ANALYSIS OF PRELOADED BOLTED JOINTS UNDER EXPONENTIALLY DECAYING PRESSURE

Dynamic properties of joints must be considered when designing complex structures. A good deal of investigation has been carried out for a b etter understanding of the dynamic behavior of mechanical joints. It i s suitable initially to identify the parameters of a mechanical joint by using either experimental modal analysis or accurate finite element model, and then predicating the behavior of closure bolting system by means of spring-mass-damper model. The effect of bolt prestress on th e maximum bolt displacement and stress has been treated. The loading i s assumed to be initially peaked, exponentially decaying internal pres sure pulse acting on the closure. The dependence of peak bolt stresses and deflections on the bolt prestress level and system damping is inv estigated. It has been shown that the derived formulas, if damping is neglected, reduce to those reported in the literature. Furthermore, th e damping effect is shown to be most important, especially for large n atural frequencies, longer loading duration and lower levels of prestr ess. Existence of damping, which results in the reduction of maximum b olt displacement and stress, was shown to be beneficial, especially fo r longer loading duration. The importance of bolt displacement reducti on from the viewpoint of fatigue life, vibration loosening, and sealin g, especially for lower values of prestress, has been fully emphasized .