Concavity @ Fillet welds 1

[gokhanusn]

Eventhough we sometimes reccomend to have a convexity at fillet welds to eleminate the high strain which may lead to long'l cracks that might occur during cooling down, it has a certain limit in ISO 5817 but there is no defined limit or any other info at the same source for the concavity.

Would anyone know a standard that describes the concavity limits?

Thanks!
Gokhan

 

[hogan666]

I have not worked to the referenced ISO, but I believe that this would fall under the throat limitations.

 

[DVWE]

I agree. Take a look at AWS 3.0 standard welding terms and definitions. Figure 25 depicts it very well.

 

[valkyrie77]

Please see attached file

 

[valkyrie77]

sorry about that,here's the file

 

[strider6]

are u sure that is better to have a convex vs a concave fillet weld?
"The convex fillet is generally undesirable for two main reasons. a)The junction of the weld metal with the parent metal at the weld toe can form a significant stress raiser and will adversely affect both fatigue life and brittle fracture resistance; b) the excess weld metal in the cap costs both time and money to deposit without contributing to joint strength. The concave fillet weld can be beneficial with respect to fatigue strength and, if required, the minimum throat thickness MUST be specified."

http://www.twi.co.uk/content/jk90.html

S



Corrosion Prevention & Corrosion Control

 

[valkyrie77]

my apologizes, i made a mistake. please take a look at the attached files. from the attached files you can see that the fillet weld with convex weld profile is with concentrated stress points(stress risers). the weld with concave weld profile, however, has a smoother stress transition. it is better for the weld profile to have a concave profile. i agree with hogan666.

 

[valkyrie77]

here's another file

 

[Mr168]

The excess weld metal argument is somewhat moot in comparing convex vs concave fillets, as the legs must be extended on a concave fillet to achieve the same throat dimensions.

In theory, the profile and smooth transitions of a concave fillet are desirable. However, its really more of a practical applications approach as to why the convex or flat fillets prevail, and that is crack prevention.

When a convex weld shrinks during cooling, the surface is placed in compression. With a concave weld, the surface area is placed in tension upon cooling, and is far more susceptible to cracking. This tends to be of far more concern (and a more commonly seen issue) than the stress transitions, and many of the notch effect issues don't come into play until you have excessive surface convexity outside of most code limitations.

 

[gokhanusn]

Just a quick note; I agree with Mr168.

strider6; Tech. details can be found in the following link (see pg. 42, right column) to back it up.

Thank you all!
Gokhan