Ls-Dyna

The paper focuses on simulation & analysis of a Rear Under Run Protection (RUPD) system under crash scenario. The basic objective is to improve the safety of the car and the occupants by designing the RUPD and car bumper. The choice of material and the structural design are the two major factors for impact energy absorption during a crash. It is important to know the material & mechanical properties and failure mechanism during the impact. This study concentrates on component functions, geometry, behavior of material and other parameters that influence the compatibility of the car bumper and rear under run protection device. The analysis was carrying out using Finite Elements software (LS-Dyna), Meshing tools by Altair Hyper mesh and Modeling on Pro-E. This analysis is a partial work of a major project wherein the RUPD will be subjected to static testing with variable load distributions at different locations on RUPD. The analysis establishes the method and parameters of the simulation on modeling and analysis software used by demonstrating the energy absorption pattern in bumper and RUPD during frontal crash of a car with different design parameters of RUPD.

RESUMEN: Los muros no estructurales pueden ser desplazados de un lugar a otro por variaciones en el uso de los espacios, originando aún durante sismos moderados, una interacción pórtico-relleno que puede alterar significativamente la concepción de los diseños convencionales. Por lo tanto, es necesario evaluar la influencia que tienen estos rellenos en el comportamiento inelástico local y global de los edificios, especialmente cuando esta interacción causa efectos negativos a los elementos que conforman el sistema. Teniendo en cuenta lo anterior, se presentan en este trabajo los resultados de una investigación analítica y computacional, donde se realiza la modelación inelástica de tres edificios típicos (de 3, 7 y 13 pisos) utilizando el método del puntal diagonal equivalente, con el propósito de cuantificar la influencia (positiva ó negativa) de los rellenos de mampostería en el comportamiento local y global de las edificaciones. Adicionalmente se presenta una herramienta que permite tener en cuenta estos elementos durante el proceso de análisis y diseño estructural.

Considering the actual consumer habits for precooked food, in the present work the combined drying (microwave and hot air convection) was carried out with pretreated osmotic dehydrated potatoes. The use of osmotic dehydration as a pretreatment in the food industry improves the product quality in terms of colour, flavour and texture. The advantage of the combined drying, microwave and convection with hot air aims at a better drying rate preserving the organoleptic properties of the product when is compared with the convective drying with hot air or microwave only. The osmotic dehydration during 1 or 2 hours and the salt concentration (5 or 10 % w/w) were analyzed, before the combined drying. Also, the results of the combined drying at different powers of 40, 50 and 60 %, after a pretreatment with osmotic dehydration during 1 hour was studied.

Effect of addition of Yttria partially stabilized Zirconia powder to dental porcelain was studied. The zirconium powder was incorporated in 3, 5 and 7-percent by weight to dental porcelain powder. The measured properties were flexural strength, modulus of elasticity, fracture toughness and hardness. Samples were prepared according to the manufacturers instructions. Zirconia powder was thoroughly mixed with the porcelain powder in the correct weight percent before use. Flexural strength, modulus of elasticity, and fracture toughness were measured using three-point bending test. The hardness was measured using a conventional microhardness tester. All data were collected and analyzed with one-way analysis of variance (ANOVA) and LSD test (p=0.05). The results indicated that the addition of 3 % and 5 % Yttria partially stabilized Zirconia to the conventional dental porcelain powder resulted in increased flexural strength and fracture toughness of the porcelain. On the contrary, 3 % and 5 % zirconia decreased both the modulus of elasticity and hardness. In addition, 7 % zirconium powder decreased the studied properties. X-ray examination showed that zirconia addition increased the radiopacity of the material. It was concluded that zirconia-modified dental porcelain was stronger and tougher than the conventional unmodified ceramic.

Composite materials are being widely used in automobile industry in order to meet the ever increasing demand to achieve significant weight reduction by maintaining the performance levels. Additionally, there are a number of challenging crashworthiness criteria set by the regulating authorities in various countries for vehicle safety, which the vehicle has to qualify. In these cases composites can be very useful as they exhibit high strength to weight ratios. But, deformation modes of composites are more complex when compared to metals, due to which it is more important to analyse the behaviour of composites under impact. In this study four types of cross sections (square, cylindrical, hexagonal and decagonal) were considered for the geometric shapes of GFRP (glass fiber reinforced plastic) crash boxes. Drop weight impact testing is widely used for studying the behaviour of parts subjected to impact loadings. The drop weight impact testing is highly dynamic in nature and in addition various factors like data acquisition signal noise (disturbance) requires the user to test 3-4 samples for each test specimen, for repeatability and minimisation of errors, which thereby increases the total number of testing samples. Therefore, in practise only a limited number of specimens can be actually tested using drop weight impact test considering the number of specimen samples to be manufactured and the cost involved in it. In this paper the development of numerical simulation model for drop weight impact test and its correlation with the real time drop weight impact testing was discussed in detail. à PART_COMPOSITE model along with à MAT58 material card was used for laminated GFRP composite specimen in Ls-Dyna along with calibration of parameters like longitudinal compression stress limiting factor (SLIMC1) and softness factor (SOFT) for simulation. The numerical simulation was correlated with the experimental data using correlation factors. The deformation modes as well as the F-D (force versus displacement) curves and SEA (specific energy absorption) values were found to have a close match between experiments and finite element simulations.

