Issue 32

I. Telichev, Frattura ed Integrità Strutturale, 32 (2015) 24-34; DOI: 10.3221/IGF-ESIS.32.03 26 The present paper is focused on the engineering methodology which allows determining the border between the simple perforation and catastrophic fracture of impact-damaged pressurized modules and pressure vessels onboard spacecraft. This methodology is viewed as a key element in the survivability-driven spacecraft design procedure providing that under no circumstances will the “unzipping” occur. Addressing this problem will not only improve the survivability of spacecraft itself but also will provide the mitigation effect since each satellite break-up causes not only the loss of space assets but the considerable addition to the orbital debris population. M ODELING OF IMPACT DAMAGE xperimental studies have shown that the impact damage has the form of a hole surrounded by a zone of the crack- like defects (Fig. 2a, b, c). For the case of both shield and pressure wall perforation the impact damage varies from the petal hole (Fig. 2a) to the “cookie-cutter hole” (Fig. 2b). The perforation of the unshielded wall is accompanied by a zone of spall cracks adjacent to the impact hole as shown in Fig. 2c. For further analysis it suggested to model the cracked area around the penetrated hole by two radial cracks emanating from the rim of the hole perpendicularly to the applied load. The diameter of the model hole is equal to the diameter of the impact hole ( D hole ), while the length of the fictitious radial cracks is bounded by a damage zone ( D crack ). In cylindrical pressurized structure these two radial cracks are set to be normal to the hoop stress, i.e. along the expected fracture path (Fig. 2d). Figure 2 : Modeling the impact holes: a) petal hole; b) “cookie-cutter hole”; c) hole with adjacent spall cracks; d) model of impact hole. Figure 3 : Snapshot of the evolution of the stress field after the hole was instantly formed in the loaded plate The penetration process lasts for a matter of microseconds and this process is essentially dynamic. After the appearance of an impact hole in the pre-loaded plate, the field of stress distribution around this hole does not change immediately. This transition process flows as the stress wave travels away from rim of hole. The evolution of the stress field near the hole in the perforated plate were evaluated explicitly using the Autodyn® code (Fig. 3). The obtained results are consistent E