PSI - Issue 71

V. Thondamon et al. / Procedia Structural Integrity 71 (2025) 226–232

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forces of 90 kN and 105 kN were used for both 89 mm and 142 mm diameter indenters. Table 2 shows the summary of cases considered for re-rounding study. For re-rounding studies, dent depths of 35.6 mm and 44.5 mm (10% and 12.5% of the outer diameter respectively) were used for both 89 mm and 142 mm diameter indenters. Table 1. Summary of cases used for dent formation study

Pipe outer diameter (mm)

Pipe thickness (mm)

Indenter diameter (mm)

Indentation force (kN)

Internal pressure at indentation (MPa)

Case ID

DF1 DF2 DF3 DF4

356 356 356 356

7.8 7.8 7.8 7.8

89 89

90

0 0 0 0

105

142 142

90

105

Table 2. Summary of cases used for re-rounding study

Pipe outer diameter (mm)

Pipe thickness (mm)

Indenter diameter (mm)

Internal pressure at indentation (MPa)

Case ID

Dent depth (mm)

RR1 RR2 RR3 RR4 RR5 RR6 RR7 RR8

356 356 356 356 356 356 356 356

7.8 7.8 7.8 7.8 7.8 7.8 7.8 7.8

89 89

35.6 44.5 35.6 44.5 35.6 44.5 35.6 44.5

0 0 0 0 9 9 9 9

142 142

89 89

142 142

Fig. 1. Typical indenter position and support of pipe in FE model

Re-rounding studies were performed for two conditions. RR1 to RR4 were studied under commissioning condition and RR5 to RR8 were studied under in-service conditions.

3.1 Commissioning condition

In the commissioning condition, firstly, dents were imparted on the pipes using rigid indenter and the indenter is removed. Dent depths at various steps are measured. Strain variation at different locations in the longitudinal direction and circumferential direction of the pipe are plotted and studied to understand the re-rounding behaviour of dent during commissioning condition.