There is an ever-increasing demand in the automotive sector to continuously improve the performance and reduce cost through weight reduction in the structure of the vehicle. In the present scenario, it is also necessary to meet the standards set by crash safety regulating authorities in various parts of the world. In automobiles, the crash box is placed in the anterior region to absorb the impact energy in the event of an accident. Glass fiber reinforced plastic crash boxes have a high strength-to-weight ratio and also are good in energy absorption, particularly useful in this scenario. In this paper, the effectiveness of different triggers in combination with various geometries is investigated for Glass fiber reinforced plastic crash boxes using drop-weight impact testing. A trigger is a geometric irregularity introduced in the crash box design to alter the energy as well as force levels by modifying the deformation mode under loading. Comparison of change in force level, absorption of impact energy, specific energy absorption values was performed for composite crash boxes made of various types of cross-sectional geometries along with multiple patterns of triggers. Force versus displacement (F-D) curves are drawn for all the cases of the glass fiber reinforced plastic crash boxes to understand the behavior of each combination formed with various types of geometries and triggers, under impact loading. Strength-to-weight ratio was considered as the deciding factor for the comparisons to know the best and worst cases of the crash boxes made of different cross-sections along with various trigger types. This study provides detailed insights into the drop-weight impact testing procedure including the preparation of specimens, setting up the drop-weight impact test, preparation of specimen clamps, safety precautions involved, data acquisition from the test and its processing. Composite, crash box, crashworthiness, drop-weight impact test, glass fiber reinforced plastic, trigger Date

An automobile crash box is a thin walled structure made of metal or composite material which is mounted on the front region of the vehicle. Its main purpose is to absorb the energy due to collision in the event of a crash. Crash boxes made of metals like steel and aluminum are widely used whereas use of composite crash boxes is in development phase in automobile industry. In automobile industry there is always a quest to reduce the mass of the vehicle for reduction of raw material usage and also to increase fuel efficiency. Composite crash boxes provide very good weight to stiffness ratio which makes them good contenders. But the behaviour of parts made of composite material in impact or collisions has to be understood for its usage in automobile structure. Crash box plays an important role in the event of a frontal collision of the vehicle. A crash box should absorb maximum possible energy and should deform sequentially so that the deformation pattern is not random. In this paper the effect of various types of triggers is investigated for GFRP composite crash boxes. Trigger is a geometrical feature applied to the crash box with the objective of achieving the desired energy absorption, deformation pattern and peak force. A comparative study of variation of peak forces, energy absorbed, S.E.A (specific energy absorbed) was done with the variation of triggers for crash box. Force vs. displacement curves were plotted for each case providing detailed insights into the force variation during deformation.

Se realiza un estudio del tratamiento de señales con el algoritmo de filtrado de Fourier y de localización de fallas por tres algoritmos diferentes y se presenta un software sobre MATLAB para la determinación (con información de un extremo) de la distancia a la falla en Líneas de Transmisión Eléctricas (LTE) a partir de registros oscilográficos obtenidos de relevadores digitales en eventos que por sus características e importancia lo requieran. Un procedimiento con el que fueron tratados 15 registros de eventos reales valida la mejora del proceso de localización con la aplicación de dicho software. Se presenta un resumen en forma de tabla del tratamiento de estos registros. Se recomienda su uso por personal calificado que pueda determinar de forma visual los mejores intervalos de aplicación, también se recomienda en el estudio de fallos repetitivos o al corroborar localizaciones previas realizadas por equipamientos digitales.

This paper presents the vibration analysis of sandwich panels and a comparison of natural frequencies using various theories. A simple software has been developed for calculating the natural frequency of panels. The software was validated by comparing the natural frequency using the software package NISA and ANSYS

Muchas regiones en Colombia presentan un déficit en registros de variables hidroclimatológicas, es por eso que, para poder entender el comportamiento espacial y temporal de estas variables en una cuenca hidrográfica, se requiere del uso de diferentes técnicas y modelos que permitan representar con suficiente precisión este comportamiento a partir de la escasa información existente. En este documento, se presenta una aproximación al modelamiento del comportamiento hidrológico de las cuencas de los ríos Turbo, Guadualito y Currulao localizadas en la región de Urabá (Colombia), utilizando información hidroclimatológica escasa (precipitación y caudal), para lo cual se calibra un modelo lluvia-escorrentía agregado ("Modelo de Tanques") a escala diaria en cada una de las tres cuencas, el cual puede ser utilizado para la simulación de escorrentía en cuencas no instrumentadas con estaciones de caudal en dicha región, además, se estiman los campos promedios anuales de precipitación y evapotranspiración en la región, los cuales son utilizados para el cálculo de los caudales medios multianuales empleando el método del balance hidrológico de largo plazo, al cual se le calcula la incertidumbre

This article focuses on one of the steps proposed by the authors as a framework for improving the management of post-sale service. Specifically, the referred step tries to apply root cause analysis of failures to improve the organization of warranty support. This analysis can help make better decisions within the scope of after-sales service, for example, whether a particular incident should be treated under warranty or not. This article begins with an introduction to the current concept of warranty, briefly describing the proposed framework and the relevant literature related to such customer service. Thus, the reader can place the step to be developed in a context of useful tools and methodologies for the management of postsale service. Therefore, the main aspects of Root Cause Analysis are defined with the intention to apply these concepts in the management of those incidents reported by the user. With this objective, this article aims to adapt a developed and applied tool of the maintenance management (Root Cause Analysis) to a new field, in this case, the customer service. At the end of this article the main contributions for this work are summarized.

