Why is Convex bad?

[Lucky Bob]

Any idea why that wouldn't apply to outside corners?

I'm not sure about percussive impact, as that's a whole different kettle of fish, but as far as sustained loads are concerned, it's pretty simple. If you have a sharp inside corner, that means the (imaginary) lines of force have to make a really sharp turn around that, and that means they bunch up and cause a higher effective load. On the opposite side, on an outside corner, they have plenty of space and can "apex" the corner without being forced too much together. Basically, if you're limiting the room for these imaginary lines of force, you're going to cause issue, but if you have extra room, that's not a problem.

 

[hickman1]

I'm not sure about percussive impact, as that's a whole different kettle of fish, but as far as sustained loads are concerned, it's pretty simple. If you have a sharp inside corner, that means the (imaginary) lines of force have to make a really sharp turn around that, and that means they bunch up and cause a higher effective load. On the opposite side, on an outside corner, they have plenty of space and can "apex" the corner without being forced too much together. Basically, if you're limiting the room for these imaginary lines of force, you're going to cause issue, but if you have extra room, that's not a problem.

IE. you have a stress riser that concentrates force in a localized area versus allowing it to spread out over a larger area