Yes I have been playing with the FEM work bench in freecad. There is also a full blown FEA program from the french power company EDF it is open source and used to build all the french nuclear reactors and hydro electric projects so it is very robust and well audited. It is written in fortran and coments and a lot of the documentation is in french but interesting non the less.
My back ground is helicopters and I have spent a lot of time dealing with vibration balancing and trying to figer out what is causing things to crack and sake apart. As an as side with the introduction of the new digital balance gear and the possibility that brought we had lots of odd things come up as it was now possible to balance things to well and unmask vibrations that were hidden in the back ground noise before. Vibration analysis can tell you a lot it is more a trend monitoring thing rather than the actual values good base line data is always good as you can see something is not the same as yesterday and I better figer out what is changing and how quickly as most vibration related issues progress exponentially. On 15-11-09 02:03 PM, Gregg Eshelman wrote: > On 11/8/2015 4:13 AM, linden wrote: >> yes this is a big issue rigidity and vibration damning have >> traditionally been done by increasing the mass and by using cast iron >> that has a natural tendency to absorb and dissipate vibration. >> >> You can build very rigid light wait structures but most of these have >> harmonics like a tuning fork. These vibrations would not be good for >> your surface finish and on the other hand if you built every thing out >> of cast iron with a mass of several thousand kg your speed and >> acceleration are limited. >> >> The trick is to build a rigid machine with light moving parts that >> absorbs vibration. Every thing is a compromise trying to find a >> compromise that will accomplish what you need is where the fun is. > When the vibration properties of a material in various sizes and shapes > are measured, it's possible to closely calculate the vibration of the > material in an arbitrary shape. > > Finite Element Analysis (FEA) has been used for quite a while for things > like engines and transmissions but doesn't seem to have made much, if > any, inroads into machine tool design. > > For vehicle parts, FEA is used to reduce weight while improving strength > and reducing vibration or adjusting vibration frequency to values that > are non-harmful to the part and not annoying to occupants. > > But with cast iron machine tools the majority of them still seem to be > designed using the rule that more mass is always best. > > In some severe duty cases it has been found that much less mass than > seems logical is what's required. One case was in a new model of Benelli > semi-automatic shotgun. Benelli wanted to design the absolute shortest > stroke action possible to work with the length of shells the gun was to > use. The prototypes kept breaking a part of the extractor. > Paradoxically, the thicker and stiffer they made the part, the fewer > cycles it took to break it. In a flash of insight, one of their > engineers tried making the part thinner than the first one which broke. > The thinnest version wouldn't break. Further analysis showed that no > matter how thick and stiff the part was made, it would still flex. That > would fatigue it until it would snap. The thinner version could flex > without fatigue. > > For something like a knee mill column, there's likely plenty of areas > where thick sections of cast iron are doing little except make the thing > weigh more. A single wall isogrid design might be plenty strong enough, > possibly every bit as good, maybe better, at vibration damping and it > would weigh a lot less and cost less by using less metal. > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > > ------------------------------------------------------------------------------ > Presto, an open source distributed SQL query engine for big data, initially > developed by Facebook, enables you to easily query your data on Hadoop in a > more interactive manner. Teradata is also now providing full enterprise > support for Presto. Download a free open source copy now. > http://pubads.g.doubleclick.net/gampad/clk?id=250295911&iu=/4140 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Presto, an open source distributed SQL query engine for big data, initially developed by Facebook, enables you to easily query your data on Hadoop in a more interactive manner. Teradata is also now providing full enterprise support for Presto. Download a free open source copy now. http://pubads.g.doubleclick.net/gampad/clk?id=250295911&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
