Linear metal expansion - For an Old timer

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Discussion Overview

The discussion revolves around the thermal expansion of metals, specifically aluminum, and the application of thermal coefficients of expansion in practical scenarios such as building construction. Participants explore how to relate theoretical coefficients to real-world measurements and clarify the implications of temperature changes on material dimensions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant expresses confusion about the thermal expansion of aluminum, noting a discrepancy between their understanding and the coefficients provided, specifically questioning the coefficient of 22.2 x (10 power -6) m/m K.
  • Another participant asks for clarification on the temperature change associated with the stated expansion of 1-2 mm for a 1 m bar of aluminum.
  • A participant explains that the coefficient indicates that for every degree Celsius increase, each meter of aluminum expands by 0.0000222 meters (0.0222 mm), leading to a total expansion of 2.22 mm for a 100°C rise.
  • The original poster acknowledges the need to consider temperature differences and reflects on their own understanding of the calculations involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial confusion regarding the thermal expansion figures, and the discussion remains unresolved regarding the correct interpretation and application of the coefficients in practical scenarios.

Contextual Notes

The discussion highlights potential limitations in understanding the relationship between temperature changes and physical expansion, as well as the need for clarity in converting units and interpreting coefficients.

Who May Find This Useful

Individuals interested in material science, engineering applications, or those working in construction and needing to understand thermal expansion in practical contexts may find this discussion relevant.

DHA
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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 ??
 
Last edited:
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When you say 1-2mm expansion for 1 m bar, what is the temperature change producing this expansion?
 
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 celsius 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.
 
Last edited by a moderator:
OK Forgot about temp difference, How thick am I ?

Thanks
 

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