`Guthrie weld toe fatigue research`

Guthrie's career at the British Welding Institute developing TIG dressing, full-penetration welds, and machined toe profiles to recover the strength-fatigue benefit lost in as-welded fillet joints.

The reason for that is that weld toe profile is never perfect. If you could make a perfect weld — that's what Guthrie back in the 60s kind of made part of his career at the British Welding Institute. He was showing that you could get the fatigue strength with higher-strength steels up if you did several things. One, you can machine it. That's a little expensive to go along a fillet weld. If you have a fillet weld between two plates and you just put a weld in like this, you'll get a stress concentration at that toe. You may have an undercut anywhere along the length of that, going back in three dimensions. So anywhere along the length is going to be where the fatigue crack starts. There's a very high probability you're going to have a higher stress concentration than at one cross-section. The worst cross-section along that length is where the fatigue crack is going to start.