ABSTRACT In the automotive sector, aluminum alloys have stood out for their attractive combination of strength-to-weight ratio, among other characteristics. The 5XXX series alloys mechanical properties are related to their composition and the manufacturing process used, gaining most of their mechanical strength through cold deformation processes. One of the requirements to optimize mechanical forming operations is the microstructure and texture control. In this study, AA 5052 and AA 5050C alloys, produced by Direct Chill (DC) casting and Twin Roll Caster (TRC), respectively, underwent mechanical characterization through tensile testing (with specimens extracted at 0, 45, and 90° from the rolling direction); and microstructural and texture characterization across the thickness of the sheets. Alumina (Al2O3) inclusions and intermetallic precipitates of Al3Fe were detected along the metallic matrix of both alloys, exhibiting components of copper (112)[ 1 11 ¯], brass {110}<112>, cube (001)[ 0 10 ¯], and Goss {110}<001> throughout the thickness. AA 5052 alloy showed higher planar and normal anisotropy values than AA 5050C alloy, as well as mechanical properties measured in uniaxial tension. sector strengthtoweight weight ratio characteristics XXX used processes control study 505 C DC (DC TRC, TRC , (TRC) respectively with 45 90 direction direction) sheets Al2O3 AlO Al O (Al2O3 AlFe Fe 112 (112) ¯, ¯ ¯] 110<112>, 110112 110 <112>, {110}<112> 001 (001) 110<001> 110001 <001> {110}<001 tension 50 (TRC 4 9 Al2O (Al2O (112 110<112> 11011 <112> {110}<112 00 (001 110<001 11000 <001 {110}<00 5 (11 110<112 1101 <112 {110}<11 (00 110<00 1100 <00 {110}<0 (1 110<11 <11 {110}<1 (0 110<0 <0 {110}< ( 110<1 <1 110< < {110} {110 {11 {1 {

RESUMO No setor automotivo as ligas de alumínio têm se destacado por sua atraente combinação entre resistência/peso, entre outras características. As ligas da série 5XXX tem seu ganho de resistência mecânica através de processos de deformação a frio, e as propriedades mecânicas das ligas de alumínio estão diretamente relacionadas à sua composição e ao processo de fabricação utilizado em sua manufatura. Um dos requisitos para otimizar as operações de conformação mecânica é o controle da microestrutura e textura. Neste trabalho, as ligas AA 5052 e AA 5050C, produzidas por Fundição Direta (Direct Chill – DC), e Fundição Contínua de Chapas (Twin Roll Caster – TRC), respectivamente, passaram por caracterização mecânica via ensaio de tração (com corpos de provas extraídos a 0, 45 e 90° da direção de laminação) e caracterização estrutural e textura ao longo da espessura de chapas. Foram detectadas inclusões de alumina (Al2O3) e precipitados intermetálicos de Al3Fe juntos à matriz metálica e ambas as ligas apresentam as componentes cobre (112)[ 1 11 ¯], latão (“Brass”) {110}<112>, cubo (001)[ 0 10 ¯] e Goss {110}<001>, ao longo da espessura. A liga AA 5052 apresentou valores de coeficiente de anisotropia planar e normal superiores aos da liga AA 5050C, como também as propriedades mecânicas medidas em tração uniaxial. resistênciapeso peso resistência/peso características XXX frio manufatura trabalho 505 5050C C Direct DC, DC , DC) Twin TRC, TRC TRC) respectivamente com 4 90 laminação chapas Al2O3 AlO Al O (Al2O3 AlFe Fe 112 (112) ¯, ¯ Brass (“Brass” 110<112>, 110112 110 <112>, {110}<112> 001 (001) 110<001>, 110001 <001>, {110}<001> uniaxial 50 9 Al2O (Al2O (112 (“Brass 110<112> 11011 <112> {110}<112 00 (001 110<001> 11000 <001> {110}<001 5 (11 110<112 1101 <112 {110}<11 (00 110<001 1100 <001 {110}<00 (1 110<11 <11 {110}<1 (0 110<00 <00 {110}<0 ( 110<1 <1 {110}< 110<0 <0 110< < {110} {110 {11 {1 {

Resumen En el presente trabajo se estudiaron los efectos de forma y tamaño de los poros sobre las propiedades mecánicas de membranas de grafeno nanoporosas (GNP). Las simulaciones de dinámica molecular fueron ejecutadas para estudiar las respuestas mecánicas y estructurales bajo una tracción uniaxial. Los resultados de las curvas tensión-deformación de las membranas de GNP muestran un comportamiento lineal elástico para razones de deformacion pequeñas (<0.03) independiente de la dirección quiral. La anisotropía quiral (dirección armchair y zigzag) es notoria conforme se incrementa la deformación hasta el punto de fractura. Las membranas de GNP con poro hexagonal y rectangular presentan una mayor tensión de fractura (65 GPa y 81 GPa, respectivamente). Además, el módulo elástico de Young disminuye conforme se incrementa el tamaño del poro. Se espera que este estudio brinde aplicación práctica como filtros de membranas de alto rendimiento.

