How to calculate the minimum required elongation?

Elongation in % = (½ tube / radius) * 100
Tubedimension (mm)    Radius             Elongation in %
                             
 
What is a 2D curve?

The next rule can be applied. Change the tube dimension from a metric dimension to a (*nominal tube diameter) inch dimension. 

Radius = inch * number D * 25.4
Example 2D: tube dimension Ø 60.3 
Ø 60.3 = 2” (nominal tube dimension)  
Radius = 2 * 2 * 25.4 = 101.6 mm 
* Pipeschedules 

Calculations restistances moment 

Tubedimensions (mm)   Wall (mm)                   I/v cm³