Al,
A fly in the ointment, or just buzzin. :)
Wishing to further the discussion, let me ask this, when you scribe a line to determine your verification point, your line is based upon the original base metal fusion face (1/2" back). But basing your fillet size verification on the original fusion face is equivelent to basing your verification on the theoretical throat, i.e., the original theoretical unwelded triangle.
Yet engineering calculations are concerned with effective throat. An assumed actual melted metal. The measuring of the fillet leg still assumes a certain depth of fusion. And isn't that the same as I am proposing?
So, wouldn't it be ligit to verify from the top toe of the weld which is more closely related to the effective throat as opposed to the original fusion face.
The problem I see with using the orginal fusion face is that you could have a weld that in actuality is twice what you need (a problem especially on smaller components), given a certain amount of what has been called 'washback' and yet still be verified as too small. The only difference is, your weld deposit is a mix of melted base metal as opposed to just filler metal, which it always is anyway, its just a question of extent, i.e., dilution.
If basing your verification on the top toe of the weld is illigitimate you have to assume that you did not melt the base metal all the way through, sort of a bell shape nugget. In other wods, refusing to assume a certain depth of fusion, which even in your own sketch demonstates you don't make this assumption, and would be consistent with predominant welding results and common fillet symmetry. If you shift your fillet gage to the left until it contacts the toe of the weld you will see that the gage now aligns with the cross sectional visual diagram of the effective throat dimension.
The only other deligitimating argument I can see is that somehow melted base metal is less of a weld, high dilution concerns, etc.
AWS D1.1 Figure 2.1 shows a similar situation. and again, measuring to the top toe is more accurate to the actual dimension of the fillet weld than is measuring from a theoretical throat dimension.
jeff
Jeff,
Thanks for your input as well. I do have a few questions/comments I would for you to expand on if you don't mind.
It was my understanding that engineers calculated there weld size based on the theoretical throat. To my understanding, this is what a fillet gage confirms in the case of a concave weld b/c the depth of penetration can not be determined with out destructively sampling.
In the case of a concave weld I don't know how you can determine acc/rej when you don't know where the original fusion face was.
I can see how the effective throat could be calculated, but it was my understanding that engineers calculate the size of the weld based on theoretical throat b/c it will always be smaller than the effective throat, thus the effective throat is essentially becomes a safety factor.
Additionally, how can you determine the depth of fusion if you don't know where the original weld face was?
Regards, BP
In terms of throat under D1.1 it would be from the root of the joint to the closest distance to the surface as normal. No allowance is given for extra penetration. However I know you can specify a joint with more penetration if you can prove that you can continually achieve that penetration. (as done with SAW.) The first line would represent the effective throat by D1.1, the second would probably be closer to the actual throat. The certification process for that is beyond me though.
*Edit* this might count as a skewed joint with that much washback on the top edge that again is out of my area of expertise.
Forum
