Revista Militar de Ciência e Tecnologia

A study of densification and morphology in functionally graded materials of alumina ceramics doped with niobium oxide and silicon dioxide.

2025-10-31T13:42:01+00:00

Advanced Ceramic have several applications, among them we could highlight ballistic protection. This usage is mostly due to its mechanical strength and low weight. Alumina (Al₂O₃), given its characteristics such as easy to obtain and low production cost, represents one of the most researched and used for this purpose of use. However, every material has its own limitation of use, such as low density and bad strength when used without doping. Therefore, solutions have been researched to increase alumina density and improve microstructural to promote better ballistic performance. Even if the homogeneous material get better results, still there is some room for improvement on trying something new. One type of material which has been showing good development is Functionally Graded Materials that could promote a change in characteristics in the same material or that causes a material to behave similar to a ballistic system of several distinct layers, but with the advantage of having no stress concentrators as composites. Thus, this work aims to study the densification of Functionally Graded materials in conventional sintering and to observe microstructure characteristic of the layers in a Scanning Electron Microscope (SEM).

A review of materials to be used in stand alone ballistic plates as per the Joint Operational Requirements of the Ministry of Defense

2025-10-31T13:42:01+00:00

The development of ballistic materials resistant to new threats is a topic of great concern on the global stage. In 2018, the Ministry of Defense established the Joint Operational Requirements (JOR) for the Armed Forces’ ballistic protection materials. Until now, the Defense Industrial Base has not presented a ballistic solution for some of the calibers surveyed. In this scenario, equipment has been chosen that allow greater mobility for the user combined with protection against calibers with greater kinetic energy. Thus, this article aims to present a review of materials to compose a Multilayer Armor System (MAS) for stand alone plates for assault vests, in addition to presenting the standards and conditions for evaluating ballistic materials adopted in the context of domestically and internationally.

Evaluation of the mechanical properties of AA 5052 and AA 5050C aluminum alloy rolled sheets

2025-10-31T13:42:01+00:00

This study was conducted on AA 5052 sheets that had been produced by direct casting and AA 5050C sheets that had been produced by twin roll casting to microstructurally and mechanically characterize these alloys and evaluate their dynamic aging occurrence as a function of the strain rate applied in uniaxial tensile tests. In general, AA 5052 alloy showed higher strength values and lower ductility. Analysis of the aspect of tensile curves showed serrations in both alloys, indicating rapid and successive stresses variations in the plastic deformation region for both alloys, suggesting dynamic aging occurrence and how this effect is more pronounced at lower displacement speed. The frequency and magnitude of the decrease stress can be associated with the distinct Mg content of the alloys, being smaller in the AA 5050C.

Ballistic resistance and microwave absorbing properties of a composite made of aramid fabric impregnated with polyethylene glycol and hematite nanoparticles

2025-10-31T13:42:01+00:00

A resistência balística e a absorção de micro-ondas de um composto de tecido de aramida impregnado com polietilenoglicol e nanopartículas de hematita foram investigadas para diferentes concentrações de hematita entre 0 e 17% em peso. Foram identificados diferentes mecanismos de dano e de absorção de energia durante o impacto balístico: formação de cone na face posterior do alvo, falha de tração dos fios primários e deformação dos fios secundários. Em termos de absorção de energia, os melhores resultados foram obtidos com hematita a 7% em peso, enquanto a menor profundidade de penetração (DOP) foi observada em um composto com hematita a 9% em peso. Uma imagem de microscópio eletrônico de varredura (SEM) do compósito com 7% de hematita após o teste balístico mostrou que o principal mecanismo de absorção de energia foi a deformação dos fios secundários. A absorção de micro-ondas foi medida usando a técnica de guia de ondas na faixa de frequência de 8 a 12 GHz. Os resultados mostraram que a perda dielétrica ɛ“/ɛ’ é máxima para uma concentração de 3% de hematita, enquanto a perda magnética µ”/µ’ é máxima para uma concentração de 11% em peso de hematita. Um compromisso razoável entre a resistência balística e a absorção de micro-ondas parece ser um composto com 7 wt% de hematita.

Influence of surface treatment on the primary stability of osseointegrated dental implants quantified with a strain gauge

2025-10-31T13:42:01+00:00

There are several hypotheses to explain the failures of osseointegrated titanium dental implants. Some possible explanations are the alterations in the mechanical properties of the maxillary bones, the surgical technique employed with excessive torques, the inadequate shape of the implants, and the deficient treatment of the surface of the implants. This work aims to measure the strain in the bone, quantify the insertion torque, and analyze the influence of surface treatment on the primary stability of dental implants. Extensometry tests were performed using strain gauges, and the insertion torque of the implants in synthetic polyurethane bone with a density of 30 PCF (0.48 g/cm³) was determined. The tests quantified the deformations in the synthetic bone and the maximum insertion torques of implants with the surface treated with double acid etching and without treatment (machined). The results showed that implants without surface treatment induce greater bone deformation, require lower insertion torque, have lower primary stability, and, in some essays, induce microcracks formation in the bone during insertion. Implants with an acid-treated surface perform better.

Editorial

2025-10-31T13:47:33+00:00

The Impact of Assigning Weights to Semantic Resources on the Identification of Criminal Suspects on Social Media

2025-10-31T13:42:01+00:00

The identification of criminal suspects on social media has been a topic of great relevance in the analysis of this type of media. Most of the time, the methods that seek to identify these suspects use textual data made available by people on these networks (e.g. messages, comments, among others). To analyze the texts, these methods often use semantic resources such as controlled vocabularies or even simple sets composed of terms, according to the domain in question (e.g. terrorism, pedophilia, among others). The mention of one or more of these terms can raise suspicions about the people who have used them. However, some terms raise more suspicion than others. Therefore, this work seeks to investigate the impact of differentiating the level of dangerousness of the terms used by a method for identifying criminal suspects on social media and whether this can lead to better results in identifying suspects. The results obtained through experiments in the domain of pedophilia showed that differentiating the level of dangerousness of the terms provided better results in 82.5% of the experiments carried out.

Estimation of target azimuth based on multiple beamforming processes in a phased array radar system

2025-10-31T13:42:02+00:00

This work investigates the combination of the Maximum Likelihood (ML) approach with a reduced number of fixed beam steerings in order to estimate target azimuth in a surveillance radar-based system equipped with sensor array. Simulation-based performance results of the estimator using only two fixed beams are presented. It is verified that there is a great advantage of the ML solution compared to an usual monopulse estimator, which employs the same number of beams. Additional results show that greater performance gains can be obtained with the investigated ML approach using only one additional beam.