This article focuses on one of the steps proposed by the authors as a framework for improving the management of post-sale service. Specifically, the referred step tries to apply root cause analysis of failures to improve the organization of warranty support. This analysis can help make better decisions within the scope of after-sales service, for example, whether a particular incident should be treated under warranty or not. This article begins with an introduction to the current concept of warranty, briefly describing the proposed framework and the relevant literature related to such customer service. Thus, the reader can place the step to be developed in a context of useful tools and methodologies for the management of postsale service. Therefore, the main aspects of Root Cause Analysis are defined with the intention to apply these concepts in the management of those incidents reported by the user. With this objective, this article aims to adapt a developed and applied tool of the maintenance management (Root Cause Analysis) to a new field, in this case, the customer service. At the end of this article the main contributions for this work are summarized.

Medellín. Con base en esta metodología se concluyó que Medellín presenta un nivel de ruido diurno global de 73dB(A), indicando que su zona urbana tiene niveles de ruido apropiados solo para sectores industriales. De igual manera en la noche, se presenta un nivel de ruido global de 68 dB(A), apropiado solo para el mismo tipo de sector.

El objetivo del presente trabajo es analizar espacialmente el parámetro salinidad en la planicie aluvial del río Motatán, en el estado Trujillo. El área tiene una extensión aproximada de 705.360 Km2 emplazadas en una región potencialmente agrícola. El estudio proporciona una estimación de la variación espacial de salinidad en el acuífero durante el período 1994-1999. Para la obtención de los datos básicos se recopiló, procesó y analizó toda la información de campo levantada en la red de muestreo existente, por el Sistema Hidráulico Trujillano, para ello se contó con los datos de conductividad eléctrica, niveles piezométricos, cotas de pozos, coordenadas UTMX y UTMY de cada uno de los pozos, información de cultivos entre otros y se aplicaron conceptos, técnicas y métodos geoestadísticos. A partir del muestreo de 101 pozos ubicados en el área de estudio, se aplicó el krigeado para la conductividad eléctrica, y en el análisis se observó que esta presenta un ligero incremento hacia el oeste de la planicie. Finalmente, se recomienda densificar la red de muestreo para así obtener información del comportamiento de la variable en estudio en toda la superficie de la planicie aluvial.

RESUMEN: En la actualidad, el incremento de la resistencia en nuevos materiales y las mayores luces entre apoyos hacen que los puentes peatonales sean más susceptibles a problemas de vibraciones excesivas. Infortunadamente las provisiones de las normas colombianas son limitadas para el diseño o rehabilitación de estas estructuras. En este artículo se presenta una clasificación de los puentes peatonales en Santiago de Cali que permite comparar efectos de la Interacción Humano-Estructura, aceleraciones máximas y frecuencias naturales, con los criterios de vibraciones para diseño especificados en las principales normas. Aunque en los 19 puentes estudiados no se superaron los límites de aceleraciones establecidas por las normas por una persona al caminar, 16 de los puentes presentaron vibraciones que generaron incomodidad en los peatones. En consecuencia, se recomienda que futuras normas colombianas establezcan valores límites de aceleraciones y frecuencias naturales en función del desempeño según niveles de comodidad y seguridad percibida por los peatones. PALABRAS CLAVE: Interacción humano-estructura, vibración en puentes peatonales, cargas de servicio en puentes, respuesta dinámica, cargas antrópicas.

A principal cause of traumatic brain injury is rotational head acceleration, which can induce brain injury even in absence of a direct impact to the head. A bicycle fall typically leads to an oblique impact of the head that induces rotational head acceleration. To mitigate this rotational head acceleration, a novel bicycle helmet concept has been developed that employs a collapsible cellular structure. This study quantified the efficacy of this technology in comparison to traditional bicycle helmets made of rigid Expanded Polystyrene (EPS). Prototype helmets with the Cellular structure (CELL) and standard EPS helmets (CONTROL) were subjected to oblique impacts in vertical drop tests onto angled anvils. Helmets were tested at impact speeds of 4.8 m/s and 6.2 m/s and at impact angles of 30°, 45°, and 60°. Linear and rotational headform acceleration and neck loads of an anthropometric head-neck surrogate were recorded and peak axonal strain was estimated from headform kinematics. CELL helmets significantly reduced rotational acceleration and associated axonal strain in all tests compared to CONTROL helmets, with reductions ranging from 34%-73% for rotational acceleration and 63%-85% for axonal strain. Results demonstrate the potential of the novel bicycle helmet strategy to reduce rotational head acceleration and axonal strain associated with brain injury risk.

