Resumo em Inglês:

Abstract This research explores the dynamic responses of reinforced concrete (RC) slabs under high-velocity impacts. The study utilizes advanced numerical simulations to investigate the effects of varied impact loading and slab depths, unveiling complex rate-dependent behaviors (i.e., impact forces, reactions, accelerations, and displacements) across a diverse range of velocities. The alignment of simulation results with experimental data validates the robustness and accuracy of the employed approach. Additionally, an analytical model predicting the load-carrying capacity and deflection of these slabs under high-velocity loads is proposed. The results indicated that higher loading rates correlate with increased forces and damage until perforation. Analytical models exhibit strong performance within a ±10% error margin, and response surface analysis quantifies the impactor velocity's influence on load for a constant thickness. Overall, this investigation sheds light on the dynamic complexities of RC slabs subjected to high-velocity impacts, providing valuable insights for structural design considerations.

Resumo em Inglês:

Abstract In urban combat, sub-millimeter inert metal powder is used to replace fragments in explosive bombs, which can effectively reduce collateral damage. In order to investigate the damage effect of high-speed metal particles on the human body, a particle ring filled with a charge was designed to create an explosion-driven particle cloud for the penetration ballistic gelatin. The particle ring was made of polytetrafluoroethylene (PTFE) and sub-millimeter tungsten powder. The dispersion properties of the particle cloud driven by the explosion were studied with high-speed photography and ballistic gelatin. Furthermore, the numerical simulation models of particle-penetrating gelatin based on the experimental results were established with the finite element method. The influences of the particle size and velocity on the penetration depth and cavity diameter was obtained. The relationship between the critical interference distance of the cavity and the distance between particles was determined. This paper provides references and theoretical support for the design of low collateral damage ammunition based on inert metal powder.

Resumo em Inglês:

Abstract Liquid composite armor has demonstrated excellent performance in protecting against shaped charge jets. Currently, most existing theoretical calculation models for the velocity range of the disturbed jet approximate the cone angle of the shockwave front as the Mach angle. However, indiscriminately equating the cone angle of the shockwave front with the Mach angle can lead to significant errors in the calculated velocity range of the disturbed jet. To address this issue, this study focuses on investigating the variation of the cone angle of the shockwave front within the liquid composite protective structure. Firstly, a dimensional analysis was conducted to determine the functional relationship between the cone angle of the shockwave front and relevant parameters. Then, the process of jet penetrating liquid composite protective structure was simulated by Autodyn. The results demonstrated that the normalized cone angle solely depends on the normalized diameter within the critical angle. By fitting the simulation data, the formula for calculating the cone angle of the shockwave front was derived.

Resumo em Inglês:

Abstract The detonation of conventional munitions due to accidents or hostile actions causes urban destruction and loss of life, underscoring the need for improved safety measures. This study addresses the scarcity of research in munitions safety by investigating the threat of small and medium munitions. Experimental setups using 50mm shaped charges were developed and simulated with ANSYS AUTODYN, featuring JH-2 explosive and oxygen free high conductivity copper liner. Aluminum buffer plates were added to align jet energy levels with small and medium munitions' requirements. Safety assessments of JH-2 explosive against standard charges utilized φ45x40mm JH-2 targets covered with steel. Numerical simulations employed the Lee-Tarver ignition and growth model, comparing JH-2 explosive response with insensitive explosives like LX-17 and TATB. Results showed JH-2's failure in experimental tests, corroborated by simulations, while TATB and LX-17 remained stable. This study advocates for the adoption of cost-effective, insensitive explosives in next generation weaponry to mitigate unintentional detonations.

Resumo em Inglês:

Abstract The study aims to enhance the bonding strength in reinforced concrete using a novel Auxetic Tubular Deformed Rebar (ATDR). A high-resolution non-linear finite element model was developed to perform numerical analysis of pull-out tests (PoT). Two sets of numerical simulations were conducted: one to replicate the concrete behavior under compression and tension tests, and the other for PoT, validated with experimental and numerical data. Numerical tests utilized a microplane model with plasticity–damage, regularized by an implicit gradient. Auxetic geometry involves adding ellipsoidal orifices to the rebar surface. Comparing the behavior of ATDR with the conventional rebar, we observed an increase in the negative value of Poisson's ratio, resulting in higher normal and shear forces, enhancing adherence. This study presents the first comprehensive simulation of Auxetic Metamaterial Rebar in concrete, offering a promising approach to enhance bond strength. Further research, both numerical and experimental, is essential to assess Auxetic Reinforcement's mechanical behavior in diverse structural elements and load scenarios.

Resumo em Inglês:

Abstract This paper introduces the Julia programming language as a dynamic, cost-effective, and efficient framework for implementing structural analysis packages. To achieve this, the finite element method was implemented for plane frames addressing the elastic instability problem through the Finite Element Method (FEM). Julia is a language open source, multiplatform, high-level and high-performance for technical and scientific computing, its compiler allows you to achieve speeds comparable to languages such as C and FORTRAN, but with more productive development dynamics due to its programming flexibility. Benchmarks between Julia and MATLAB are employed to discuss the processing costs, the programming techniques and paradigms used for computational performance. The results demonstrate that Julia performed the same analysis as the language used for comparison in 88.40% of the time, in addition to the fact that in loops comparisons case it reached 41.7% of the time for iteration, confirming its significant potential as a development tool of computational packages for structural analysis and scientific computing in general.