The Irwin--Corten model (18) predicts RCP critical pressure by applying linear elastic fracture mechanics (LEFM) analysis to a pipe geometry.
Davis (24) proposed, "the critical pressure must therefore counteract this closing moment before providing a sufficiently high crack driving force for propagation.
The crack front will be dragged back on the bore surface increasing the fracture resistance and thus increasing the critical pressure.
Also, as temperature increases, plane stress fracture resistance increases and more work is required to separate the ligament at the bore surface, which increases the critical pressure further.
When the "negative flaring" due to residual stresses is low, the crack surfaces are twisted outward and the crack front dragged back on the bore surface, increasing the fracture resistance and the critical pressure.
It was shown in this work that both the FS and S4 Pc results for pipe of equal diameter and different wall thickness can exhibit lower critical pressures with decreasing pipe wall thickness.
As such, S4 critical pressure (Pc) results must be converted into equivalent FS Pc prior for design and specification purposes.
S4 critical pressure tests at 0[degrees]C were performed by Chevron Phillips Chemical Company LP at their Research Center in Bartlesville, OK, in accordance with the ISO 13477 standard (2).
Relative to the S4 test, the FS tests yields higher values of critical pressure for pipes tested at the same temperatures.
Using the formulas discussed in that section, we could calculate the total critical pressure drop from the observed apparent critical shear rate.
The combination of this result with the slight decrease in the capillary pressure drop, leads to a decrease in the total critical pressure drop (or possibly a minimum at [Alpha] [approximately equal to] 30 [degrees]), as seen in Fig.