Naturally ventilated barns have the advantage of providing an energy-efficient and low-noise micro-environment for animals. Such barns are very common, especially for cattle, which are a major source of ammonia and methane emissions as well as other airborne pollutants. Emission fluxes are calculated as the product of the ventilation rate (VR) and the gas concentration. The VR of naturally ventilated barns are directly influenced by atmospheric conditions. Therefore, the estimation of VR involves high uncertainties; furthermore, there is no reference method for VR estimation. For these reasons, three different methods were investigated to estimate VR through naturally ventilated dairy barns: (1) the tracer gas technique, using radioactive isotope Krypton-85 ( 85 Kr), (2) the measurement of the air velocity through the barn openings, and (3) the natural ventilation method. The investigations were performed in two naturally ventilated dairy barns (each with a volume of 5,670 m 3 ) during mild (T≥17℃) and cold weather (T<17℃) conditions. The VR ranged between 48,000 and 475,000 m 3 /h. There was a significant (p<0.01) correlation between all three methods for barn A (Pearson's correlation coefficient 0.59-0.86). For barn B only, the tracer gas and the natural ventilation method showed a significant (p=0.03) correlation (Pearson's correlation coefficient 0.62). The season (mild or cold) and the VR estimation method both had a significant (p<0.03) effect on the estimated VR for both barns. The outside wind speed had a significant (p<0.005) effect on the estimated VR for barn A. For barn B, this effect was not significant (p=0.052). The tracer gas technique used has the advantage of measuring the tracer with high resolution in time (1 Hz) and space (18 or more measured points).

químicamente presentan mayores contenidos de grupos ácidos, para las condiciones experimentales de trabajo, que las muestras obtenidas por activación térmica. Para los carbones activados térmicamente los valores de gmpos ácidos y básicos son bajos; entre 0,20 y 0,72 meq g'. Se obtienen carbones activados a partir de cuesco de palma africana, mediante activación química con K2CO3 y activación térmica con CO2. El material inicial se somete a diferentes condiciones de temperamra de carbonización (600,750 y 900 °C) y diferentes tiempos de carbonización (1,0; 1,5; 2,0; y 2,5 horas) con el objetivo de observar cómo afectan estas condiciones la porosidad del material. Se observa bajo desarrollo de la porosidad en los carbones carbonizados a 900 °C y activados químicamente. La acidez y basicidad a cada uno de los carbones activados obtenidos se determinan por timlación con soluciones 0.05 M de hidróxido de sodio y de ácido clorhídrico, respectivamente. Las muestras activadas ABSTRACT Activated carbons are obtained starting from stone of African Palm, by means of chemical activation with K2CO3 and thermal activation with CO2. The initial material undergoes different conditions of carbonization temperamre 600,750 and 900 °C -and different times of carbonisation-1.0; 1.5; 2.0; and 2.5 hours-with the objective of observing how these conditions affect the porosity of the material. It is observed a low development ofthe porosity in the carbons carbonized to 900 °C and activated chemically. The acidity and basicity are determined, for each one ofthe activated carbons obtained, for titration with solutions 0.05 M of sodium hidroxide and of hydrochloric acid

Esta investigación se fundamentó en el análisis y caracterización de los electrodos INDURA utilizados para recubrimiento y recuperación de piezas, depositados como recargue duro (Hardfacing), sobre un sustrato de acero AISI/SAE 1020 mediante el proceso SMAW (Shielded Metal Arc Welding), con el objetivo de determinar la influencia del tipo de electrodo y el número de pases de soldadura sobre la resistencia al desgaste abrasivo. Las variables consideradas en el presente estudio fueron: tipo de electrodo (Overlay 60®, Overlay 62® y Oversugar®) y número de pases de soldadura (1 y 2). Se utilizó el ensayo de abrasión de acuerdo al procedimiento B de la norma ASTM G-65, ensayos de microdureza y microscopía convencional. Se determinó la pérdida de masa de las probetas recubiertas, con esto se halló el coeficiente de desgaste, el cual fue relacionado con la composición química de cada uno de los electrodos y el número de pases de soldadura. Se determinó que el recubrimiento Overlay 62® aplicado mediante dos pases generó el mayor rendimiento contra el desgaste abrasivo debido a que presentó la menor pérdida de masa y el menor coeficiente de desgaste.

The objective of this research study was to design and evaluate the MGS long-span design for use with unsupported spans greater than 25 ft (7.6 m). Two full-scale crash tests were conducted to evaluate the MGS long-span system with increased span lengths and the use of UBSP posts adjacent to the long span. Both tests were conducted according to the TL-3 criteria outlined in MASH. Both test nos. MGSLS-1 and MGSLS-2 were conducted with the 2270P vehicle impacting their respective critical impact points at a speed of 62 mph (100 km/h) and an angle of 25 degrees. Test no. MGSLS-1 was conducted to evaluate the potential for vehicle instability by selecting a critical impact point that maximized the interaction of the front wheel of the pickup truck with the wing wall of the culvert. Test no. MGSLS-2 was designed to evaluate the structural capacity of the system by selecting a critical impact point that maximized the potential for pocketing, wheel snag, and rail rupture. Test no. MGSLS-1 resulted in the vehicle being captured and redirected smoothly by the barrier system with all vehicle decelerations being within the recommended occupant risk limits. Therefore, test no. MGSLS-1 was deemed successful according to the TL-3 safety performance criteria found in MASH. Test no. MGSLS-2 resulted in the vehicle penetrating the barrier and creating multiple detached fragments that could present a safety hazard to oncoming traffic or the occupants of the vehicle. Therefore, test no. MGSLS-2 was deemed unsuccessful according to the TL-3 safety performance criteria. found in MASH.

