This is an excellent rationale for using a calculation tool like Mathcad or SMath Studio. I can imagine the millions of hours lost every year tracking down a unit error in some calculation.

BTW, isn't "ton" an English unit; should that be a "tonne"?

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1 tonne = 1000 kg, and not 1e6kg as stated in your conversions

For stress analysis, IPS (inches, pounds-force, seconds) is popular in the US (probably the most popular). Also, stress analysts typically work with base units of length-force-time (not length-mass-time). You can use either, but the "base" should not consist of multiple units.

Brian
www.espcomposites.com

Sorry, as said by corus, the worksheet attached to my first post has a mistake: 1 tonne = 1.0e+3 kg, not 1.0e+6 kg.
I've attached a corrected version of the worksheet (link below)

As for the other comments:

- it's true that the table is biased towards the metric system. It is because I don't have much contact with the Imperial system, so any one who think it's appropriate, feel free to enrich the table;

- it was good to mention that, for stress analysis, it is often more convenient to define a set of units based on length-force-time (in a static loading case, for example). I totally agree with that, and that is why the set mm-N-s is in the top of the list. But "base quantities" is a standand "notation" in physics. For dimensional analysis, it was conventioned that those seven quantities are the base quantities - they are independent from each other, and all units can be described as a relation of base units.

Anyway, even if you need a set based on units for length-force-time, it is still easy to find the right line in the table, and them find the correspondent units for time, stress, velocity, etc

• http://files.engineering.com/getfile.aspx?folder=1ca12ff4-1186-44ed-a546-6e

Can you add the FFF system?

The length unit is the furlong, the mass unit is the mass of a firkin of water, and the time unit is the fortnight.
http://en.wikipedia.org/wiki/FFF_system

Alternatively, there's the “Furlong / Fortnight / Farad / Faraday” system, whose consistent unit of mass is the faraday² fortnight²/(farad·furlong²)
http://dausha.net/furlong-firkin-fortnight-system#...

http://julianh72.blogspot.com

am pretty sure 1000 kg is 1 tonne, not 1 ton.....

The Wikipedia ton page covers the various meanings of "ton" and "tonne" pretty well:

http://en.wikipedia.org/wiki/Ton

except that it calls it a unit of weight, whereas the tonne (in engineering usage)is a unit of mass.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/