Abstract In this work, effects of shape and size of the pores on the mechanical properties of nanoporous graphene (NPG) membranes are studied. Molecular dynamics simulations were performed to study the mechanical and structural responses under uniaxial traction. The results of the stress-strain curves of NPG membranes show an elastic linear behavior for small strain (<0.03) independent of the chiral direction. The chiral anisotropy (armchair and zigzag direction) is notable as deformation increases to the point of fracture. The NPG membranes with hexagonal and rectangular pores present a higher fracture stress (65 GPa and 81 GPa, respectively). Furthermore, Young's elastic modulus decreases as pore size increases (porosity). This study is expected to provide practical application as high performance membrane filters.

In this paper we introduce an alternative method to determine the scale factor necessary to quantitatively compare the two coplanar components of the magnetization (components in the plane of the surface of the sample) of a film using the v-MOKE technique (vectorial-MOKE). The proposed method has the advantage of not needing the reorientation of the electromagnet generating the magnetic field, since, depending on the dimensions and weight thereof, this action can be difficult or directly impracticable. In this way, the experiment that allows for the acquisition of the two components in the plane of magnetization simultaneously, is executed without the need to modify the initial experimental arrangement (fixed assembly). As test samples, two 9 nm and 100 nm thick FePt films are used, presenting the first uniaxial anisotropy. All experiments were carried out at room temperature and using a MOKE system entirely built in the Surface Physics Group of the Instituto de Física del Litoral, allowing to simultaneously measure the two magnetization components coplanar with the surface sample (v-MOKE).

Se presenta un procedimiento alternativo al descripto en la bibliografía para determinar el factor de escala, necesario para comparar cuantitativamente dos de las componentes coplanares de la magnetización (componentes en el plano de la superficie de la muestra) de una película magnética mediante v-MOKE (vectorial-MOKE). El procedimiento propuesto posee la ventaja de no necesitar la reorientación del electroimán generador del campo magnetizante, ya que, dependiendo de las dimensiones y peso del mismo, esta acción puede resultar dificultosa o directamente impracticable. De esta manera, el experimento que permite adquirir las dos componentes en el plano de la magnetización de manera simultánea, se ejecuta sin necesidad de modificar la disposición experimental inicial (montaje fijo). Como muestras de prueba usamos dos películas de FePt de 9 nm y 100 nm de espesor, presentando la primera anisotropía uniaxial. Todos los experimentos se realizaron a temperatura ambiente y usando un sistema MOKE construido en el Grupo de Física de Superficies del IFIS-Litoral, el cual permite detectar dos componentes de la magnetización simultáneamente (v-MOKE).

Composite materials have been increasingly used in both researches and industries, given their wide range of innovative applications and configurations. High-performance hybrid fabric-reinforced plastics stand out in this sector. In the present research, an epoxy-based vinyl ester resin laminate reinforced with bidirectional hybrid fabric consisting of carbon and Kevlar fibers is developed. In order to determine its mechanical properties and damage mechanism considering the anisotropy and the presence of geometric discontinuity (circular hole), this research focused on both experimental and analytical aspect. Concerning to geometric discontinuity, in the vicinity of the hole (known as a stress concentration area), characteristic distances ao and do associated to ASC (Average Stress Criterion) and PSC (Point Stress Criterion) failure theories, respectively, were determined. All the study of the composite material mechanical behavior was conducted based on uniaxial tensile tests. Their results show higher losses in the mechanical properties of the hybrid laminate, with respect to the anisotropy and the presence of the central hole, mainly when the orientation of the Kevlar fibers coincides with the direction of the applied load.

ABSTRACT The magnetic Barkhausen noise (MBN) is a phenomenon that occurs in ferromagnetic materials when they are exposed to slowly varying magnetic fields, generating discrete jumps in their magnetization. These jumps are produced by the movement of the magnetic domain walls. They can be detected by a small coil allocated on the sample surface. The movement of the domain wall is regulated by the microstructure of the material (precipitates, grain size, residual stresses, etc.). Through this indirect way it is possible to characterize the material. In this work MBN measurements to study magnetic anisotropy induced by rolling processes and uniaxial strain tests are shown for ferritic stainless steels AISI: 409, 430 and 441A. The measurements were made at different strain percentages. The objective was to follow the changes in the MBN signals. The metallographic and hardness studies are presented. The results show a clear trend related with the direction of the principal stresses.

