Decompression Point

The point at which there is zero pressure at the joint interface as a result of forces applied to the joint.  If the applied force is increased beyond the decompression point, a gap will form at the interface.  Analytically, a criteria of joint failure is often taken as when the applied force on the joint reaches the decompression point.  This is because forces acting on the bolt(s) can dramatically increase at this point.  Loading beyond this point can also result in fretting at the interface that will lead to bolt tension loss that will subsequently lower the decompression point.  This process can continue until bolt failure does occur.  The failure can be by fatigue or other mechanism but the underlying cause was loading of the joint beyond the decompression point.  It is for this reason that it is frequently taken as a failure criteria in analysis work.