ABSTRACT
Consider a flange connection, a system comprising two flanges with a gasket between them, held together by bolts (see Figure 11.1). The loading history is shown in Figure 11.2 in schematic form. The loading begins with the assembly, when the bolts and nuts are closed manually. This is followed by the application of torque to tighten bolts, thus introducing an initial strain in bolts and flanges. Final, the flange connection is subjected to an internal pressure load. As the system is pressurized, the parts become deformed, and the contact between the flanges and the gasket recedes. At a critical pressure, the flanges separate, and leakage takes place. The system’s behavior poses two interesting engineering problems, which are given a special attention below. One problem concerns flanges’ disengagement under pressure, while the other relates to the expansion of flanges at a rate different from that
of the gasket, which causes sliding with friction. The solution to both problems: the diminishing contact and the friction require a nonlinear analysis and complex numerical computations. The two objectives to be achieved include defining the bolt forces caused by loading and predicting the critical pressure that is present as the flange connection starts to leak.
