Change of internal radius design on rectangular tube.
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: Change of internal radius design on rectangular tube.
: Change of internal radius design on rectangular tube. -- triumphguy62	Post Reply	Top of thread	Engineering Forum

Posted by: jboggs ® 01/27/2011, 15:58:09 Author Profile eMail author Edit

First - Those are some pretty detailed questions. Just to make sure they are properly interpreted I would suggest posting a diagram showing visually what you are proposing. Second - Assuming the properties of steel might not be wise since you already know that the initial failure mode (cracking at the radius root) is not like steel at all. Third - You said you want to make the internal walls "longer". Do you mean "thicker"? Fourth - This seems like an ideal question for the manufacturer, especially since they are the ones that will have to make the section for you. They already know all the answers to these questions. And lastly - you are increasing the stress concentration factor by decreasing the radius. Maybe the thicker wall compensates for that. Maybe not.

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: : Change of internal radius design on rectangular tube.
: : Change of internal radius design on rectangular tube. -- jboggs	Post Reply	Top of thread	Engineering Forum

Posted by: triumphguy62 ® 01/27/2011, 16:15:51 Author Profile eMail author Edit

Here is a diagram of what I want to do. The current design is on the left side, my theoretical proposal is on the right. The manufacturer does not know the answer, I asked. I'm thinking that since the stress concentration is focused on the root of the radius, increasing the length of the vertical walls will help increase the deflection rate before it is transfered to the root of the radius. If I'm correct, I'm trying to figure by how much, either way.

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: : : Change of internal radius design on rectangular tube.
: : : Change of internal radius design on rectangular tube. -- triumphguy62	Post Reply	Top of thread	Engineering Forum

Posted by: Pinkerton ® 01/27/2011, 16:42:19 Author Profile eMail author Edit

Not meaning to hijack your approach, but wouldn't this be more a function of the way the fiberglass strands are laid up? The weakness is likely to be more in the resin than the fiberglass. My gut feel for this and having worked in fiberglass many years back, is that the fillet section is actually more rigid than the walls and therefore cracking would begin at the weakest point of the transition to radius. Decreasing radius and increasing the wall length would just move the fracture point without any appreciable efficacy. My feeling here is you are attacking the effect and not the cause. Can you first helical-wrap the tube form with stranded tape then shoot the chopped strand over that? Dave

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