How to calculated a fiber elongation for pipe Cold Bending

[2468jjcr]

Hi

Any one can help me find out how to calculated fiber elongation after bending as per ASME B31.4 para 332.4.2 (a)

Please help.

Thanks

C.P.

 

[israelkk]

The radius outside of the bend is larger than the mid radius. Therefore the outer fiber is longer. Calculate the outside perimeter of the tube and deduct the mid perimeter.

 

[metengr]

I have a copy of ASME B31.4 and B31.3, there is no 332.4.2 in B31.4, there is in B31.3.

So, the fiber elongation limitation can be calculated as follows;

measure a pre-determined distance on the extrados of the bend (before actual bending). After the bending operation, measure this distance and subtract the two and divide by 100 = % fiber elongation. You use the OD surface of the extrados because this is where the maximum fiber elongation will ocurr.

You had better re-read 332.4.2 in ASME B31.3 because for certain materials, the fiber elongation is limited to 50% of the minimum reported elognation for the material. This means that if the material has a 25% tensile elongation on the material test report, you will be limited to 50% of this value (12.5%) for cold working, otherwise you will need to heat treat the material to remove the effects of deformation from cold bending.

 

[2468jjcr]

Million thanks sir.