RESUMEN El ruido magnético Barkhausen (RMB) es un fenómeno que ocurre en materiales ferromagnéticos cuando se someten a campos magnéticos lentamente variables, generándose cambios en su magnetización, produciéndose “saltos” discretos. Estos saltos se generan por el movimiento de las paredes de los dominios magnéticos. Se detectan colocando una pequeña bobina sobre la superficie de la muestra. El movimiento de las paredes es regulado por la microestructura del material (precipitados, tamaño de grano, tensiones residuales, etc.). Es esta manera indirecta la que permite caracterizar al material. En este trabajo se presentan las mediciones del RMB para estudiar la anisotropía magnética, inducida por el proceso de laminación, y los cambios producidos por deformación plástica uniaxial en probetas de aceros inoxidables ferríticos AISI: 409, 430, 441A. Las mediciones se realizaron a diferentes porcentajes de deformación, con el fin de observar cómo cambian las características de las señales de RMB. Se presentan también los estudios métalográficos y de dureza. Los resultados muestran una clara tendencia en relación con la dirección de los esfuerzos principales.

Abstract Here we report on the effect of the ferromagnetic (FM) and antiferromagnetic (AF) films thicknesses on the exchange bias field in a FM/AF bilayer. For this, a series of NiFe(t NiFe)/NiO(t NiO) bilayers were grown by DC magnetron sputtering onto commercial Si(001) wafers. Magneto-optical hysteresis loops were used as probes to measure the exchange-bias field, and the coercivity field, as functions of the in-plane angle, φ H, and the films’ thicknesses, t NiFe and t NiO. The in-plane symmetry of the exchange field and coercivity display unidirectional and uniaxial anisotropies, with angular dependences different from the simple c o s φ H and c o s 2 φ H, respectively. These symmetries are intrinsically sensitive to the thickness of both NiFe and NiO layers. With respect to the FM layer thickness, the exchange bias and coercivity field follow the usual 1/t NiFe, while the dependence on the thickness of the AF layer is more complicated, and is characterized by a critical behavior.

Abstract . In this paper new empirical relationships are developed between uniaxial compressive strength and point load index Is(50) in anisotropic rocks, particularly in schists and shales. We have used data from 2015 point load tests and 229 uniaxial compressive strength tests performed in anisotropic rocks obtained during various stages of study of Paute-Cardenillo hydroelectric project, located in the eastern slopes of the northern Andes Cordillera (SE Ecuador). We have defined five anisotropic rocks types (schists and shales) for which the mean values of uniaxial compressive strength and point load index were obtained according to their orientation with respect to the planes of anisotropy. Finally, it is found that there is no direct relationship between uniaxial compressive strength and Is(50) so it is unreliable take traditional empirical linear regression models, which do not consider the effect of the planes of anisotropy in rock strength. Therefore, three new empirical relationships that estimate the uniaxial compressive strength from Is(50) in anisotropic rocks are proposed.

Resumen En este trabajo se establecen nuevas correlaciones empíricas entre la resistencia a compresión simple (RCS) y el índice de carga puntual Is(50) en rocas anisótropas, en particular en esquistos y pizarras. Se han empleado datos de 2015 ensayos de carga puntual y 229 ensayos de resistencia a compresión uniaxial realizados en rocas anisótropas obtenidos en las diferentes etapas de estudio del proyecto hidroeléctrico Paute-Cardenillo, localizado en las estribaciones orientales de la cordillera de los Andes septentrionales (SE Ecuador). Se han identificado cinco litotipos de rocas anisótropas (esquistos y pizarras) para los que se han obtenido los valores medios de resistencia a compresión simple y del índice de carga puntual en función de su orientación con respecto a los planos de anisotropía. Finalmente, se comprueba que no existe una relación directa entre RCS y Is(50) por lo que no es fiable adoptar los modelos empíricos tradicionales de regresión lineal, que no tienen en cuenta el efecto de los planos de anisotropía en la resistencia de la roca. Por lo tanto, se proponen tres nuevas relaciones empíricas que permiten estimar la RCS a partir del Is(50) en rocas anisótropas.

