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UNITS:
The Units for Youngs Modulus should be 'Pascals' abbrieviated to 'Pa'
a Pascal is the same as Newtons/Meter^2 (or N/m^2)
You will often find it quoted as MPa (Megapascals) or GPa(Gigapascals)
1 MPa = 1,000,000 Pa
1 GPa = 1,000,000,000 Pa
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TYPICAL VALUES:
On wikipedia typical values for youngs modulus are:
Steel 200 GPa (200 E9 Pa, or 200 X10^9Pa)
Typical Wood 10 GPa (10 E9 Pa, or 10 X10^9Pa)
Glass 72 GPa (72 E9 Pa, or 72 X10^9Pa)
so for Typical Wood that is:
10,000,000,000 Pa as it is in the spreadsheet I believe.
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CONVERSION FROM TABLE ON THIS SITE:
The data in the Kams table is a bit wierd:
The units for youngs modulus should be force / area. The units in the table are in mass / area which is not a valid unit for youngs modulus really. For the conversion I have assumed that 1Kg is equivalent to 10N (this is a commonly used conversion although only valid on earth), so we have:
Table value = 1000Kg/mm^2
=10,000 N/mm^2
=10,000,000,000 N/m^2 (Pa)
This matches the value from Wikipedia so I would assume that you can take the data in the spreadsheet and multiply by 10,000,000 and you have the youngs modulus in Pa which are the units in the spreadsheet.
Like I said the units in the table are a bit wierd because they would imply that the material stiffness would change depending on gravity (which is not true), but this kind of missunderstanding of the difference between mass and force is common so I am 95% sure that the conversion that I have done is correct.
I hope that answers all your questions.
B.
Ski Flex Prediction...
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Has anyone played with this SS much yet? I've been entering Ski dimensions from the gallery here and stuff of my own and anything else I can find. It makes a great comparison tool. Even lets you make a S.W.A.G. at capped skis. Once you enter enough data it gets even better, because you have more to compare. I have found that my current process adds 4-4.5 MM to the thickness of the core. So if I want to copy a skis flex with sandwich construction I just enter the specs for the ski minus the 4-4.5 MM and I have a very close approximation to build the core. Worked great for some salomons we are trying to approximate. We actually came out a bit stiffer as near as I can tell. Most likely due to the ski being wider than the original. You will need to adjust your center to fit some skis, especially twin tipped skis to fit the model better.
Bambi, great tool thanks for putting it out here.
Hafte
Bambi, great tool thanks for putting it out here.
Hafte
One thing to make users aware of... the results are sensitive to the void ratio that you assume (glass fibre to resin ratio). The reason for this is that the stiffness of the ski is very sensitive to thickness (goes up to the power 3). If you use a high pressure in your press then the void ratio will reduce and if you use a lower pressure then it will increase. With this in mind you need to 'calibrate' the spreadsheet to your press, but I found the figures that I have in there to be broadly OK for our press.
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MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
Link to spreadsheet
Here's a link to the file on Rapidshare if any one needs it.
http://rapidshare.com/files/306083069/Skidimmsexe.xls
http://rapidshare.com/files/306083069/Skidimmsexe.xls
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WhiteCloud
- Posts: 4
- Joined: Thu Dec 10, 2009 4:52 pm
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King_of_the_Hill
- Posts: 29
- Joined: Mon Oct 01, 2007 11:48 pm
- Location: Netherlands
- Contact: