even though you can’t see it, a tightened bolt has been stretched a microscopic amount, and this stretch is called Tension.
Just like a stretched spring, which tends to pull back into its original shape, a stretched bolt tries to pull itself back to its normal state. It’s this pulling back force, called the “_______” that actually maintains the tightness of the joint.
Note: But lubrication on the bolt threads—and a whole host of other factors—can cause fluctuation in torque readings. So once you add a lubricant of any kind to the threads, all bets are off as to whether the same torque setting will truly secure the bolt. That’s because nobody really knows how the lubricant affects the torque measurement on a bolt without performing a scientific study using expensive lab instruments.