Three full-scale vehicle crash tests were conducted according to the Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) safety performance criteria on a transition between the Midwest Guardrail System (MGS) and a portable concrete barrier (PCB) system. The transition system utilized for test nos. MGSPCB-1 through MGSPCB-3 consisted of a standard MGS that overlapped a series of Fshape PCB segments that approached the MGS at a 15H:1V flare. In the overlapped portion of the barrier systems, uniquely-designed blockout holders and a specialized W-beam end shoe mounting bracket were used to connect the systems. In test no. MGSPCB-1, a 5,079-lb (2,304-kg) pickup truck impacted the barrier at 63.2 mph (101.8 km/h) and 25.3 degrees. The barrier captured and redirected the 2270P vehicle, and the vehicle decelerations were within the recommended occupant risk limits. In test no. MGSPCB-2, a 2,601-lb (1,180-kg) car impacted the barrier at 65.1 mph (104.8 km/h) and 24.0 degrees. The barrier captured and redirected the 1100C vehicle, and the vehicle decelerations were within the recommended occupant risk limits. In test no. MGSPCB-3, a 5,177-lb (2,348-kg) pickup truck impacted the barrier at 63.1 mph (101.5 km/h) and 24.6 degrees. For this test, the system was impacted in the reverse direction. The barrier captured and redirected the 2270P vehicle, and the vehicle decelerations were within the recommended occupant risk limits. Based on the results of these successful crash tests, it is believed that the transition design detailed herein represents the first MASH TL-3 crashworthy transition between the MGS and PCBs.

Often, road construction causes the need to create a work zone. In these scenarios, portable concrete barriers (PCBs) are typically installed to shield workers and equipment from errant vehicles as well as prevent motorists from striking other roadside hazards. For an existing W-beam guardrail system installed adjacent to the roadway and near the work zone, guardrail sections are removed in order to place the portable concrete barrier system. The focus of this research study was to develop a proper stiffness transition between W-beam guardrail and portable concrete barrier systems. This research effort was accomplished through development and refinement of design concepts using computer simulation with LS-DYNA. Several design concepts were simulated, and design metrics were used to evaluate and refine each concept. These concepts were then analyzed and ranked based on feasibility, likelihood of success, and ease of installation. The rankings were presented to the Technical Advisory Committee (TAC) for selection of a preferred design alternative. Next, a Critical Impact Point (CIP) study was conducted, while additional analyses were performed to determine the critical attachment location and a reduced installation length for the portable concrete barriers. Finally, an additional simulation effort was conducted in order to evaluate the safety performance of the transition system under reverse-direction impact scenarios as well as to select the CIP. Recommendations were also provided for conducting a Phase II study and evaluating the nested MGS configuration using three Test Level 3 (TL-3) full-scale crash tests according to the criteria provided in the Manual for Assessing Safety Hardware, as published by the American Association of Safety Highway and Transportation Officials (AASHTO).

During a collision between an automobile and a road safety barrier, the vehicle will go through many behavior transition phases. This research will focus on determining the behavior of two car models including a sedan car and a pickup truck in collision with two safety road barriers using numerical simulation. This paper will also present images, total force graphs, and velocity graphs throughout the process to evaluate the vehicle's behavior at different impact speeds and angles. It is recognized that at similar impact speeds, collision angles, and barrier types, the pickup truck suffers more damage than the sedan. In addition, the pickup truck colliding with a concrete barrier exhibits the highest force, while the sedan colliding with a W-Beam barrier records the lowest force among the four collision types. Regarding the road safety barrier, the concrete barrier has a shorter force increase/decrease duration than the W-Beam barrier.

During a collision between an automobile and a road safety barrier, the vehicle will go through many behavior transition phases. This research will focus on determining the behavior of two car models including a sedan car and a pickup truck in collision with two safety road barriers using numerical simulation. This paper will also present images, total force graphs, and velocity graphs throughout the process to evaluate the vehicle's behavior at different impact speeds and angles. It is recognized that at similar impact speeds, collision angles, and barrier types, the pickup truck suffers more damage than the sedan. In addition, the pickup truck colliding with a concrete barrier exhibits the highest force, while the sedan colliding with a W-Beam barrier records the lowest force among the four collision types. Regarding the road safety barrier, the concrete barrier has a shorter force increase/decrease duration than the W-Beam barrier.

Se realiza un estudio del tratamiento de señales con el algoritmo de filtrado de Fourier y de localización de fallas por tres algoritmos diferentes y se presenta un software sobre MATLAB para la determinación (con información de un extremo) de la distancia a la falla en Líneas de Transmisión Eléctricas (LTE) a partir de registros oscilográficos obtenidos de relevadores digitales en eventos que por sus características e importancia lo requieran. Un procedimiento con el que fueron tratados 15 registros de eventos reales valida la mejora del proceso de localización con la aplicación de dicho software. Se presenta un resumen en forma de tabla del tratamiento de estos registros. Se recomienda su uso por personal calificado que pueda determinar de forma visual los mejores intervalos de aplicación, también se recomienda en el estudio de fallos repetitivos o al corroborar localizaciones previas realizadas por equipamientos digitales.

