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3.5 The influence of pressure on the FEA pipe model
The aim of this section is to study the influence of the internal pressure on the
model shown in Figure 3.2. This study assumes the pipe is perfectly straight and there is
no effect of bending moments normally induced by misalignment.
3.5.1 Pressure test on the converged model
This section discusses the convergence study that had been carried out on the
numerical model, based on a constant pressure of 10 bar, and the results are summarised
in Table 3.1. The convergence of stress and strain values at the notch root was achieved
when the number of elements had reached 14,504.
Table 3.1: The convergence study at the notch root - constant pressure of 10 bar
No of
Elements
Hoop Stress
( x ) - MPa
Axial Stress
( y ) - MPa
71
Hoop Strain
( x ) x 10 -5
Axial Strain
( y ) x 10 -5
1,620 20.756 11.580 8.270 2.560
4,170 20.183 11.367 8.035 2.550
8,840 20.241 11.552 8.028 2.623
12,558 20.261 11.635 8.027 2.652
14,504 20.257 11.638 8.026 2.654
After identifying the number of elements through the linear study, the pressure
of 10 bar increments was applied on the inside surface of the model up to 50 bar.
Results are summarized in Table 3.2 and plotted in Figures 3.12 and 3.13.