Snapping shrimp produces a high-speed jet through the rapid closure of the snapper claw, which stimulates the formation of cavitation bubbles of various shapes. In order to explore the fast motion characteristics of snapper claw, the formation and change process of cavitation, and the physical principles underlying the biological phenomena, the equivalent model of snapper claw was constructed through CT scanning technology. A high-speed camera was used to capture the claw’s motion characteristics, thereby simulating the production of cavitation bubbles by snapping shrimp. The results show that the rotation speeds of different species of snapping shrimps are different, as well as their motion characteristics. Cavitation is formed by the interaction of the pressure drop caused by the vortex at the nozzle with the inertia of the liquid inside the socket. Under the influence of the jet, the shapes of bubbles change from ring to cone, and eventually collapse into bubble clouds.

Breechblock operating force is one of the key test parameters of the shock test bed for gun breechblock system. With the design principle determined, the dynamics principle model of the shock test bed is established based on the virtual prototype technology. The kinetic energy theorem is used to calculate the minimum theoretical force F, a standard value for shock test bed to open breechblock. As both the mass of breechblock operating cam and the breechblock operating distance are fixed, the simulation experiment is performed based on the principle model when the breechblock operating force is F.. The results show that the test bed fails to open breechblock under the working condition for energy loss during the impact. By the research, it is better to grasp the dynamics characteristics of test bed before the physical entity experiments, which is benefit to choose a suitable breechblock operating force.

Abstract. In order to test the dynamic characteristics of the shock test bed for gun breechblock system expediently, the dynamic model was established based on the virtual prototype technology. The three-dimensional solid model of each part was established and assembled by software Pro/Engineer. Then the whole model was imported into the dynamic software MSC.ADAMS through the interface, Mechanism/Pro, between the two software. Then the constraints, contacts or spring force between each two parts were added in the model according to the relation in practice. The force outside was imposed on the bearing part. After that, the virtual prototype model was established. With the model, simulation was processed and the dynamic characteristics of the parts of the shock test bed were tested under different conditions. The test results show that the model is tallies with the physical prototype and can be used to analyze the dynamic characteristics of the shock test bed parts.

By studying effect of different duty cycles on tungsten-cobalt film to improve its performances, tungsten-cobalt films were prepared on the surface of PCrNi3MoVA steel by electrodeposition under different duty cycles. The results show that grain size increases with increasing duty cycle but tungsten content, microhardness, film-based bond strength and TC (100) increase first and then decrease with increasing duty cycle. When the duty cycle is 30%, tungsten-cobalt films with highest tungsten content (43.37%), grain size (12.3 nm) and largest TC (100) (0.845) have highest microhardness (7.1 GPa) and strongest film-base bond (24 N), which results in lowest friction coefficient (0.31) and smallest wear rate (2 © 10 ¹5 mm 3 N ¹1 m ¹1 ) that is only 28.57% for the tungsten-cobalt film prepared under 100% duty cycle.

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