A new radial basis integration method applied to the boundary element analysis of 2D scalar wave equations

A new integration method named the Radial Basis Integration Method (RBIM) that include the Kriging Integration Method (KIM) Narváez and Useche (2020) as a particular case and performs boundary only offline precomputations for the creation of a meshless quadrature was developed for its application in boundary elements. Herein, as in DR-BEM, the inertial term is approximated using radial basis functions, however, its particular solution is not needed. The quadrature is now obtained in a simpler way than in KIM, because the evaluations of domain integrals necessary to compute the weights of quadrature points, is done transforming those to the boundary instead of using the Cartesian Transformation Method. Using RBIM, weakly singular domain integrals may be computed with good accuracy over complex domains. The results obtained in some scalar wave propagation problems using both Houbolt-a and Newmark-a time marching methods show that this procedure can be even more accurate than other used in BEM analysi

Estimación de esfuerzos inducidos durante el llenado y vaciado de silos metálicos para almacenamiento de cemento

The present article show the structural analysis realized to metallic silo for storage cement through of the parametric model development in the finite element software ASNYS APDL, the fill and discharge pressures applied on the silo wall is determined with the Eurocode normative EN 1991-4.The model is development with type shell elements allowing that the structure silo fits to the cylindrical and conical geometric of the silo. It explains each of the phases having the development of the model and is made a detailed analysis of the results delivered by the software; different models are evaluated changing the sheet thickness for select the most appropriate. Also the results are analyzed when be changing the tilting the hopper and is reviewed the behavior of the silo when is analyzed with its structure. © The author; licensee Universidad Nacional de Colombia

Modelado numérico de la propagación de fractura por fatiga utilizando el método de los elementos de contorno

The work presents a computer tool based on the boundary element method (BEM), that allows the study of the propagation of fracture phenomenon in structures which have sustained cyclical efforts. The code functions to develop computer models focused on the study of residual resistance of fractured bi-dimensional components based on linear elastic fracture mechanics (LEFM). The boundary element formulation of the problem is presented, as well as its computer implementation and its application to the specific problem analysis of fracture growth by fatigue. Fracture growth is modeled through the theory proposed by Paris, applied to the case of flat elasticity, and the criteria of maximum main efforts is used to define the direction of propagation (Portela, 1992). The BEM formulation was implemented in a computer code developed in Matlab 7.0 . The program has demonstrated effectiveness in predicting trajectories of propagation and residual resistance by fatigue, allowing its use as a tool of analysis in engineering.El trabajo presenta una herramienta computacional basada en el método de los elementos de contorno, (boundary element method –BEM–), que permite estudiar el fenómeno de propagación de fractura en estructuras sometidas a esfuerzos cíclicos. El código sirve para desarrollar modelos computacionales enfocados al estudio de resistencia residual de componentes bidimensionales fracturados, basados en la mecánica de la fractura lineal elástica, (linear elastic fracture mechanics –LEFM–). Se presenta la formulación por elementos de contorno del problema, su implementación computacional y su aplicación al análisis de problemas específicos de crecimiento de fractura por fatiga. El crecimiento de la fractura es modelado a través de la teoría propuesta por Paris, aplicada al caso de elasticidad plana, y es usado el criterio de esfuerzos principales máximos para definir la dirección de propagación (Portela, 1992). La formulación BEM fue implementada en un código computacional desarrollado en Matlab 7.0 . El programa ha demostrado efectividad para predecir trayectorias de propagación y resistencia residual por fatiga, permitiendo su uso como herramienta de análisis en ingeniería

Magnetic Materials by Melt Spinning Method, Structural Characterization, and Numerical Modeling

Chill block melt spinning is used in industrial processes for the production of metallic glasses. It is a rapid solidification process whereby a liquid metal is ejected at high pressure and temperature via a nozzle onto a rotating wheel solidifying in the form of a ribbon. In this work, starting from an alloy with the composition of Fe78Si9B13 (% at.) reproduces the melt spinning technique to get the amorphous magnetic material. A CFD3D model based on the finite volume method (FVM) is proposed. For this purpose, the OpenFoam® open source code is used. In the ribbon production stage, it has been observed that the turbulence involved in the first reported transient lasts a few milliseconds, enough time to study the process with high-speed cameras. We measure the ejection speed by using optical flow on the melt contour. This enables us to check defects in the ribbons, which are predicted with the computational model, such as the case of cracks caused by irregularities in the first formation of the solid layer. The temperature measurement method relies on the fact that the digital camera is sensitive to electromagnetic radiation between 400 and 1000 nm in wavelength and the fact that the image gray level, which is proportional to the temperature T, provided the background illumination level is negligible

