PSI - Issue 60

Dhanesh N. et al. / Procedia Structural Integrity 60 (2024) 456–470 Dhanesh et al. / StructuralIntegrity Procedia 00 (2019) 000 – 000

467

12

To create the numerical model of dented pipeline and assessment for protection against potential failure modes, finite element analysis is performed using general-purpose finite element software ABAQUS/CAE 2019. 5.1. Protection against plastic collapse In order to assess the resistance to plastic collapse, an elastic-plastic finite element analysis is performed on the model of dented pipeline segment with residual stresses and strains to determine whether the pipeline response to the progressively applied loads would remain stable at the maximum applied load, i.e., to determine whether the numerical solution would converge at that load point. This assessment is performed in accordance with ASME B&PV Code, Section VIII, Division 2 (2021), Part 5. As per Table 2D.4 of API 579-1/ASME FFS-1 (2021), here all the loads are increased by a factor of 1.944. The analysis is performed for the critical load case (Design Internal Pressure + Gravity + Vehicular Loads) causing plastic collapse mode. The variation of peak equivalent plastic strain (PEEQ) at the dented location with the load factor is plotted in Fig.13. Since the convergence is attained for the entire range of analysis, the pipeline segment with dent passes elastic-plastic analysis for collapse.

Fig.13. Load factor Vs peak equivalent plastic strain (PEEQ) at the dented location

5.2. Protection against local failure An elastic-plastic analysis is performed on the dented model with residual stresses and strains using the loads stipulated for local strain criteria. This assessment is performed following Clause 5.3 of ASME B&PV Code, Section VIII, Division 2 (2021), Part 5. The following load combination is considered for the plastic collapse check: 1.53 x (Design Internal Pressure + Gravity + Vehicular Loads) The local strain check can be performed following the procedure given in Clause 5.3.3.1 or 5.3.3.2 of ASME B&PV Code, Section VIII, Division 2, Part 5. The strain limit damage calculation procedure in Clause 5.3.3.2 is adopted here. From the elastic-plastic analysis, the accumulated strain limit damage (DUCTCRT) excluding the strain limit damage from forming is obtained from ABAQUS. Fig. 14 shows the contour plot of DUCTCRT in the dented region of the pipeline at the end of all analysis steps. The maximum DUCTCRT in the dented pipeline is 0.64. The maximum accumulated strain limit damage in the dented pipeline including the forming strain is D ɛ = 0.745 < 1, hence acceptable.