Numerical and experimental investigation of liner wrinkling and strain localisation in mechanically lined pipes under bending

Corrosion-resistant alloy (CRA) liner wrinkling and strain localisation at the triple point present significant challenges to the structural integrity of mechanically lined pipes (MLPs), particularly in girth-welded and weld overlay configurations subjected to bending. This study combines numerical and experimental approaches to evaluate the onset of liner wrinkling and strain localisation at critical weld interfaces. A finite element model (FEM) was developed in ABAQUS and validated against full-scale bending test (FSBT) results. The FEM accurately predicted the mechanical response of MLPs, including wrinkling initiation, deformation patterns, and local axial strains in the triple point region. Strong agreement was achieved between numerical predictions and experimental data, with wrinkling initiation occurring at global tensile strains above the acceptance criteria defined by the Det Norske Veritas (DNV) Joint Industry Project (JIP) guidelines. A parametric study further explored the influence of weld overlay length and internal pressure on wrinkle formation and strain localisation. The results show that while weld overlay length has little effect on wrinkling onset, its local stiffening reduces strain localisation near the triple point. In contrast, internal pressure has a pronounced stabilising effect, substantially delaying liner wrinkling and allowing the pipe to withstand higher bending strains before instability occurs.