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sm�ller-21-Visitor
1-Visitor
February 6, 2019
Solved

Autofrettagediameter

  • February 6, 2019
  • 2 replies
  • 7114 views

Hallo,

 

i have a Formula to calculate the elastic plastic transition diameter for autofrettage:

 

Dp is the elastic plastic diameter. The problem is i need to plement the calculation for DP into microsoft excel.

I need a formula to directly calculate DP. Now im using the solve function in excel but the solver is not trustable and does not give always a result where a result is calculateable.

 

Is there a way to transform the equation so that DP=..... for microsoft excel?

 

Transforming gives this block in Mathcad

 

where RE Yield Stress @20°C

Di inside diameter

Re Outside diameter

 

lg

Stefan

Best answer by Werner_E

Maybe you don't have to dig into the subject that deep.

What about this thread

http://www.office-loesung.de/ftopic524762_0_0_asc.php

and the link in the first  post.

Or maybe this ready made plug-in can be useful: https://github.com/mdscheuerell/Lambert-W-in-Excel

2 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
February 6, 2019

The function you found using mathcad uses the LambertW() function. Please find out first if Excel knows/supports that function.

The conversion to string should not be difficult. If you save your files as Mathcad 11, I can (try to) convert it to string just like:

LM_20190206_Convert2string.png

But... As said: Your Excel needs to support the LambertW function, and I have my doubts about that...

 

Success!
Luc

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Werner_E25-Diamond I
25-Diamond I
February 6, 2019

Excel seems not to include a ready made Lambert-W function but if you search the net you'll find a lot of links showing how to implement that function (e.g.: http://bfy.tw/MA2i)

The rest seems to be just a lot of tedious and failure prone typing work but, alas, we know that Excel sure is not the right tool for math and engineering work.

 

You may also want to simplify the formula first. E.g. Re cancels and does not have any influence. You also can cancel De^2, etc. This sure would make it a bit easier to convert the formula.

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LucMeekes23-Emerald IV
23-Emerald IV
February 6, 2019

I don't see Re cancel, You can divide it on P, to make life simpler. But you can do the same with 2/sqrt(3)...

Anyway, I put the equation in Mathcad 11, solved it and converted it to string:

LM_20190206_Convert2string.png

And to save the tedious retyping here is the string:

1/(-Di^2/De^2/LambertW(-Di^2/De^2*exp(-(RE-P*3^(1/2))/RE)))^(1/2)*Di

 

Success!
Luc

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    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    February 6, 2019
    @LucMeekes wrote:

    I don't see Re cancel, You can divide it on P, to make life simpler. But you can do the same with 2/sqrt(3)...

    Re is yield stress, P is pressure.  The units are the same (force/area), so they can be (as you have) divided to cancel out.

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