Issue 50

M. Belhamiani et alii, Frattura ed Integrità Strutturale, 50 (2019) 623-637; DOI: 10.3221/IGF-ESIS.50.53 630 parameters Value C 1 -106,8316 C 2 -110,8433 C 3 -1,3366 C 4 0,0011 C 5 864,0942 C 6 9.1156E-3 C 7 3.7582E-4 Table 2 : Model’s parameters. Figure 7 : Comparison of the FE results with the predicted model. The obtained model provides a coefficient of determination R²= 0,979 with eight degree of freedom and the root of the average squared errors (or residuals) of the model (RMCE) is 0,174 for a convergence criterion about 1E-5. Second criterion The aim of pressure vessel design is to avoid structural failure of the vessel during its specified design life.The expression excessive plastic deformation can be used to describe two forms of failure: structural or global failure due to formation of a global plastic collapse mechanism and local failure due to material instability. In this study, the procedures for limit and elastic-plastic design are considered. Limit analysis assumes an elastic-perfectly plastic material model and small deformation theory. At limit state, any increase of load leads to failure through violation of equilibrium. In design based on limit analysis, the limit load is defined as the load causing gross plastic deformation in the vessel. To gain confidence in the present FE limit analysis, the plastic limit pressure solutions for uncracked pipes from the present FE analysis are compared with the published solution of Hill [27] and to validate the efficiency of the application of the repaired bonded composite system, by this second criterion we start the validation of our numerical models.