That's what I had stated back at the start of this thread. But that's not correct. As long as the bolt is moving the measurement is dynamic, requiring extra energy. But when the torque spec is met and the fastener stops moving, the measurement becomes static. That would be point A on the hysteresis graph. There is no energy lost within the extension at point A. The loading force (the up arrow line of the hysteresis curve) is equal to the release force (the down arrow line).
The rest of the hysteresis curve is operating under dynamic loading. At a given displacement angle, the loading force is greater than the release force. The difference is the hysteresis force.
Chum lee wrote:
Socket extensions also deform when torque is applied, but, they deform mostly torsionally. It takes energy to do that. As long as the extension is not deformed beyond its elastic limit, it will return to its original condition when the torque is released. Tightening a bolt is a dynamic process, not static.
