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Calculating required bend strength


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#1 Supe

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Posted 19 March 2009 - 07:26 PM

Been a couple years since I've taken any statics courses, and I haven't used any of it since, so hopefully you guys can help me out. A friend is trying to determine the necessary strength needed to bend a test strap around a die (I'm assuming he wants to use a hydraulic jack setup, but I don't have all the details). Test straps are typically A36, though A514 and a lot of our high chrome pipe straps are also tested which exceed 100 ksi. Any thoughts as to how to approach it?




#2 MA_PE

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Posted 19 March 2009 - 08:52 PM

QUOTE (Supe @ Mar 19 2009, 03:26 PM) <{POST_SNAPBACK}>
Been a couple years since I've taken any statics courses, and I haven't used any of it since, so hopefully you guys can help me out. A friend is trying to determine the necessary strength needed to bend a test strap around a die (I'm assuming he wants to use a hydraulic jack setup, but I don't have all the details). Test straps are typically A36, though A514 and a lot of our high chrome pipe straps are also tested which exceed 100 ksi. Any thoughts as to how to approach it?


you're showing 7/16 clear on the inside pf your form. Is that the thickness of the strap?

I don't have a reference in front of me but you should look for tables of plate thickness versus minimum bend radius. You're really after the outside fiber strain (which is related to stress by E) to make sure you don't crack the outside radius surface.

Hope this helps some.

#3 Supe

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Posted 19 March 2009 - 09:09 PM

That would be the strap thickness, or slightly less in this situation.

This jig is what they use to typically perform root, side, and face bends for a destructive weld test. They cut a section transverse to the weld joint approximately an inch wide. They'll bend a given number of them in these fixtures after etching, and any tears in the weld metal or heat affected zone are then assessed for accept/reject criteria. That jig is based on ASTM standards. Why he needs to actually determine the bending force required is a little beyond me, as it's typically a "medium sized bottle jack" kind of engineering when we're in the field...

#4 MA_PE

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Posted 19 March 2009 - 09:21 PM

most direct way is to get an existing test fixture and put a load cell inline with the jack and measure the force.

#5 Supe

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Posted 20 March 2009 - 12:40 PM

QUOTE (MA_PE @ Mar 19 2009, 04:21 PM) <{POST_SNAPBACK}>
most direct way is to get an existing test fixture and put a load cell inline with the jack and measure the force.


Pretty much my take on it. No point in him trying to reinvent the wheel.




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