Linear metal expansion - For an Old timer

[DHA]

Hi all

I am a newbie here, so please go gentle

It is along time since I have had to use Thermal Co-efficients of expansion for various metals.

However, I am trying to tie in some figures I have been given to what I know to be reality.
i am sure that I am doing something basically wrong, or the whole theory of such science will hve to be re-written

Now I know that aluminium expands at a rate of 1 or 2 mm per metre ( depending on colour ) I am involved here with the flashings on buildings , so thicknesses from 0.9mm to 3mm thick )

Given that knowledge ( unless the building industry is wrong ) I have been given a co-eff of 22.2 x (10 power -6) m/m K (Not sure how to get -6 as supertext )

How do I relate that back to a dimension of 2mm or so that I am familiar with ( I am sure I can not count the right number of zeros ) but hey it's well over 40 years since I did this and a good 50 since I did it at school

Much appreciated

A confused Old Timer

DHA
PS Perhaps I should add ~ I am moving decimal point 6 places to left, then 3 to right (to bring to mm ) obviously wrong as it is no where near ??

 

[nasu]

When you say 1-2mm expansion for 1 m bar, what is the temperature change producing this expansion?

 

[NascentOxygen]

given a co-eff of 22.2 x (10 power -6) m/m K

Hi DHA! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

That means for every degree Celcius it is heated, each metre of length (and thickness) expands by 0.0000222 metres (i.e., by 0.0222 mm).

So a 100°C rise would see each metre of it stretch by 2.22mm.

 

[DHA]

OK Forgot about temp difference, How thick am I ?

Thanks

 

[pmacias]

Hello Old Timer,

It sounds like you are trying to understand how to apply thermal coefficients of expansion to the flashings on buildings. Let me help clarify some things for you.

Firstly, the thermal coefficient of expansion is a measure of how much a material expands or contracts when its temperature changes. It is usually represented by the symbol alpha (α) and is expressed in units of length per unit of temperature (such as mm/m/K). So, for example, if a material has a thermal coefficient of 1 mm/m/K, it means that for every degree increase in temperature, the material will expand by 1 millimeter for every meter of length.

Now, in your case, you mentioned that you have been given a thermal coefficient of 22.2 x (10^-6) m/m/K. This means that for every degree increase in temperature, the material will expand by 22.2 millionths of its original length for every meter of length. To relate this to a dimension of 2mm, you can simply multiply 22.2 x (10^-6) by 2. This gives you a result of 0.0000444 mm, which is a very small amount of expansion.

In terms of your confusion with moving the decimal point, it is important to remember that the thermal coefficient of expansion is a very small number and it is common to use scientific notation to represent it. The negative exponent indicates that the number is very small and to move the decimal point to the left. So, in your case, you would move the decimal point 6 places to the left to get 22.2 x 10^-6.

I hope this helps clarify things for you. If you have any further questions, please don't hesitate to ask. Keep up the good work in the building industry!