## Table of Consistent Units - stress analysis

## Table of Consistent Units - stress analysis

(OP)

I am posting this motivated by another thread (thread727-136030: Consistent Units for Thermo-Mech Analysis: Consistent Units for Thermo-Mech Analysis), that made clear how many mistakes people make when using units.

As discussed there, we can choose any set of units for the base physical quantities, and then the values for all physical quantities must be consistently defined based on the basic units chosen. The base quantities are:

- length

- mass

- time

- temperature

- electric current

- amount of substance (mol)

- luminous intensity

For stress analysis, usually only the first three are used. The table below offers some useful set of units for stress analyses:

I sent the same table in an Excel sheet, that can be print and keep at the desk.

As discussed there, we can choose any set of units for the base physical quantities, and then the values for all physical quantities must be consistently defined based on the basic units chosen. The base quantities are:

- length

- mass

- time

- temperature

- electric current

- amount of substance (mol)

- luminous intensity

For stress analysis, usually only the first three are used. The table below offers some useful set of units for stress analyses:

I sent the same table in an Excel sheet, that can be print and keep at the desk.

## RE: Table of Consistent Units - stress analysis

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

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## RE: Table of Consistent Units - stress analysis

## RE: Table of Consistent Units - stress analysis

Brian

www.espcomposites.com

## RE: Table of Consistent Units - stress analysis

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

## RE: Table of Consistent Units - stress analysis

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 faraday

^{2}fortnight^{2}/(farad·furlong^{2})http://dausha.net/furlong-firkin-fortnight-system#...

http://julianh72.blogspot.com

## RE: Table of Consistent Units - stress analysis

## RE: Table of Consistent Units - stress analysis

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/