THERMAL DILATION FORMULA?

[cranekiran]

Dear all,

I want to know a good formula for calculating thermal dilation or expansion of a steel shaft w.r.t temparature.
For eg:- If I have a shaft of dia. 12.7mm at room temp. then at what temp. will the shaft contract to dia. 12.5mm?
Thanks in advance.

 

[TerryB]

Calculating expansion due to temperature is as follows :-

Lc = Lo x a x t

Where :-
Lc = Change in length or diameter
Lo = Original length or diameter
a = Coefficient of linear expansion
t = Temperature change

For steel a = 0.000012/deg.C

You need to find t so rearrange formula

t = Lc / (a x Lo)

For your problem temperature change needed to produce required contraction is -1312 deg.C

Not sure how to achieve this.

Hope this helps
Terry

 

[anandvidhate1]

impossible to attain this temperature.

 

[radomir]

Unfortunately absolute zero (no atom movement, not even oscilation) is at -273.14 deg.C. Theefore you can not shrink your 1/2" dia shaft for a little bit less than 0.010" by cooling it down. You have to skim it.

 

[radomir]

Sir Crane-kiran this is a P.S. to my previous message. It suddenly crossed my mind that you may want to put something on that shaft with an interference fitt (overlaping). The possible way is to cool that shaft in liquid Nitrogen (N) and warm the other part in an owen. But frankly speaking 0.2 mm interference fitt seems a little bit too much. For example bearings are usually installed on shafts with 0.01-0.03 mm interference fit.