3-D Finite Element Simulation Of Bolted Flange Joint Considering Gasket Nonlinearity

In this thesis, a three-dimensional parameterization finite element model of a standard bolted necked flange joint is built. With the joint taken as a whole to considering the effect of interaction between all parts of the joint and the connected parts such as elliptical head and cylindrical shell. The gasket nonlinearity is also considered in the model. With this model, the deformation and stress distributions of the flange joint are calculated, and the influences of different parameters such as geometrical parameters, bolt pre-tightening load and pressurizing load, on integrity and tightness of the joint are systematically studied. The findings of the study could give us some information for better understanding and rational design of bolted flange joint.Some important conclusions can be drawn from this analysis are as follows. After bolt pre-tightening, the compression of gasket is not uniform, the outer part being more compressed than the inside part. Pressuring will cause a separate trend further reducing the gasket compression and further increasing its non-uniformity. The highest stresses are located at the conjunction of head and flange and at the conical neck due to the discontinuity. The bolt is not only subjected toaxial tension force, but also bending moment. During pressurizing, when the residual compressive stress on some points of the gasket is reduced to mp, it means that the pressurized medium has already reached these points, leaving the outer annular part of the gasket being tight to seal the medium. With the increasing of internal pressure, the width of the sealing annular part is continuously decreased, and finally, if the medium reaches the outer edge, the sealing annular part on the gasket is lost, and leakage takes place.