Narrow Results

To improve the atomic oxygen (AO) erosion resistance of the polyimide (PI) maretials, cage-shaped poly-γ-aminopropylsiloxane (NPOSS) was synthesized from γ-aminopropyltriethoxysilane through the control of hydrolytic condensation conditions. Poly-γ-aminopropylsiloxane/methylphenylsilicone (NPOSS/MPS) hybrid films were prepared on PI samples. The physics and chemistry properties of the hybrid films surface was analyzed after exposure to AO flux in a ground AO simulated facility. The results showed that: NPOSS gathered to the spherical shapes and uniformly distributed in films, SiO₂ layer formed on the films surface after explorer and prevented the further AO erosion, mass loss and erosion rate of samples was dramatically decreased, AO erosion resistance had been increased and it could be further enhanced with the increase of NPOSS content.

In this work, the cavitation water jet technique was used to clean the inner walls of oil pipes after tertiary oil recovery. The surface morphology, depth of impinging pits, and corrosion resistance of aluminum samples after impingement with the cavitation water jet were examined using scanning electron microscopy (SEM), 3D microscopy, and an electrochemical workstation. When the inlet pressure was higher than 3MPa, the number of cavitation bubbles generated by the cavitation nozzle increased with an increase in inlet pressure. Moreover, the cleaning effect that the cavitation water jet had on the aluminum samples was higher than that of general water jet technology. There were no obvious changes to the surface of the aluminum samples when the inlet pressure was decreased to 13MPa. Meanwhile, the mass loss of aluminum samples also increased. However, the internal corrosion resistance of the pipe wall after impact was relatively low. These results indicate that the impinging efficiency of the cavitation water jet was obviously enhanced and the degree of damage to the oil pipe wall was low at an inlet pressure of 15MPa. The best target distance was 8–12mm, and at this point, the jet flushing effect was the best. Moreover, the jet velocity at the outlet cavity was 184m/s, and the jet strike area was 250mm².

A projectile may be deformed and eroded due to the high pressure generated by hypervelocity penetration, which makes it difficult to describe the penetration mechanism for protection engineering by existing theories at such high velocities. To analyze the penetration depth of concrete-like targets subjected to hypervelocity impact by kinetic energy weapons, experiments with ogive-nosed steel projectiles penetrating mortar targets are conducted, where the average uniaxial compressive strength of the mortar targets is 41.8MPa and the impact velocities range from 1225m/s to 2392m/s. The experimental results show that the crater diameter and crater depth have a linear relationship with the striking velocity. The depth of penetration (DOP) increases linearly first and then decreases sharply and increases slowly again. Three penetration regimes are observed in turn with increasing velocity, i.e. rigid projectile penetration, abrasive projectile penetration and semifluid projectile penetration. Furthermore, based on a study of the dynamic compression behavior and penetration resistance function of concrete, a hydroelastoplastic-frictional penetration model is established. The velocity range is divided into solid penetration, semifluid penetration and fluid penetration, which correspond to $0\le M_a^{\prime }\le 1$, $1\le M_a^{\prime }\le 3$ and $M_a^{\prime }\ge 3$, respectively. Then, the rigid and abrasive projectile penetration models, which consider the projectile mass loss, are verified by the present test data. Finally, the semifluid projectile penetration model is evaluated with the existing test data. These results can provide support for research on the damage effect of hypervelocity kinetic energy weapons and the design of underground strategic protection engineering.