I've seen this acronym a lot on this forum, and I think I have it figured out to be Finitite Element Analysis... What software do you people use to figure out the load a press can take? Is there a software that is easier to use than others?
Esscher
what is FEA?
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To be honest FEA/FEM won't really get you anywhere (in useful time), but it can be fun just playing around with, make little animations etc.
Just use common sence, depending on your construction the bolts and nuts are probably going to break first. You have to make the press strong and stiff, (thick beams) and if it's about to break you will probably get some mechanical warning (things bending, loud cracking noises etc.) Then you run.
I used Catia as a student, worked great for showoffs and fancy presentations, but it hasn't really taught me anything.
Just use common sence, depending on your construction the bolts and nuts are probably going to break first. You have to make the press strong and stiff, (thick beams) and if it's about to break you will probably get some mechanical warning (things bending, loud cracking noises etc.) Then you run.
I used Catia as a student, worked great for showoffs and fancy presentations, but it hasn't really taught me anything.
Actually yes,
My friend and I were thinking of a way to easily establish core dimensions using FEA. I think that's where it would be really helpful. You don't really need FEA for press frame. I posted the way I used to calculate press structure in an other part of the forum.
http://www.skibuilders.com/phpBB2/viewtopic.php?t=1309
French E
My friend and I were thinking of a way to easily establish core dimensions using FEA. I think that's where it would be really helpful. You don't really need FEA for press frame. I posted the way I used to calculate press structure in an other part of the forum.
http://www.skibuilders.com/phpBB2/viewtopic.php?t=1309
French E
I would be tempted to not try and separate the epoxy from the glass layers, it would be better to use the combined strength of the laminateFrench-E wrote:The only problem I see with FEA (I am studying in mecanical engineering) is that I didn't find a way to simulate epoxy.
French E
since they are working together and those figures are reasonably easy to approximate or get from manufacturers.
Tony
haha there is def more value to FEA then just cool simulations. We used cosmos, the FEA add on to solidworks to design our frame. IF your not making center supports you can generate some serious stress in a press, and its better to overdesign then to fling a bolt across the room or have it snap when your leaning on it.
That being said you'll never get an accurate simulation unless you really take the time to accurately model all the bolts/welds and constraints, but it will direct you to the points of highest stress, which may not be where you'd thought theyd be and atleast tell you you've got some factor of safety. Also, if you plan on doing some level of production you need to over design to account for cycling up and down which could enduce wear.
oooor just over build the crap out of it and move on.
the skibuilders guys broke their press, so its certainly possible.
That being said you'll never get an accurate simulation unless you really take the time to accurately model all the bolts/welds and constraints, but it will direct you to the points of highest stress, which may not be where you'd thought theyd be and atleast tell you you've got some factor of safety. Also, if you plan on doing some level of production you need to over design to account for cycling up and down which could enduce wear.
oooor just over build the crap out of it and move on.
the skibuilders guys broke their press, so its certainly possible.
I also use solidworks and cosmos professional on my work.
Today I prepared the model of a ski and started to work on the fea.
in the 1st step I've decided to constrain "fixed" the 2 fixing areas of the bindings and apply a force equally distribuited on the edge or on the base.
In your opinion, this is the right solution to simulate? do you tryed other simulation solution?
I will also try to impose the ski deformation during a 30° turn and display the reaction forces.
Today I prepared the model of a ski and started to work on the fea.
in the 1st step I've decided to constrain "fixed" the 2 fixing areas of the bindings and apply a force equally distribuited on the edge or on the base.
In your opinion, this is the right solution to simulate? do you tryed other simulation solution?
I will also try to impose the ski deformation during a 30° turn and display the reaction forces.
beansnow wrote:haha there is def more value to FEA then just cool simulations. We used cosmos, the FEA add on to solidworks to design our frame. IF your not making center supports you can generate some serious stress in a press, and its better to overdesign then to fling a bolt across the room or have it snap when your leaning on it.
.........................
oooor just over build the crap out of it and move on.
the skibuilders guys broke their press, so its certainly possible.
I used a program called ANSYS for all of my Finite Element Analysis. My main reasons: I wanted to design a frame with a safety factor >1 (for obvious reasons), but I also wanted to know what and where the maximum deflection would be in the press.
Also, since I have approximately 26 different pieces (not including fasteners) doing a hand calculation would have been almost impossible.
However, one important thing to take note. If you don't have access try to get one of the guys on this forum to do a simulation for you. Most of these programs cost upwards of $10,000 US. You can buy a lot of extra steel with that.
Also, since I have approximately 26 different pieces (not including fasteners) doing a hand calculation would have been almost impossible.
However, one important thing to take note. If you don't have access try to get one of the guys on this forum to do a simulation for you. Most of these programs cost upwards of $10,000 US. You can buy a lot of extra steel with that.
How do you propose doing this? The deformation and reaction speeds in the real world will vary with snow hardness, speed, slope of hill and a multitude of other factors.Zigor wrote:
I will also try to impose the ski deformation during a 30° turn and display the reaction forces.