Assessing the behavior of composite structures which are subjected to impact loads is one of the important subjects in the field of mechanical sciences. Using thin-walled tubes which collapsed and absorbed the impact energy is a well-known method to prevent damages to the other parts of the structures. In this paper, deformations, crushing length, peak load, mean force and energy absorption capacity of thin-walled circular composite tubes are investigated both experimentally and numerically. In order to experimental study, three circular composite tubes were fabricated and subjected to quasi-static axial load. Also, a finite element model was constructed and analyzed under same conditions using FEM27 and LS-DYNA software packages. The results of simulations are in good agreement with the experimental data and show that the section geometry has considerable effect on the energy absorption. The circular composite tube has the most energy absorption capacity and the most average force ...

Teniendo en cuenta los problemas ambientales asociados con la producción del Cemento Portland (CP), en los últimos años se ha promovido el uso de la Ceniza Volante (CV) en la producción de concretos. La utilización de la CV se ha dado principalmente mediante su activación con el CP y como material cementante geopolimérico. En este artículo una tercera técnica de activación de la CV conocida como electrometagénesis es investigada. Esta consiste en la activación de la CV, a partir del ingreso de iones de una solución alcalina mediante la aplicación de un campo eléctrico a través del concreto endurecido. Como fuente de iones alcalinos se usaron soluciones de hidróxido de sodio/silicato de sodio con varias relaciones molares. Una vez terminado el tratamiento se evaluó la variación en la resistencia a la compresión, la velocidad de pulso ultrasónico y la microestructura de la matriz del concreto. Los resultados mostraron que los iones alcalinos migrados dentro del concreto reaccionaron con las partículas de CV mutando estas a nuevas fases, produciendo un aumento en sus propiedades.

This paper focuses on the design of steel plated girders under combinations of transverse loading, bending moment and shear force. In the member states of the European Union the design of slender steel plates is covered by EN 1993EN -1-5:2006. Although conclusions from literature show a rather significant interaction between transverse loading and shear force (F-V), no consideration of this type of interaction is made in Section 7.2 of EN 1993EN -1-5:2006. In order to close that gap experimental and numerical studies were undertaken to analyse the stability behaviour and to identify the influence of key parameters. Based on that an F-V proposal is developed which is completed by the consideration of a bending moment so that finally a fully usable F-M-V interaction equation is proposed.

Rolling dynamic compaction (RDC) is a ground improvement technique, which involves towing a non-circular module behind a tractor to achieve soil compaction. When compared against conventional static and vibratory compaction techniques, RDC is capable of compacting thicker layers of soil and at a faster operating speed. This study validates the developed numerical scale model against a field study using the full-size RDC module. Numerical results were compared with the field data in four aspects namely, displacements at the ground surface, and at depths of 0.7 and 1.1 m, pressures at 0.7 and 1.1 m depths, energy delivered by the RDC module into the underlying soil, and the depth of improvement. It is concluded that, numerical results are in good agreement with the field data. This paper also proposes that pressure results are an imperfect indicator to assess the optimum number of RDC passes, whereas, ground settlement is recommended since it better reflects ground improvement due to RDC and it has a clear relationship with the number of passes.

Rolling Dynamic Compaction (RDC) imparts energy to the ground via the use of a heavy non-circular module that rotates as it is towed, causing it to fall to the ground and compact it dynamically. This paper summarises the predictions of energy imparted to the ground from a single impact for both the standard (8-tonne), and heavy duty (12-tonne) 4-sided impact rollers. Several published case studies are summarised for the applications of: (1) improving ground in situ; and (2) compacting soil in thick layers. This paper addresses the need for these two distinctly different applications of RDC to be treated separately. Finally, this paper augments deep dynamic compaction theory and provides relationships for estimating the depths of soil that can be improved in situ, and layer thicknesses capable of being compacted by RDC.

RESUMEN: Estudios teóricos de la termólisis de -hidroxicetonas--aril sustituidas (m,p) para producir mezclas de aldehídos aromáticos y acetona a 429,15K se llevaron a cabo utilizando métodos ab-initio a niveles MP2/6-31G(d)//HF/6-31G(d). Los perfiles de reacción para los sustituyentes m y p estudiados muestran en todos los casos que la segunda etapa de la reacción tautomerización de acetona ( G ≠ =217.6 kJmol -1 ) es la etapa mas lenta. La primera etapa incluye un estado de transición cíclico de seis miembros y sobre ésta se centraron los estudios de una posible relación lineal de energía libre. Los resultados muestran que no hay una buena correlación Hammett indicativo de efecto perpendicular a la coordenada de reacción.

