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This is Fig. 17 from the 2007 axialcomp paper. This slide shows the linear general buckling mode from the STAGS model.
In contrast to the model shown in the prevous slide in which both stringers and rings are smeared, in this STAGS model only the stringers are smeared.
The internal T-shaped rings are modeled as shell units, 2 shell units per ring: Shell unit (a) for the ring web and Shell unit (b) for the ring outstanding flange. One internal ring is partly visible at the left-most edge of the model.
Shown here is the STAGS prediction for Case 2, Table 4: no Koiter, yes change imperfection, ICONSV = -1; Compare with the previous slide.
Shown here is STAGS Mode no. 1, load factor, pcr=1.9017; PANDA2 predicts 1.890. The linear buckling mode agrees with that from PANDA2: (m,n)=(4,6) halfwaves over 180 deg. See Part 1, Run 2 in Table 9 of the paper.
This STAGS model and the STAGS model in the previous slide are used to obtain good approximations of the general buckling mode shape and load factor (eigenvalue) for two reasons:
1. Determine what circumferential sector to use for more refined models (60 degrees is good in this case), and
2. obtain a good estimate of the initial eigenvalue “shift” to use in more refined STAGS models.
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