Resumo em Inglês:

Abstract Compared with central penetration, the eccentric penetration of jet into a liquid-filled composite armor (LCA) shows a more obvious lateral displacement due to the asymmetric impact by the shock wave and liquid radial reflux. Based on this characteristic, the reaming process in the liquid layer during the shaped charge jet (SCJ) penetrates into the strongly-constrained liquid-filled composite armor (SLCA) eccentrically, the interference process of jet is subjected to the asymmetric impact by the shock wave and liquid radial reflux, and the lateral movement process of the SCJ under lateral force loading is analyzed to study the influence of SLCA on the stability of incoming SCJ during eccentric penetration. Theoretical and X-ray experimental results show that when the eccentricity distance is [0 mm, 12 mm], the severely disturbed velocity range and total disturbed velocity range of the SCJ increase with the increase of the eccentricity distance, while the maximum lateral displacement of the SCJ decreases slightly with the increase of the eccentricity distance at [1 mm, 12 mm].

Resumo em Inglês:

Abstract The fundamental difference in the solution of solids and fluids relies on the respective constitutive laws. Based on the Rivlin-Saunders-Düster-Hartmann hyperelastic model and using the Flory’s strain decomposition, we present a new total Lagrangian viscoelastic constitutive model for both Kelvin-Voigt viscoelastic solids and free-surface compressive viscous isothermal fluids. A dissipative viscous virtual work is written as a function of the time rate of isochoric invariants and its relation with the viscous stress is derived. Local time derivatives are solved by backward finite difference, allowing a consistent tangent viscoelastic constitutive tensor. The virtual work principle is used to write the weak equilibrium equation and its position-based finite element counterpart. Dynamic time integration is carried out by the Newmark β method and the Newton-Raphson procedure is used to solve time steps. The formulation is validated against experimental and numerical literature results revealing good precision. Additional examples are shown in order to demonstrate the applicability and future possibilities of the technique.

Resumo em Inglês:

Abstract In this paper, the ultra-high drop hammer impact test system is adopted for the vertical impact experiment on six SFSRCBs with steel fiber volume fraction of 2.0% and build the relevant numerical model. The research variables mainly include impact energy, impact mass and cumulative impact mode. The results show that, under a single equal energy impact, with the increase of the impact speed, the crack distribution of the specimen gradually tends to the mid-span local position. Compared with the impact mass, the impact speed has a greater effect on the failure mode, deformation resistance and deformation recovery ability of SFSRCBs. When the total cumulative impact energy is the same as the single impact energy, then the overall damage of the specimen caused by high-mass low-velocity cumulative impact is less significant than that caused by low-mass high-velocity cumulative impact. Combined with the finite element analysis, the calculation formula of the maximum deflection of SFSRCB under impact load is obtained. Finally, the calculation method of the impact damage evaluation factor of SFSRCBs is proposed.

Resumo em Inglês:

Abstract In this paper, LS-dyna software was used to simulate the charging process of cylindrical shell when EFP has different angles, and some interesting phenomena and laws were found. Cylindrical elastic wave σr was generated when the cylindrical shell was impacted by EFP. The cylindrical elastic wave σr was correlated with the time required for the cylindrical shell charge to be successfully detonated. When the EFP warhead penetration Angle θ ranges from 0° to 10°, the σr increases linearly with (cosθ)-1/2. With the increase of θ, the tangential velocity vy had an obvious effect on the impact of EFP on the cylindrical shell, and the linear relationship between the elastic wave σr and (cosθ)-1/2 does not change. When the θ was greater than 45°, EFP could not successfully impact and detonate the cylindrical shell charge. The EFP velocity was measured by velocity measurement method with an error of 1.3%. The experimental results have strong similarity with the simulation results, indicating that the parameters of the numerical simulation model have good reliability.

Resumo em Inglês:

Abstract Fragmentation is the main energy dissipation form of foam concrete under explosion loading. To characterize the energy dissipation of foam concrete fragmentation quantitatively, explosion loading experiments of foam concrete plates under different stand-offs and plate thicknesses were carried out. The statistical characteristics of fragments and the energy dissipation law of foam concrete plate fragmentation were studied using image processing, fracture mechanics theory and fractal theory. An engineering calculation model of fragmentation fractal dimension and energy dissipation density of foam concrete plates were established. Results show that: the fragmentation of foam concrete plates under different explosion conditions is a fractal in the statistical sense. With the increase in stand-off and plate thickness, the fragment size of foam concrete plates increases, and the fragmentation fractal dimension decreases linearly. The linear relationship between the energy dissipation density and the fragmentation fractal dimension of foam concrete are expressed as Df=0.0165ω+1.053.