Moisture adsorption isotherms of amorphous cassava starch were determined at temperatures of 5, 30 and 45°C using a dynamic vapour sorption technique (DVS). Thirteen relative humidity values were set in a range from 0 to 94.5% for each temperature. Type-II isotherms were obtained in all cases. The effect of increasing temperature on the whole water activity range of the adsorption isotherms showed a decrease in the equilibrium moisture content. The data did not display any isotherm cross-over with temperature at elevated water activities as previously reported for this product using thymol as an antimicrobial agent. Different isotherm models were used to describe the sorption behaviour of amorphous cassava starch. The modified GAB model exhibited the best statistical results. For the temperature range studied, the A, B, C and D parameters in this model ranged from 0.127-0.255, 6.93-53.0, 0.493-0.0181 and 0.137-0.503, respectively. Monolayer water content ranged from 0.0547 to 0.0727 g.g -1 of dry solids using the BET equation and 0.0433 to 0.0637 g.g -1 of dry solids, when the GAB model was used. The net isosteric heat of sorption obtained ranged from 0.8 to 6.9 kJ.mol -1 in a moisture content range of 10-27 g.100 g -1 of dry solids. Contrary to previous research works no antimicrobial agents that could alter isotherms were used in isotherm determinations. Therefore, moisture adsorption data

Resumen. Se estudian los ciclos diurno y anual de la humedad relativa en 17 aeropuertos de Colombia, durante el período 1973de Colombia, durante el período -1993. Se analiza el ciclo diurno promedio de largo plazo, su variabilidad de acuerdo con la ubicación y la influencia que tienen sobre éste los ciclos anuales de la precipitación y de la temperatura. Para la humedad relativa (HR) se evidencian ciclos anuales bimodales con máximos en Abril-Mayo-Junio y Septiembre-Octubre-Noviembre (un poco mayores), y valores mínimos durante Julio-Agosto. En las regiones costeras, la humedad relativa evidencia valores altos, mayores del 70% en las horas de la mañana y tarde comparado con los bajos valores que se presentan a las mismas horas en las zonas del interior del país, lo cual aparece más marcado en las estaciones del litoral Pacífico donde los valores están por encima del 80%, a lo largo de todo el día. Se observan ciclos diurnos unimodales con mayores humedades temprano en la mañana entre las 4 y 7 LST, y los menores valores hacia las 13 y 16 LST. La fase del ciclo diurno no cambia durante el año, pero sí su amplitud, lo cual es consecuente con la fase del ciclo anual. Meses más húmedos implican humedades relativas diurnas mayores. Con respecto a la temperatura media anual se observan relaciones inversas con los valores de humedad relativa, tanto a nivel diurno como anual. Los mecanismos físicos que explican la dinámica diurna se asocian al ciclo diario del calentamiento radiativo, así como a la posición geográfica relativa a las fuentes de humedad, al paso de la zona de convergencia intertropical (ZCIT), a la dinámica del Chorro del Chocó, a los complejos convectivos de mesoescala, y a dinámicas locales y regionales de la circulación atmosférica.

A rig was developed to permit impacts on a Hybrid III 50 th-percentile male anthropomorphic test device (ATD) at selected velocities and head impact orientations in guided free-fall. This is to investigate the ability of a bicycle helmet to reduce angular head acceleration and subsequent brain injury in crashes, as well as the effects of helmets on neck injury. Helmets were able to reduce head linear acceleration significantly and angular accelerations in lateral impacts. There were no significant reductions in biomechanical predictors of neck injury risk in helmeted impacts as compared to unhelmeted impacts. At worst bicycle helmets do not appear to exacerbate head injury risks arising from angular acceleration or neck injury risks.

RESUMEN Considerando las implicancias ambientales en la fabricación de mezclas asfálticas en caliente se han desarrollado tecnologías para reducir las temperaturas de trabajo de manera de generar significativos ahorros de energía, menores emisiones y mayor nivel de seguridad en obra. Las mezclas que utilizan asfaltos modificados con polímeros o asfaltos especiales como ligantes hacen posible la reducción de las temperaturas de trabajo sin afectar significativamente las propiedades mecánicas y de adherencia. Sin embargo, cuando se fabrican mezclas con asfaltos convencionales la reducción de las temperaturas de trabajo implican directamente un importante desmedro de la calidad, aún cuando sea posible obtener las densidades de diseño. El presente estudio se enfoca en dos aditivos del tipo tensoactivos que fueron incorporados en diferentes tipos de cemento asfáltico para fabricar mezclas semicalientes (WMA), trabajando con sustanciales reducciones de temperatura, de 35 a 55oC. Los resul...

The oldest continuum-mechanics based approach to the numerical analysis of cracking masonry arches is due to Castigliano, 1879 [1, p. 472–478]. Castigliano analyzed the structural behaviour of Ponte Mosca, Turin (erected in 1834). He started with the assumption of a homogeneous, isotropic, elastic arch. After completing the analysis, Castigliano checked, for all radial joints, whether the joints were fully under compression or not. He assumed that the lack of tensile resistance of the mortared (or dry) joints dominates the behaviour of the masonry arch, so that the effective thickness of the arch is reduced to the height of the compressive zone (Fig. 1). In order to capture the mechanics of the arch correctly, it is therefore necessary to perform an iterative analysis. Due to the lack of tensile resistance, the centerline and the thickness of the arch change; the analysis is therefore repeated with the updated geometry, until the change to the preceding iteration is negligible. Cast...

Disponible en: http://redalyc.uaemex.mx/src/inicio/ArtPdfRed.jsp?iCve=75011517009 ... Redalyc Sistema de Información Científica Red de Revistas Científicas de América Latina, el Caribe, España y Portugal ... Zapata, Carlos Mario;González, Guillermo ESPECIFICACIÓN ...

