TPT May 2010

A rticle

Figure 8 : Circumferential strain-pressure curve of specimen A0

Figure 10 : Radial deformation-pressure curve of specimen A0

Figure 9 : Comparison of circumferential strain-pressure curves of specimens A4, A7 and A13

Figure 11 : Comparison of radial displacement-pressure curves of specimens A4, A7 and A13

Figures 8 and 9 show circumferential strain-pressure curves of specimen A0 and comparing between specimens A4, A7 and A13, respectively. Nonlinear elastic behaviour before occurrence of initial buckling is visible in curves, clearly. In Figures 10 and 11 the radial deformation of specimen A4 and comparing between three other specimens in experimental study are plotted in some selected nodes of pipe wall. FEM buckling and post buckling modes Figures 12 and 13 show radial deformation of models in FEM analysis study. Figure 12 shows radial deformation-pressure curve of model A0 with 7.1 Kpa and 18% difference with experimental result. Figure 13 shows this character for models A4, A7 and A13 with 18.1 Kpa, 32.4 Kpa and 49.8 Kpa which have 6%, 16.5% and 24% differences with experimental results (table 2). When comparing experimental and FEM curves, some differences are shown, such as value of initial buckling pressure or post- buckling part of curves which occurred with pressure decreasing in the experimental study and with the constant load carrying capacity in the FEM study. This is because of some problems such as unabling in modelling residual stress. As mentioned above, additionally, two models were analysed in terms of investigating the effect of rings thickness on the behaviour of pipeline. These models are compared with model A4. Models A4 t20 and A4 t0.25 had four rings with 20mm and 0.25mm thickness respectively while the basic model (A4) had 2mm thickness. Model A4 t20 was 26.05Kpa and model A4 t0.25 with 18.8 Kpa initial

Figure 12 : Radial deformation-pressure curve of model A0

Figure 13 : Comparison of radial displacement-pressure curves of models A4, A7 and A13

108

M ay 2010

www.read-tpt.com

›