BOUNDARY

Q: How is the nub-valley contact accounted for? I can’t se the contact pressures in XPOST when opening the xx_bflex2010.raf file. Shall it be activated in the VISRES or similar card?

A: You will see the contact pressures directly by looking at the Normal stress (sigma-zz) result type for the boundary group

Q: In BFLEX, which friction coefficient is used for the nub-groove contact in BOUNDARY?

A: The friction coefficient will follow the value provided in the FLEXCROSS input for the corresponding layer.

Q: Nub-Valley friction induced flexlok section transverse stresses (boundary), can they be visualized?

A: Look at Transverse stress (sigma-yy) and Shear stress (sigma-xy) result type for the boundary group

Q: INOD, would there be results differences depending on which INOD is selced?

A: The user can select the position of the boundary model. This is to be able to choose a critical position along for example a bend-stiffener. So yes, changing INOD may mean different curvature histories and hence difference in the boundary and pflex stresses.

Q: The Axial stress results in the -boundary model looks strange?

A: The Axial stress, Normal curvature stress and Transverse curvature stress results are populated by PFLEX, even though the results can be seen in the -boundary model part in Xpost. You should hence perform the PFLEX analysis before the inspecting these results. Note that for the Transverse curvature stress results, the -boundary model results only contain the dynamic, bending induced part of the stresses, excluding the axi-symmetric part.

Q: During tension and pressure loading my boundary model of the zeta profile moves a lot in the transverse direction?

A: Check your transverse curvature parameter trcurp in the *.boi file. If this is zero or very small, an increased value will provide a small transverse stiffness.

Q: I observe a longitudinal stress pattern which are present from the beginning of the analysis, with horizontal stripes of stress variation?

A: For a non-linear material in a pressure spiral, the initial stress-free configuration is straight. (This differs from elastic material, where the initial helical shape is assumed to be stress-free.) Before the analysis load steps are applied, the production-induced stresses are accounted for. Consequently, the pressure spiral is pre-curved to a level that yields a net-zero bending moment for the model’s helix radius. This implies a spring-back from a larger initial curvature, resulting in the stress pattern observed.