Stress determination in fillet weld, of a reinforced and pressurized pipe, employing elastic and elastic-plastic material models, through finite element analysis (original) (raw)

Welding International, 2008

Abstract

The three basic causes for the appearance of stresses in a tube for transporting hydrocarbons are: a) the internal pressure applied to the fluid; b) the residual welding stresses; c) the stresses induced by the resistance characteristics of the earth in which the tubing is laid. The importance of estimating the magnitude of the stresses that act on the tube’s material lies in the advantages of predicting the possibility of failure from the point of view of the material’s resistance or tenacity. In the studies carried out, it has been proved that the potential sites for cracks in a tube that has been reinforced by means of a circumferential steel sleeve, which is the most common method for repairing tubes, are those shown in Figure 1(a). According to the postulations of fracture mechanics, load mode I, in which the principal load is applied normally to the plane of the crack (shown in Figure 1(b)), tending to open the crack, has the greatest practical importance, since the majority of the materials are more susceptible to fracture through normal traction stresses than through tangential stresses. Modes II and III generally do not lead to fracture. The cracks located in the HAZ of the tube (position 2 in Figure 1) suffer load mode I due to the action of the stresses in the direction of thickness. On the other hand, cracks situated in positions 1 and 4 suffer load mode I due to the action of the stresses in the axial direction. According to these specificities, in the present work the stress analysis will be carried out on cracks situated in position 2 and will also take into account the von Mises stress (equivalent tension), the tension in one direction conforms to the zone of the join between the tube and the sleeve, which is the subject of this study (direction of thickness). Stress determination in fillet weld, of a reinforced and pressurized pipe, employing elastic and elastic-plastic material models, through finite element analysis

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