landroversforever Posted August 19, 2015 Share Posted August 19, 2015 Are there any strength/rigidity differences in the final panel between the dimple dies with and without a 'return' on the edge of the dimple? These type just have the chamfer in the corner: http://www.satchellengineering.co.uk/tool.html These ones have the extra flat bit on the die so it makes another edge on the swage: http://www.ebay.co.uk/itm/5-8-Hole-Swage-Dimple-Die-Swager-Autograss-Seven-Locost-Flaring-Tool-Sheet-/291453595690?hash=item43dbfcf02a Would either one produce a stronger profile on the dimple? Calling SimonR and Bishbosh Quote Link to comment Share on other sites More sharing options...
simonr Posted August 19, 2015 Share Posted August 19, 2015 I think the difference is largely aesthetic. My gut feeling (without analysing it properly) is that just a 45 deg chamfer will give the highest rigidity. Si P.S. If I get bored later, I'll run FEA on it just out of curiosity! Quote Link to comment Share on other sites More sharing options...
simonr Posted August 19, 2015 Share Posted August 19, 2015 Well, I was curious! My gut feeling was wrong! Without a dimple. The results on the left are for a simple dimple and on the right with an additional flat bit. The dimple with the extra bit gives 30% less deflection for the same load case. 47% less than a flat sheet. Si 1 Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 That's brilliant . Thank you very much Si..... dimple set with the return it is then Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 Do you do the FEA within solidworks or use an external program such as ANSYS? Quote Link to comment Share on other sites More sharing options...
simonr Posted August 19, 2015 Share Posted August 19, 2015 Just the Simulation Express in Solidworks. It's fine for the vast majority of situations IMHO. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 Very useful. I've not looked to see if my copy of catia can do FEA. So looking at your analysis.... is it stiffer with the dimples of either type over the flat sheet? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted August 19, 2015 Share Posted August 19, 2015 Found this interesting, just cos I am a nerd: http://mint-design.ca/design/dimple-die-rules-of-thumb-testing/ Clearly they're not giving everything away, as it is their business. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 That is interesting, I seem to remember that being posted before so thanks for bringing it to my attention again! Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted August 19, 2015 Share Posted August 19, 2015 That really suprised me, love reading this forum Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 That really suprised me, love reading this forum Echo that! I'd assumed the non flat type would have been stronger! Quote Link to comment Share on other sites More sharing options...
simonr Posted August 19, 2015 Share Posted August 19, 2015 Very useful. I've not looked to see if my copy of catia can do FEA. So looking at your analysis.... is it stiffer with the dimples of either type over the flat sheet? Most copies of CATIA don't have the analysis built in (at least in my experience). They assume that if you can afford £20k for the software, you'll think nothing of spending another £50k on one of the analysis tools. In most companies using CATIA you end up having a specific dept which deals with the analysis. I hate CATIA! Any kind of dimple will be stiffer than none. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 19, 2015 Author Share Posted August 19, 2015 Just having a play and it would appear that it does have it .... However I've only ever used ANSYS for FEA and that was a few years ago now. I know what I want to do, but not sure how . I've got it meshed roughly for now, just trying to work out how to put on the constraints and loads. Quote Link to comment Share on other sites More sharing options...
De Ranged Posted August 20, 2015 Share Posted August 20, 2015 I'm surprised by this result...... enough I might machine up some more die's I was under the impression (from comments on OFN) that the commercially available ones that have the lip edge somewhere around 1/4 the drilled hole's size, effectively replaced the strength lost from the hole so the only gain was weight, its why with mine I made the lip size half the hole dia to try and make a gain Did you dimension the holes the same (dia at base of dimple and hole dia) so the lip on the second is just formed from some of the dimple wall ? By the way thanks for running this.... I've always been keen to play with FEA but its beyound my budget lol Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 20, 2015 Share Posted August 20, 2015 Ooooh science! Very interesting stuff too. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted August 20, 2015 Author Share Posted August 20, 2015 Let the dimpleing commence Quote Link to comment Share on other sites More sharing options...
simonr Posted August 20, 2015 Share Posted August 20, 2015 Did you dimension the holes the same (dia at base of dimple and hole dia) so the lip on the second is just formed from some of the dimple wall ? I made a guess at the relative sizes of the 45 deg bit and lip. Both dimples have the same OD and start with the same size hole - so the amount of metal involved in the dimple is the same in both cases though the ID will be different once pressed. Si Quote Link to comment Share on other sites More sharing options...
simonr Posted August 20, 2015 Share Posted August 20, 2015 I'm surprised by this result...... enough I might machine up some more die's I was under the impression (from comments on OFN) that the commercially available ones that have the lip edge somewhere around 1/4 the drilled hole's size, effectively replaced the strength lost from the hole so the only gain was weight, its why with mine I made the lip size half the hole dia to try and make a gain The dimple doesn't increase the strength of it - just the stiffness. If you want strength, don't drill any holes as they lead to stress concentrations. If you want something to be stiff - a panel you don't want to vibrate for example - then a dimple will help. In the above example, I am twisting the sheet (well within it's elastic limit) and applying the same torque in each case - looking at how much it deflects. That's not to say you can't drill holes to lighten a component without impacting it's strength - but you have to know about how it's going to be loaded. If you don't know - don't drill the holes. Si Quote Link to comment Share on other sites More sharing options...
De Ranged Posted August 20, 2015 Share Posted August 20, 2015 Lol and right there is an example of the difference between some one with a formal background and me..... by strength I ment stiffness Thanks for the dimension stuff, think it might be time for me to scrape together some offcuts and try a few profiles, I bend 3mm in mine and forming a second lip in my press (60 ton) is going to depend on the depth of the second lip, so a bit of trial and error to see how much on the die results in a flat plane and not just a radius..... hmmm I wonder if I play with reliefs, play with the shape of the die.... machine out the female side of the bends and extend the male edges.... this would make the dies more "tuned" to a certain thickness tho.... this sucks working away from my workshop lol I'll have to wait till I'm home to play 1 Quote Link to comment Share on other sites More sharing options...
discomikey Posted August 22, 2015 Share Posted August 22, 2015 Well, I was curious! My gut feeling was wrong! No Dimple.jpg Without a dimple. SimpleDimple.jpgDouble Dimple.jpg The results on the left are for a simple dimple and on the right with an additional flat bit. The dimple with the extra bit gives 30% less deflection for the same load case. 47% less than a flat sheet. Si Nice to see an actual measured result (albeit theoretical), what is the Von Mises and FOS like for all 3 cases, does a lower deflection come at the cost of a higher stress (and therefore lower fatigue life), or does it actually reduce stress? Either answer i wouldn't be surprised as a correctly placed hole in a highly stressed plate can actually reduce the stress by spreading it more evenly through the plate. (although it tends to increase deformation) needless to say a badly positioned and dimensioned hole and/or sharp corners dramatically increase stress levels. Very useful. I've not looked to see if my copy of catia can do FEA. So looking at your analysis.... is it stiffer with the dimples of either type over the flat sheet? there is less deformation with either type over plain sheet, although the one with the secondary return is less again. this suggests a higher stiffness. Quote Link to comment Share on other sites More sharing options...
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