PSI - Issue 71

Sarath Chandran Nair S. et al. / Procedia Structural Integrity 71 (2025) 340–347

346

a

b

Fig. 5: Stresses (MPa) on Polyimide pipe for deflection test condition (a) Room Temperature; (b) LN2 temperature Stress to be simulated is finalised by FE analysis as shown in Fig. 6. Load predicted for simulating the required stress varies from 85.6 to 128.4 kgf for room temperature deflection test, whereas load varies 236.5 to 354.7 kgf for LN2 temperature. This variation in load is due to the dispersion in Young’s modulus of the polyimide material. Deflections in the loading direction and perpendicular to the loading direction are predicted as 52.6 mm and 23. 0mm respectively for room temperature, whereas 9.9 mm and 27.3mm for LN2 temperature. 7.2 Deflection test Polyimide pipelines are undergone deflection test for its flight acceptance. Compared the predicted and achieved load and deflections for all the polyimide pipes. Comparison of the defection predicted and obtained from the test for a typical polyimide line is shown in Fig. 6.

a

b

Fig. 6: Comparison of deflections predicted and achieved (a) Room temperature test; (b) LN2 temperature test

Predicted and achieved deflections and load for the same polyimide pipe are given in table 4 for room temperature and LN2 temperature tests.

Table 4: Deflection test parameters of polyimide line Deflection Test Parameters Room temperature test

LN2 temperature test

Prediction

Test 30.3 53.4

Prediction

Test 27.5 10.3

Displacement, mm Dx 23.0

27.3

Dy 52.6

9.9

Load, kgf 236.5 to 354.7 303.2 Required deflections are met within the load predicted through FE analysis for all the polyimide pipes. All the polyimide pipes have undergone post-test NDT and visual inspection. No observations such as delamination, bending, 85.6 to 128.4 114.5