Reportamos evidencia experimental de polarización de intercambio entre una película ferromagnética (FM) de Fe4.6Co7(0.4)Si15B10 y una de NiO antiferromagnética (AF), depositadas sobre substratos de Si(001). Se obtuvieron las curvas de histéresis utilizando la técnica de Efecto Kerr Magnetoóptico de Superficie (SMOKE), y medimos el desplazamiento de las curvas y el campo coercitivo en función del ángulo acimutal, φH, y el espesor de la película FM, t. Las medidas revelan la presencia de anisotropías unidireccional y uniaxial, cuyas asimetrías corresponden a funciones complejas de cos(φH), y dependencia con el espesor proporcional a 1/t, típica de los efectos de interface.

We report on experimental evidence of exchange bias between the amorphous ferromagnetic (FM) Fe4.6Co70.4Si15B10 and an antiferromagnetic (AF) NiO film, grown onto single crystalline Si(001) wafers. Surface Magneto-optic Kerr Effect (SMOKE) has been used to measure the hysteresis loop shift, and coercivity, as functions of the azimuthal angle, φH, and the FM layer thickness, t. The measurements reveal the presence of induced unidirectional and uniaxial symmetries following a complex cosine dependence, and thickness dependence proportional to 1/t, typical of interfacial effects.

A Curva Limite de Conformação (CLC) é uma ferramenta muito útil, tanto na avaliação do comportamento plástico de chapas, quanto no projeto do ferramental para solucionar problemas de manufatura nas etapas de tentativas de erros-e-acertos. Esse trabalho apresenta o modelamento matemático da CLC com base em equações constitutivas em elasto-plasticidade e um critério de plasticidade anisotrópica. Demonstra-se, primeiro, que as deformações-limites no domínio de estiramento biaxial são controladas por um parâmetro material definido pela razão entre os limites de escoamento em deformação plana e tração biaxial simétrica. As previsões teóricas do modelo proposto apresentaram boa concordância com medidas experimentais disponíveis, na literatura, para uma chapa de alumínio A1100, e sugerem, igualmente, que os parâmetros do modelo de plasticidade, adotado para descrever anisotropia inicial de chapas metálicas, sejam identificados com bases em ensaios monotônicos de tração uniaxial e biaxial.

The Forming Limit Curve (FLC) is a very useful tool to assess either the plastic behavior of thin metallic sheets or the tooling design to solve manufacturing problems during the try-out steps. This work presents the mathematical modeling of the FLC based on elasto-plastic constitutive equations and anisotropic plasticity yield criterion. It is firstly demonstrated that the limit strains in the biaxial stretching domain are controlled by a material parameter defined by the ratio between the yield stresses in plane-strain tension and equibiaxial tension. The theoretical predictions of the proposed model showed a good agreement with the experimental data available in the literature for an aluminum A1100 sheet and also indicated that the parameters of plasticity model, adopted to describe the initial plastic anisotropy of metallic sheets, must be identified from monotonic uniaxial and biaxial tensile tests data.

In this paper, the boundary condition characteristic equation of the anisotropic-dielectric-loaded corrugated guide are developed. Dispersion curves of hybrid modes generated by the characteristic equation are presented and discussed. This paper also presents a technique to reduce the relative permittivity and create uniaxial anisotropy from isotropic homogeneous dielectric.

O presente trabalho tem por objetivo analisar a formação de bandas cisalhantes em chapas metálicas de aço baixo carbono (SAE 1006) submetidas à tração uniaxial. Essa verificação foi feita através de análise numérica utilizando o software Deform2D, bem como a realização dos testes físicos por meio de corpos-de-prova de tração entalhados com geometrias variadas. Foram levantadas a curva de fluxo e a anisotropia do material utilizado para a realização da simulação numérica. A partir dessa simulação, foram feitas análises da formação das bandas, utilizando-se vários passos em cada corpo-de-prova e, posteriormente, comparando essa mesma formação entre os corpos-de-prova com geometrias de entalhes diferentes. Por fim, foi verificado que, tanto a formação de bandas de cisalhamento, quanto às características da fratura no material estudado, estão diretamente relacionadas com a forma geométrica do entalhe.

The present study had as main purpose to analyze the formation of shear bands in metallic sheets of low-carbon steel (SAE 1006) submitted to uniaxial tension test. This verification has been made through numerical analysis using the software Deform2D, and the performance of physical tests with the tension's test specimen being notched with varied geometries. The flow curve and the anisotropy of the material used for the realization of numerical simulation have been designed. After this simulation, band formation analysis was performed using varios steps for each sample, and compared with the test specimen of the same formation with different geometrical notches. Finally, it was verified that both the shear band formation and the fracture characteristics of the studied material are directly related with the geometrical shape of the notch.

