Welding technology

Die Kerbe looks as if it ought to be the kerb at the edge of a British pavement, and it is nothing of the kind. It is a notch: a small V cut or worn into an edge, the mark a knife leaves in a stick. The kerb in German is der Bordstein. In a welding shop the difference matters, because the notch is where a joint gives way. Die Einbrandkerbe is the groove the arc melts out along the edge of a weld and never fills again, and die Kerbwirkung, the notch effect, is the reason anybody worries about it: stress crowds into the bottom of any notch, so a crack can start there under a load the rest of the joint would carry without complaint. Read Kerb- at the front of a German compound as notch every time, and a good part of the answer to why a weld tears is already in the word.