How does preloading a screw/bolt create internal forces?

Question

In assembly with a screw/bolt, once there is a preload (applying a force on the screw head to make the two elements stick together), it’s said that a force is created internally. The screw would push the higher element down so that’s a compression, but it’s also said that there is a tensile force implied (as some make the analogy with springs). So in global, how is the preload generating any tensile force?

In: 2

Answer 1

As the screw pushes down on the upper element, the element is pushing back on the underrside of the screw head. Since the threads of the screw are being held by the lower element, the screw is put into tension.

It’s Newton’s 3rd Law:
action = reaction