Originally Posted by
Kontact
Elastic deformation is when you flex something, and it springs back. You can do this with spoke elbows - flex them via tension until they contact the flange. This puts the bend under tension, like a preloaded spring, and that sprung elbow is going to react to tension variations from rolling by subtly changing shape. Essentially, it will try to curve away from the flange when the spoke nipple is pointing to the pavement, and flex back as the tension goes back. These cycles work harden the point on the elbow that changes shape the most. And you can observe this in used wheels as the spoke elbows backing away from the flange as tension goes toward zero.
How is the elastic deformation of the elbow different from the elastic deformation of the spoke? We want the spoke to elastically stretch. It's one reason why butted spokes are better since they stretch more than straight spokes at the same tension.
The answer: it's not different.
Elastic deformation does not work harden. Plastic deformation work hardens.
Plastic deformation is when you flex something far enough that it no longer springs back. Anyone who has cold set a steel frame from 126 to 130 dropout spacing knows that to get to 130 you have to flex the frame well past that point until you actually deform the metal. Once deformed, the new shape of the frame is a 130 with no tension or force holding it there. That is what elbow setting is - deforming the spoke permanently to a new elbow bend that matches the flange contour. Once that happens, the spoke elbow does not change bend shape as tension is applied or removed, there is no spring effect at the elbow and it does not work harden from the cycles of road contact.
But again, since elastic deformation does not work harden the spoke, why does the spring of the elbow matter? Especially if the elbow is held in position by tension?