Material properties of the sonar dome window.MaterialYoung’s modulus (N/mm2)Poison ratioGRP13,0000.35Rubber (NBR)500.45Full-size tableTable optionsView in workspaceDownload as CSV
4.2. Results for Case 1
The stress distribution on the sonar window under the hydrostatic pressure at anchoring M-344 shown in Fig. 13. The maximum stress of 13.2 MPa occurred at the edge of the GRP flange and widow connection. When the valve was closed, the hydrostatic pressure was 5.4 m water head, considering the inner and outer water height of the sonar window (H = 5.7 m, A = 0.3 m, h = 1 m in Fig. 8). When the flooding valve was open, there was no hydrostatic pressure on the surface of the sonar window.
Fig. 13. Von Misses stress distribution under the hydrostatic pressure.Figure optionsDownload full-size imageDownload as PowerPoint slide
As buckling can occur under a hydrostatic load, buckling analysis was also performed using MSC Nastran (sol. 105), as shown in Fig. 14. Fig. 14 shows the first and second buckling mode, as well as the third and fourth mode of the sonar window, under hydrostatic pressure. The results showed that buckling can occur in the first and second mode when the hydrostatic pressure is more than 10.2 m of water head and that ecotones can occur in the third and fourth mode when the hydrostatic pressure is 11.3 m of water head. The safety factor was 1.766 for the 5.4 m water head condition in the first buckling mode, as shown in Table 3.