Tjin: “Fatigue” is certainly the correct English term for how metal parts gain small stress fractures over time and lose strength as a consequence.

I’m no metallurgist but I believe you’re correct that aluminum suffers from fatigue at almost any loading (albeit small amounts).

While not practical for mountaineering situations, my favorite rappel device is the rappel rack;

https://www.rocknrescue.com/product/smc-nfpa-long-6-bar-rappel-rack/

Developed in 1967 and enhanced/improved since then, it is safe and relatively foolproof.

Most of my rappels lately have been down sea cliffs abd canyon walls to retrieve fossils, which I suppose is a relatively specialized use - also used by window washers, etc...

Here is one of the first dog leg carabiners. They were a marvel on quick draws when they first came out. Notice how a gate pin at the notch just fell out. I got rid of the batch after that happened.

[img:left]https://blog.owareusa.com/#jp-carousel-1627[/img]

Can't seem to get the image to show. Anyone have suggestions?