The principle of prestressing is mainly embodied in the working way of the saw. The tightened-rope on the saw exerted a pretension on the saw blade to withstand the repeated stress of pulling and compressing, thus avoiding the failure of the saw blade with low bending resistance.
When the saw blade moves to cut wood, one part of the saw blade is pulled and the other part is pressed. The thin, narrow blade does not have any compressive capacity of its own, but is subjected to pretension stress due to pretightening of the rope, which occurs when the pretension stress exceeds that of the saw. The saw blade will always be in the pull state, so as not to bend instability damage. This is a typical example of the use of pretensile stress to resist the pressure stress that occurs during use.