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To obtain the dynamic response of the launching site under the different binding states of base and surface layers, an interlayer binding mathematical model of base and surface layers is established based on bilinear cohesion constitutive of cohesive element. A cohesion mathematical model under different binding states of base and surface layers is established by introducing the initial damage variable and using the strain equivalence hypothesis. A numerical model of launching site under different binding states of base and surface layer is built based on the numerical model with interlayer effect, the distribution and evolution of damage on base-surface layer interface of the launching site below the bottom of launch canister are analyzed, and the dynamic response of the launching site under different binding states of base and surface layer is researched. The result shows that, when the base-surface layer binding state remains constant, the interface damage is the most serious in the base layer where the boundary is forced by the load applied by the bottom of the launch canister, and the interface damage of the base layer firstly increases and then decreases along the radius direction of the load area. When the binding state of base and surface layer gets worse,the interface damage of the base layer is invariant in the middle and decrease on both sides along the radius direction of the load area, the vertical and horizontal displacements of the launching site surface get larger in different degrees, and the maximum stresses of the surface and base layers center-bottom points get smaller. [ABSTRACT FROM AUTHOR]

To study the influence of annular cavity of gas-ejection launcher on secondary combustion, RNG k-ε turbulence model, finite-rate/dissipation model and dynamic mesh update method are adopted to establish a secondary combustion model of initial cavity, in which the movement of rear cover is considered. Compared with experimental result of ejection launcher without annular cavity, the variation in fluid structure, ejection interior ballistics and variation in load are studied for the initial cavity with/without annular cavity and the initial cavity with different opening directions. The mechanism of that annular cavity reduces the secondary combustion impact is analyzed. Results show that, from the point view of fluid structure, an annular cavity can is added to change the direction of gas diffusion and decrease the area between gas and air. The backflow region with annular cavity can decrease the pressure peak caused by secondary combustion. From the point view of interior ballistics, the acceleration of missile in which the annular cavity opening is formed upwardly changes gently, the velocity out of tube is reduced by 5.9%, and the time out of tube is delayed by 4.5% [ABSTRACT FROM AUTHOR]