We study the nonlinear magnetic excitation in an anisotropic ferromagnet with a magnetic field. In the long wave approximation, the Landau-Lifschitz equation with easy axis anisotropy is transformed into the nonlinear Schrödinger type. By means of a straightforward Darboux transformation we obtain the one- and two-soliton solutions of uniaxial anisotropic ferromagnet. From a careful analysis for the asymptotic behavior of two-soliton solution we find that the collision between two magnetic solitons is elastic. This will be very helpful to understand the significant nature of the interactions between solitons in the future.

We investigate the equilibrium magnetic properties of a simple cubic small ferromagnetic particle under an external magnetic field. Although the particle is small, it can not be considered as a single-domain unit. The magnetic moments are represented by unitary spin vectors and we consider ferromagnetic interactions between nearest-neighbor spins. The coupling between spins is given in terms of the classical Heisenberg Hamiltonian and we also include a Zeeman contribution and a single-ion uniaxial anisotropy. The size of the particle changes from one to twelve lattice spacings. We employ in our study mean-filed calculations and Monte Carlo simulations. The magnetization and susceptibility curves as a function of temperature show that an uniaxial anisotropy can mimic a ferromagnetic or an antiferromagnetic coupling, depending on the angle between the external magnetic field and the easy axis.

We report the effect of temperature on the ferromagnetic resonance (FMR) spectra of Ni50Fe50 thin films sputtered on Si (001) wafers. The FMR field and linewidth were studied as a function of the ferromagnetic layer thickness, t, and the temperature, T. The data are interpreted in the framework of a phenomenological model that includes in- and out-of- the plane uniaxial anisotropy fields. The main effect of temperature on the magnetic properties of these films is to induce a surface anisotropy with an out-of- the plane uniaxial axis. The resonance field as a function of temperature, shows three different regimes, with two transition temperatures. Also, the temperature effects on the FMR spectra of these films are connected with the temperature variations of the surface anisotropy. A new magnetic transition is observed in thinner films at low temperatures.

Reportamos el efecto de la temperatura en el espectro de la resonancia ferromagnética (FMR) en películas de Ni50Fe50 depositadas sobre el substrato de Si(001). El campo de FMR y el ancho de línea fueron estudiados como una función del espesor de la película ferromagnética, t, y de la temperatura, T. Los datos son interpretados con un modelo fenomenológico que incluye campos de anisotropía uniaxial en el plano y fuera del plano. El principal efecto de la temperatura es inducir una anisotropía de superficie que produce un eje uniaxial fuera del plano. El campo de resonancia presenta tres regímenes de temperatura diferentes, con dos temperaturas de transición. El efecto de la temperatura sobre los espectros de FMR se explica en términos de las variaciones de la anisotropía de superficie con la temperatura. Una nueva transición de orden ferromagnético se observa a baja temperatura en la películas mas delgadas.

Nesse trabalho foi estudada a anisotropia no comportamento à fluência de cerâmicas de Si3N4 prensadas a quente. Quatro tipos de cerâmicas à base de Si3N4 foram desenvolvidas, utilizando-se Al2O3-CRE2O3 ou AlN e CRE2O3 como aditivos, em frações volumétricas de 5 e 20%. CRE2O3 é um óxido misto de ítrio e terras raras produzido na FAENQUIL. As misturas de pós foram submetidas à prensagem uniaxial a quente, a 1750 °C - 20 MPa. As amostras sinterizadas apresentaram fases cristalinas e microestruturas distintas, e foram submetidas a ensaios por compressão a 1300 °C, sob tensão de 300 MPa. Corpos de prova foram confeccionados nos planos paralelo e perpendicular ao eixo de prensagem a quente, e as taxas de fluência para ambos os planos foram obtidas e correlacionadas. Os resultados demonstraram que as amostras confeccionadas no plano perpendicular ao eixo de prensagem a quente, sofreram maiores deformações que as amostras do plano paralelo. Esse comportamento é devido à orientação dos grãos alinhados com o eixo de aplicação de carga compressiva durante os ensaios de fluência.

In this work the anisotropy of the creep behavior in hot pressed Si3N4 ceramics was evaluated. Four different Si3N4 ceramics were developed, using Al2O3-CRE2O3 or AlN e CRE2O3 as sintering aids. Specimens were hot pressed at 1750 °C - 20 MPa. The sintered specimens show different crystalline phases and microstructures, and were submitted to compressive creep tests at 1300 °C and stress of 300 MPa. Specimens in the parallel and perpendicular plane to the hot pressing axis were tested and the creep rates and strain were correlated as a function to the plane analyzed. The results show the influence of anisotropy on the creep behavior, related to the orientation of the grains, activating the rotation of the grains by viscous flow of the intergranular phase.