Weld between pipe and plate (AWS D1.1)

By Michael.sim Date 05-02-2016 09:44

Hello everybody !

I need your help :)

I need to design a circular weld between two parts, as shown by the picture.

The weld will work under fatigue condition, in torsion. I can't find any recommendation on that kind of weld in the aws D1.1 2008.
I assume it is a tubular connection, and when i try to find the maximum allowable stress for cyclic solicitation, i thought it was maybe the C2 category of table 2.7, and then a maximum stress of 50MPa according to figure 2.13 (meaning that the maximum stress variation is 50MPa ??)

Anyone can confirm that statement, or help me to find information ? My main problem is that i can't find chapters on weld of "pipe on plate"

Thank you very much

By 803056

Date 05-02-2016 23:48

It is not a tubular connection, i.e., there is no pipe or tubing involve. Essentially, you have to plates that are circular that are welded together.

I do not have D1.1 handy since I'm on the road in North Carolina this week. However, you have a situation where you have a thick plate transitioning to a thin plate. The change in geometry, i.e., thickness, acts as a stress riser. The severity of the change could be reduced by tapering the transition from thick to thin. That would improve the fatigue life of the weldment.

The analysis could be handled with FEA by analyzing a thin slice through the joint. The magnitude of the change in load must exceed a threshold value and the number of cycles must exceed 10,000 cycles before fatigue is an issue. Another factor is, the magnitude of the change in load is just that, the difference in the high and low unit stress. In short, there is no need for there to be a complete reversal of load to lead to fatigue, just a change in the magnitude. The magnitude of the load must be within the elastic range or the S-N curves published in AWS D1.1 do not apply.

Best regards - Al