make both legs parallel I measured the spring-back from beyond the yield point and jacked the legs that far beyond parallel. The gauge wasn't much more useful than the feel of the pump handle to indicate yield.
* These disassemble gauges for repair and recalibration. I made one last week from scrap 3/8" water pipe. (Amazon.com product link shortened) A bag of similar home-made tools got me a job at Segway. JSW --------------------------------------------------- RS Saw that "C3x4.1" is a channel. We have "PFC" - "Parallel Flange Channel". That looks like a tapered-thickness flange specification(?) RS --------------------------------------------------- JSW Yes it is, the channels are former pallet rack horizontals from a recycling company. I assume 36KSI yield for them, unless proof testing shows otherwise. I didn't measure the force to straighten the bent ones because the setup made a formidable crossbow as-is and didn't need a projectile.
My question is if you've seen some clever way to splice beams with bolts (or rivets) without drilling and weakening the tension flange. The pinned fork joints that connect mobile crane sections might do if there could be enough clearance underneath for the trolley.
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"Richard Smith" wrote in message
http://www.weldsmith.co.uk/tech/struct/201124_fwbeamt/201124_fwbeamt.html "Fillet welds tensile tested in beam test"
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That's interesting. The weld test I was expected to pass was a butt joint with 7018 that could survive being folded double on a 50 ton press. The practice steel was 3/16" (5mm) hot rolled CNC plasma cutouts from a reputable metal fab company so I assume it was properly specified, not the random junk I usually use. It did harden at the plasma cut.
Out of curiosity I tried the test on a 1/4" grade 8 bolt. The rolled threads were brittle but the shank bent into a U without cracking.
Cooking steel overnight in the wood stove softens it nicely for machining. Yesterday I hot forged an old lawnmower blade flat and began hacksawing out thin wrench blanks. If the steel doesn't dull a 10-for-$1 hacksaw blade it should be safe to cut with a $25 bandsaw blade.
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