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Long-term hydrostatic (LTH) capacity test up to 10,000 h of polyethylene pipe (PE pipe) was successfully conducted according to Arrhenius theory. It was revealed that in some cases the pipe damage points initiate within the marker line on pipe body, indicating that the addictive of marker line could somehow weaken the mechanical property of pipe base materials. Test pressure test time data was fitted using dual-parameter model under the guidance of ISO9080: 2012, and its serving life was calculated as 28.9 years, ductile-brittle transition point was found at 8456 h. Conclusions drawn from this paper could contribute to understanding the long-term mechanical behaviour of PE pipe. [ABSTRACT FROM AUTHOR]

The mechanical behaviors of steel strip–reinforced flexible pipe (steel strip PSP) under combined axial extension → internal pressure (T → P) load path were investigated. Typical failure characteristics of pipe samples under pure internal pressure and T → P load path were identified in the full-scale experiments. A theoretical model for pipe under tension load was proposed to capture the relationship between axial extension of the pipe body and stress state of the steel strip. Numerical study based on finite element (FE) method was conducted to simulate the experiment process, and good agreement between FE data and experiment results were observed. Sensitivity study was conducted to study the effect of some key parameters on the pipe antiburst capacities in T→P load path; the effect of preloaded internal pressure on the pipe tensile capacity in P→T load path was also studied. Useful conclusions were drawn for the design and application of the steel strip PSP. [ABSTRACT FROM AUTHOR]

This paper discussed the aging behaviour of Kevlar fibre reinforced flexible pipe subjected to long-term monotonic internal pressure. Multi-group of pipe internal pressure tests that last for 10,000 h were conducted. The pressure-time curves of each test samples were collected. Two typical failure modes of the samples were specified. Linear regression analysis of the original pressure-time data was conducted and expression between characteristic pressurePand service timeT, which is capable to provide fast evaluation of pipe qualification, was presented. Based on suitable selection of safety factor, the design pressures under different service time were calibrated. Analysis shows that the LTHS50/LTHS10 ratio meets the requirements claimed by ASTM D2992, thus these calibrated design pressures can be used for engineering practice. [ABSTRACT FROM AUTHOR]

Based on the three-dimensional (3D) elasticity theory, this paper presents the mechanical properties of steel strip reinforced thermoplastic, cross-section view of such pipe plastic-steel-plastic (PSP) under internal pressure. The steel strip reinforced PSP pipe consists of four layers. Mises yield criterion is introduced to predict the damage of the pipe on layer 2. Further a 3D finite element model is established in ABAQUS to compare with the theoretical model and the result shows good agreement with each other in terms of hoop stress and axial stress, which means the proposed elastic model is feasible and can be applied and updated to study the elasto-plastic properties of steel strip reinforced PSP pipe in future research, and serve as a guide to the forthcoming experiments. [ABSTRACT FROM AUTHOR]

Plastic pipe reinforced by helically cross-winding steel wire (namely PSP) is a novel kind of composite pipe which consists of an inner high-density polyethylene layer, steel wire layers and an outer polyethylene coating. PSP has the potential application as subsea pipeline. Based on numerical 2D ring model, proposed by Yong Bai, the wall thickness change, transverse shear deformation and pre-buckling deformation have been considered in the collapse investigation of PSP under external hydrostatic pressure. Based on finite element method, reinforced layers were taken as transverse isotropic material, and equivalent elastic modulus was obtained based on Halpin–Tsai model. It is shown that steel wires layer has little effect (just 0.2% difference) on the behavior of PSP under external pressure. The external pressure–ellipticity and external pressure–hoop strain curves derived from the theoretical method and finite element method are compared and show a good agreement (deviation of buckling pressure is 1.4%). Finally, maximum experimental external pressure values of two pipe specimens were obtained by increasing hydrostatic pressure in a closed cylinder. The results of theoretical analysis and finite element method are in great agreement with the experimental values. [ABSTRACT FROM AUTHOR]