In great majority of situations, bolted flanges are designed to work well within elastic limits. The main design considerations concern preload which should be high enough to limit fatigue loading of the bolt and also prevent flange opening in the operating range. Elastic design of bolted joints as well their finite element simulation have been well understood.

The present paper deals with post elastic behavior of bolted joints. Equipment and structures are often exposed to loads much higher than the normal operating loads. Civil engineering structures experiencing earthquakes is one such example. Military ships and submarines are subject to torpedo loads and other types of blast loads. Aircraft engines are subject to ultimate load conditions such as fan blade-off (FBO) and foreign object damage (FOD) like bird-hit. To meet such eventualities it is uneconomical to attempt elastic designs. The approach is to go for plastic designs. The criterion is that the structure or equipment can yield and distort but should not rupture. The philosophy is that the distorted parts are replaced once the event is over. Bolted joints are invariably present in these categories of equipment.

The present paper deals with simulation and structural behavior of components fastened together by way of threaded fasteners. Sector of bolted flange is considered for study and elastic-plastic analyses are carried out. This is an extension of the work carried out earlier by the authors for simple axisymmetric joints. The earlier study was for conceptual understanding. In the present study focus will be on design aspects. Three different simulation models are compared. In addition, parametric studies are conducted to get deeper insight into structural behavior.

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