minimum fillet weld size vs design

[alimse]

Hello every one. I have a question and I wish u all can solve my problem. can an engineer use the minimum fillet weld size data in AWS D1.1 without designing the size of fillet? I mean can the numbers recommended in Aws use instead of design or these are just recommendation? please answer my question according to aws d1.1 and adress your words.

Thanks
mseali

 

[alimse]

I mean that if I use these data according to aws d1.1 and the structure fails, can any body tells me its your fault? what aws tell about these data...

 

[metengr]

Code requirements are minimum requiremen's for safety. With that said you should verify adequacy of design. What does that mean? Verify by calculation.

 

[Tmoose]

How are you selecting the thickness etc of the members being welded?

 

[alimse]

all of the plate thicknesses in this project is over 20mm.

 

[Tmoose]

hi alimse,

" all of the plate thicknesses in this project is over 20mm."

That is the answer to "how thick are the plates,"

But it is NOT the answer to my question "How are you selecting the thickness etc of the members being welded?"
I'm wondering what method or analysis was used to select the thickness (and other dimensions) of the welded components and the final assembly.

 

[gtaw]

The minimum fillet and groove weld sizes listed by D1.1 are not based on strength, but on metallurgical considerations. The minimum size groove and fillet welds are to ensure sufficient heat input to assure slow cooling (assuming the appropriate preheat is used) to prevent a hard, brittle microstructure in the HAZ.

The footnotes for each of the two tables (minimum groove weld or minimum fillet weld size) involved require single pass welds if the SMAW electrode or welding process are not recognized as low hydrogen. If the welding process or the SMAW electrode used meets low hydrogen requirements, single pass welds are not a requirement.

One must use the larger weld size, either the minimum weld size based on base metal thickness and heat input or the weld size determined to transfer the applied load from one member to the next.

You may have noticed AWS D1.1 does not address seal welds. Seal welds are used to seal a connection to prevent moisture entering between the members of the connection and corroding. It is assumed the seal weld is not subjected to stress. Instead, the minimum weld size is required even if it is assumed the weld transfer no loads. The justification is that there is no such thing as a weld that transfers no load. At the very least, all welds are subject to the residual stresses as a result of the thermal history.

Best regards - Al

 

[alimse]

thanks gtaw for your answear. I got it.

 

[WKTaylor]

alimse

Most welding specs only set-up the procedure/materials and project expected outcomes with expert welding methods techniques and quality materials in controlled circumstances.

HOWEVER, In almost all of the weld specs I'm aware of [aerospace and related support equipment, etc] there is an UPFRONT acknowledgement that tests which coincide with the 'real-world' are the only genuine way to verify the strength and character[ization] of critical welds. A minor flaw/processing variation, poor material selection, variable welders skills and quality, non-ideal welding circumstances, etc... including the introduction of unforeseeable factors... can radically alter the outcome of a welded joint, both good and bad. I have personally confirmed the validity of this approach... and over years of experience have developed my own rules of thumb for how to proceed in my element: welding for structural repair of aircraft parts that have seen a LOT of service [when-to, when-not-to]. 'Sacrifices' sometimes have to be made for the greater good of reliability!

Regards, Wil Taylor

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