Not trying to pick apart your ideas here - I'm genuinely interested. I'll be doing FEA models of boards later this year (through either CATIA or ANSYS) to compare with lab testing, but it will be restricted to verifying the torsional modes and frequencies.
If I could figure out how to model a snowboard in a dynamic sense and get usable data I would but for the life of me I can't figure out how, too many variables.
I'm new on this forum and I iust started to think about ski building, so I'm not and expert and, if something i wrote is wong or already treated in other posts please advert me.
If I want to build ski I can:
1-copy a commercial model
2-use a custom project available on the web
3-project a new one (naturally taking information from commercial, custom, forums)
To project a new one I will:
a-select lenght, radius, width from other skis that i like
b-project right thickness, rigidity, vibration response,..
At that point I need to decide how to simulate ski behaviour.
What type of behaviour I must search? I need a constant pressure of the edge on the snow or I need to find the perfect carving?
So my question is: what is the better simulation for a pair of skis and what is the force value that I must impose?
-to verify security I can “fix the binding” and impose a force on the tip and/or tail to simulate a terrain gibbosity or a wrong landing
-verify pure longitudinal flex I think is not very interesting by itself ( but really important during a turn)
-to verify the behaviour during a turn I can “fix the binding” and impose a constant (is true?) force on the internal edge. I will obtain the core stresses (security) and deformation profile. But the deformation profile is not a perfect carving and is really strange profile that I think is not the real situation during a ski turn
-to verify the core behaviour during a turn I can impose the perfect carving (the ski flex itself in order to reproduce the right radius in function of ski inclination) and evaluate the core stresses in order to harmonize them. Simulate this will be quite difficult, because is necessary impose a deformation to curve (released edge) to curve (carving line)
If I want to build ski I can:
1-copy a commercial model
2-use a custom project available on the web
3-project a new one (naturally taking information from commercial, custom, forums)
To project a new one I will:
a-select lenght, radius, width from other skis that i like
b-project right thickness, rigidity, vibration response,..
At that point I need to decide how to simulate ski behaviour.
What type of behaviour I must search? I need a constant pressure of the edge on the snow or I need to find the perfect carving?
So my question is: what is the better simulation for a pair of skis and what is the force value that I must impose?
-to verify security I can “fix the binding” and impose a force on the tip and/or tail to simulate a terrain gibbosity or a wrong landing
-verify pure longitudinal flex I think is not very interesting by itself ( but really important during a turn)
-to verify the behaviour during a turn I can “fix the binding” and impose a constant (is true?) force on the internal edge. I will obtain the core stresses (security) and deformation profile. But the deformation profile is not a perfect carving and is really strange profile that I think is not the real situation during a ski turn
-to verify the core behaviour during a turn I can impose the perfect carving (the ski flex itself in order to reproduce the right radius in function of ski inclination) and evaluate the core stresses in order to harmonize them. Simulate this will be quite difficult, because is necessary impose a deformation to curve (released edge) to curve (carving line)
Alex13 wrote:How do you propose doing this? The deformation and reaction speeds in the real world will vary with snow hardness, speed, slope of hill and a multitude of other factors.Zigor wrote:
I will also try to impose the ski deformation during a 30° turn and display the reaction forces.
Not trying to pick apart your ideas here - I'm genuinely interested. I'll be doing FEA models of boards later this year (through either CATIA or ANSYS) to compare with lab testing, but it will be restricted to verifying the torsional modes and frequencies.
If I could figure out how to model a snowboard in a dynamic sense and get usable data I would but for the life of me I can't figure out how, too many variables.
Last edited by Zigor on Thu Apr 15, 2010 6:35 am, edited 1 time in total.
It's an interesting process for design. All of the people I'm aware of design by trial and error with regards to core thickness and sidecut radius.
Please keep us updated, I for one am very interested in your work and the results you come up with, especially the on-snow performance when you finally get there.
We have a group of Mechatronics PhD students at my uni on exchange from France who are doing their combined doctorate on building a robot that simulates on-snow performance of a snowboard. I haven't been in contact with them yet, but I plan on having a chat soon.
Please keep us updated, I for one am very interested in your work and the results you come up with, especially the on-snow performance when you finally get there.
We have a group of Mechatronics PhD students at my uni on exchange from France who are doing their combined doctorate on building a robot that simulates on-snow performance of a snowboard. I haven't been in contact with them yet, but I plan on having a chat soon.
Unfortunately I need informations about forces to apply to the ski.
how many kg I have to simulate? I never read documentation with "real" number.
I've found some interesting graph about deformation vs a fixed force( http://www.skibuilders.com/phpBB2/viewt ... on&start=0) but notting about real forces. Somebody can provide me these informations?
how many kg I have to simulate? I never read documentation with "real" number.
I've found some interesting graph about deformation vs a fixed force( http://www.skibuilders.com/phpBB2/viewt ... on&start=0) but notting about real forces. Somebody can provide me these informations?
I'd start with Newton's third law; for every action, there is an equal and opposite reaction. Thus, the forces of the snow pushing against the ski will be approximately equal to the force the skier is putting down ie: the skier's weight. Obviously it will get more complex with combined loading due to friction, acceleration, etc.