Diseño del sistema de transporte de materia prima para la planta PVC de Tuvinil de Colombia S. A

La industria de los productos plásticos, cada día va en alza, hoy día nos tropezamos con bolsas, empaques, accesorios, tuberías, molduras, frascos, etc. La fabricación de esa variedad de elementos se debe a la realización de procesos de manufactura muy conocidos, tales como extrusión, inyección, soplado, en fin toda clase de procedimientos que transforman los diferentes compuestos plásticos como son los poliuretanos, polipropileno, policloruro de vinilo, ABS, polietilenos, etc. Dichos compuestos generados en industrias petroquímicas son procesados en empresas como TUVINIL de Colombia S.A. que se dedica fundamentalmente a la elaboración de tuberías y accesorios en PVC y Polietileno, se han encargado de satisfacer al gremio nacional de la construcción, y en los últimos años al internacional. Para mantenerse vigente y tecnológicamente al día en cuanto a la elaboración de estos elementos, se han planteado la tarea de modificar el manejo de su materia prima para la fabricación de tuberías y accesorios de PVC.Incluye bibliografí

Thermoplastic Starch (TPS)/Polylactic Acid (PLA) Blending Methodologies: A Review

Polylactic acid (PLA) and thermoplastic starch (TPS) are biodegradable polymers of biological origin, and the mixture of these polymers has been studied due to the desirable mechanical properties of PLA and the low processing cost of TPS. However, the TPS/PLA combination is thermodynamically immiscible due to the poor interfacial interaction between the hydrophilic starch granules and the hydrophobic PLA. To overcome these limitations, researchers studied the modification, processing, and properties of the mixtures as a strategy to increase the compatibility between phases. This review highlights recent developments, current results, and trends in the field of TPS/PLA-based compounds during the last two decades, with the main focus of improving the adhesion between the two components. The TPS/PLA blends were classified as plasticized, compatible, reinforced and with nanocomposites. This article presents, based on published research, TPS/PLA combinations, considering different methods with significant improvements in mechanical properties, with promising developments for applications in food packaging and biomedicineUniversidad Tecnológica de Bolíva

Characterization and Modeling of the viscoelastic behavior of hydrocolloid-based films using classical and fractional rheological models

Hydrocolloid-based films are a good alternative in the development of biodegradable films due to their properties, such as non-toxicity, functionality, and biodegradability, among others. In this work, films based on hydrocolloids (gellan gum, carrageenan, and guar gum) were formulated, evaluating their dynamic rheological behavior and creep and recovery. Maxwell’s classical and fractional rheological models were implemented to describe its viscoelastic behavior, using the Vortex Search Algorithm for the estimation of the parameters. The hydrocolloid-based films showed a viscoelastic behavior, where the behavior of the storage modulus (G ) and loss modulus (G00) indicated a greater elastic behavior (G 0 > G00 ). The Maxwell fractional model with two spring-pots showed an optimal fit of the experimental data of storage modulus (G0) and loss modulus (G00) and a creep compliance (J) (Fmin 0.98). This shows that fractional models are an excellent alternative for describing the dynamic rheological behavior and creep recovery of films. These results show the importance of estimating parameters that allow for the dynamic rheological and creep behaviors of hydrocolloid-based films for applications in the design of active films because they allow us to understand their behavior from a rheological point of view, which can contribute to the design and improvement of products such as food coatings, food packaging, or other applications containing biopolymers

Caracterización mecánica y microestructural de acero naval sometido a cargas dinámicas por explosión

The work presents the mechanical and micro-structural characterization of the grade A ASTM A 131 steel laminate that form naval panels (reinforced laminate with defined ratios aspect l/b), attained by means of destructive testing, to establish the mechanical response of naval structures submitted to those types of charges. Measurements of micro-hardness, grain size and tension tests of specimens of the material were carried out before and after the impact. The material hit was selected from structural panels submitted to controlled explosions generated nearby with 25g charges of pentolite, placed at predetermined distances. For the characterization, panels with the presence of fissures were rejected. Important variations in micro-hardness and mechanical characteristics appeared; nevertheless, significant micro-structural changes were not observed in grain size.El trabajo presenta la caracterización mecánica y microestructural de láminas de acero ASTM A 131 grado A que conforman paneles navales (láminas reforzadas con relaciones de aspecto l/b definidas), realizada mediante ensayos destructivos, para establecer la respuesta mecánica de estructuras navales sometidas a ese tipo de cargas. Se hicieron mediciones de microdureza, tamaño de grano y ensayos de tensión a especímenes del material antes y después del impacto. El material impactado fue seleccionado de paneles estructurales sometidos a explosiones controladas cercanas generadas con cargas de 250 g de pentolita, dispuestas a distancias predeterminadas. Para la caracterización se rechazaron paneles con la presencia de fisuras. Se presentaron variaciones importantes en microdureza y características mecánicas, sin embargo, no se observaron cambios microestructurales en tamaño de grano que fueran significativos

