Investigations of Bolt Loosening Mechanisms : 3rd Report, On the Bolts Tightened over Their Yield Point

Abstract

With regard to the bolts tightened over their yield point and subjected to the tensile load, the relation between the load and the residual bolt clamping force after unloading as theoretically analyzed, and a static bolt loosening test was carried out. It was verified that the theoretical results coincide very well with the results of experiments. And under the same condition a fatigue test was carried out with the measurement of the bolt clamping force, and the following results were obtained : (1) Except the loss in the initial stage, there is no loss of the clamping force. (2) With an increase of the initial clamping force, the residual clamping force and also the bolt fatigue life increase. So, judging from the above results, the tightening of bolts over their yield point has an advantage over the tightening of bolts below their yield point.