This study investigated the crashworthiness performance of tubes filled simultaneously with cellular structures and pressurized air under quasi-static loading by considering the pressure, tube wall thickness, and deformation modes. The compression tests revealed an improvement in the crushing force response to the effects of the filler materials in the tube gap. The absorbed total energy increased by 2 and 3.8 times for pressurized and filled tubes concerning the empty tubes, respectively. It has been demonstrated that the interface effects between the cellular structure and the tube wall play a critical role in the pressure-filled tube’s deformation mode and energy absorption
capacity.

This article focuses on one of the steps proposed by the authors as a framework for improving the management of post-sale service. Specifically, the referred step tries to apply root cause analysis of failures to improve the organization of warranty support. This analysis can help make better decisions within the scope of after-sales service, for example, whether a particular incident should be treated under warranty or not. This article begins with an introduction to the current concept of warranty, briefly describing the proposed framework and the relevant literature related to such customer service. Thus, the reader can place the step to be developed in a context of useful tools and methodologies for the management of postsale service. Therefore, the main aspects of Root Cause Analysis are defined with the intention to apply these concepts in the management of those incidents reported by the user. With this objective, this article aims to adapt a developed and applied tool of the maintenance management (Root Cause Analysis) to a new field, in this case, the customer service. At the end of this article the main contributions for this work are summarized.

Exposición colectiva con los artistas NAHUEL AGÜERO, CANDELARIA FERNÁNDEZ COYA, SAMANTHA FERRO, GONZALO FREIGANES, NINA KUNAN, DANIEL LEBER, RENATA MOLINARI Y OSÍAS YANOV en El Mirador. Septiembre - octubre 2024.

Las intrincadas pirotecnologías de fundición de metales a partir de minerales constituyen procesos de transmutación que han logrado intrigar y embelesar a las más variadas sociedades. Para la arqueometalúrgia, este proceso entabla paralelismos con la reproducción humana y la fecundidad, la combinación de sangre y semen, y su transformación a través del calor de las relaciones sexuales. Acontece también un factor arcano, un saber esotérico que confiere la capacidad de mutar las materias. Y así, la metalurgia es también alquimia. De tal manera, comienza a evidenciarse una muy particular relación entre el manejo del metal, o bien, la destreza en la manipulación de las piedras, con la noción de poder.
La pregunta que da título a esta exposición busca revertir el proceso de la sublimación metálica y cuestionarse por cada uno de esos momentos, pases mágicos, técnicas, saberes y secretos que yacen en cada piedra. Una suerte de caldo primigenio hermético, un compendio de potencial esperando a ser impactado por la voluntad creadora.

This study investigates the mechanical and geometrical attributes of egg-box energy absorbing structures as crash safety barriers in the automotive industry. The research herein was originated from the earlier work of Prof. Shirvani, patented and further investigated by Cellbond Composites Ltd. who has invested in further research, for developing an analytical tool for geometric optimisation as an enhanced resolution to various shapes and materials. Energy absorption in egg-box occurs through plastic deformation of cell walls, examined through non-linear finite element simulations using ANSYS® and ANSYS/LS-DYNA® FE packages. Experimental dynamic crash tests have been designed to verify the validity of the FE simulations. Geometrical models are defined as 3D graphical representations, outlined in detail. Further, the impact behaviour of commercially pure aluminium egg-box energy absorbers is studied to identify the optimum design parameters describing the geometry of the structure. A simulation-based multi-objective optimisation strategy is employed to find a set of Pareto-optimal solutions where each solution represents a trade-off point with respect to the two conflicting objectives: the maximum impact force and the energy absorption capacity of the structure. The aim is to simultaneously minimise the former and maximise the latter, in the attempt to find purpose-specific optimal egg-box geometries. In light of the associated outcomes, it is shown that egg-box geometries with < ω), thin walls (t < 1mm), short inter-peak distances and small peak diameters. M-< ω), thin walls (t < 1mm), lengthy inter-peak distances and smaller peak diameters. It is concluded that, egg-box structures combined in the form of sandwich panels can be designed per application to act as optimised energy absorbers. Results of the proposed optimised sandwich structure are verified using analytical techniques.

The main purpose of this paper is to study the orthotropic plastic behaviour of the cold-rolled interstitial free steel HC260Y when it is submitted to various loading directions under monotonic tests. The experimental database included tensile tests carried out on specimens (in the as-received condition and after undergoing an annealing heat treatment) cut in different orientations according to the rolling direction. A model was proposed, depending on a plasticity criterion, a hardening law and an evolution law, which takes into account the anisotropy of the material. To validate the proposed identification strategy, a comparison with the experimental results of the planar tension tests, carried out on specimens cut parallel to the rolling direction, was considered. The obtained results allowed the prediction of the behaviour of this material when it is subjected to other solicitations whether simple or compound.

Class F flyash sample is subjected to roasting both by conventional process as well as microwave technique. The phase change during roasting with microwave heating has been investigated by XRD method and the chemical composition has been monitored continually by quantitative as well as AAS method. The results show that the flyash samples couple well with microwave and the temperature can reach approximately 10000 C in 7 minutes. The phase change in iron has been observed along with SiO2 and Al2O3. By proper control of the roasting temperature flyash can be sintered into a reasonably strong and relatively porous glassy ceramic material in a short period of time using microwave technique.