Modelado numérico de la propagación de fractura por fatiga utilizando el método de los elementos de contorno

The work presents a computer tool based on the boundary element method (BEM), that allows the study of the propagation of fracture phenomenon in structures which have sustained cyclical efforts. The code functions to develop computer models focused on the study of residual resistance of fractured bi-dimensional components based on linear elastic fracture mechanics (LEFM). The boundary element formulation of the problem is presented, as well as its computer implementation and its application to the specific problem analysis of fracture growth by fatigue. Fracture growth is modeled through the theory proposed by Paris, applied to the case of flat elasticity, and the criteria of maximum main efforts is used to define the direction of propagation (Portela, 1992). The BEM formulation was implemented in a computer code developed in Matlab 7.0 . The program has demonstrated effectiveness in predicting trajectories of propagation and residual resistance by fatigue, allowing its use as a tool of analysis in engineering.El trabajo presenta una herramienta computacional basada en el método de los elementos de contorno, (boundary element method –BEM–), que permite estudiar el fenómeno de propagación de fractura en estructuras sometidas a esfuerzos cíclicos. El código sirve para desarrollar modelos computacionales enfocados al estudio de resistencia residual de componentes bidimensionales fracturados, basados en la mecánica de la fractura lineal elástica, (linear elastic fracture mechanics –LEFM–). Se presenta la formulación por elementos de contorno del problema, su implementación computacional y su aplicación al análisis de problemas específicos de crecimiento de fractura por fatiga. El crecimiento de la fractura es modelado a través de la teoría propuesta por Paris, aplicada al caso de elasticidad plana, y es usado el criterio de esfuerzos principales máximos para definir la dirección de propagación (Portela, 1992). La formulación BEM fue implementada en un código computacional desarrollado en Matlab 7.0 . El programa ha demostrado efectividad para predecir trayectorias de propagación y resistencia residual por fatiga, permitiendo su uso como herramienta de análisis en ingeniería

Modelado numérico de la propagación de fractura por fatiga utilizando el método de los elementos de contorno

The work presents a computer tool based on the boundary element method (BEM), that allows the study of the propagation of fracture phenomenon in structures which have sustained cyclical efforts. The code functions to develop computer models focused on the study of residual resistance of fractured bi-dimensional components based on linear elastic fracture mechanics (LEFM). The boundary element formulation of the problem is presented, as well as its computer implementation and its application to the specific problem analysis of fracture growth by fatigue. Fracture growth is modeled through the theory proposed by Paris, applied to the case of flat elasticity, and the criteria of maximum main efforts is used to define the direction of propagation (Portela, 1992). The BEM formulation was implemented in a computer code developed in Matlab 7.0 . The program has demonstrated effectiveness in predicting trajectories of propagation and residual resistance by fatigue, allowing its use as a tool of analysis in engineering.El trabajo presenta una herramienta computacional basada en el método de los elementos de contorno, (boundary element method –BEM–), que permite estudiar el fenómeno de propagación de fractura en estructuras sometidas a esfuerzos cíclicos. El código sirve para desarrollar modelos computacionales enfocados al estudio de resistencia residual de componentes bidimensionales fracturados, basados en la mecánica de la fractura lineal elástica, (linear elastic fracture mechanics –LEFM–). Se presenta la formulación por elementos de contorno del problema, su implementación computacional y su aplicación al análisis de problemas específicos de crecimiento de fractura por fatiga. El crecimiento de la fractura es modelado a través de la teoría propuesta por Paris, aplicada al caso de elasticidad plana, y es usado el criterio de esfuerzos principales máximos para definir la dirección de propagación (Portela, 1992). La formulación BEM fue implementada en un código computacional desarrollado en Matlab 7.0 . El programa ha demostrado efectividad para predecir trayectorias de propagación y resistencia residual por fatiga, permitiendo su uso como herramienta de análisis en ingeniería