Nelson Arzola | Universidad Nacional de Colombia (National University of Colombia) (original) (raw)

Issue 191 by Nelson Arzola

The aim of this work was to study the behavior of sugarcane bagasse submitted to cutting, as a fu... more The aim of this work was to study the behavior of sugarcane bagasse submitted to cutting, as a function of its moisture content, angle of the blade edge and cutting speed. The specific cutting energy and peak cutting force were measured using an experimental facility developed for this series of experiments. An analysis of the results of the full factorial experimental design using a statistical analysis of variance (ANOVA) was performed. The response surfaces and empirical models for the specific cutting energy and peak cutting force were obtained using statistical analysis system software. Low angle of the blade edge and low moisture content are, in this order, the most important experimental factors in determining a low specific cutting energy and a low peak cutting force respectively. The best cutting conditions are achieved for an angle of blade edge of 20.8° and a moisture content of 10% w. b. The results of this work could contribute to the optimal design of sugarcane bagasse pre-treatment systems.

Papers by Nelson Arzola

Resources, 2022

The development of this research work seeks to determine the mechanical behavior of the compacted... more The development of this research work seeks to determine the mechanical behavior of the compacted mixture of pine sawdust and rice husk by varying the mass percentages of these biomasses obtained in briquettes, with the purpose of being marketed. The finite element software ANSYS is used to corroborate the results obtained for the samples named AIO, BIO and CIO with rice husk mass percentages of 25, 50 and 75, respectively. In the computational simulations, Young’s moduli of between 651 and 813 MPa and a Poisson’s ratio of 0.8 were found for all samples. In compression tests, Von Mises stresses of between 87 and 90 MPa and Von Mises strains between 0.09 and 0.12 m/m were found. Free-fall tests showed von Mises stresses below 4.24 MPa. It was determined that increasing the percentage of rice husk mass in the simulation models increased the value of Young’s modulus and compressive strength, this is a positive indication in relation to the strength of the formed briquettes, in case the...

Dyna, 2013

In this paper a procedure based on the Finite Element Method and Linear Elastic Fracture Mechanic... more In this paper a procedure based on the Finite Element Method and Linear Elastic Fracture Mechanics to obtain a mathematical model of crack propagation in transverse fillet welded joints is presented. We used ASTM-A36 steel plates and E6013 electrodes for the joints, using shielded metal arc welding (SMAW) as the welding process. The model uses a surface crack located in the weld toe. Differences of up to 41% in crack growth rates were found between cracks located 90% out of the bead mid plane with respect to the central crack. The straight and convex bead profiles were employed and according to the results there were no significant differences in fatigue life for both kinds of bead profiles. The results of the models were compared with conventional weld calculations and validated with experimental tests. The theoretical fatigue life values were within the statistical confidence interval for p=95%.

An approach for the evaluation of the mechanical performance of the bar and roller system of a st... more An approach for the evaluation of the mechanical performance of the bar and roller system of a steel bar bending machine is presented. It can be applied for design or retrofit purposes, with emphasis on the improvement of existent systems. The approach is illustrated for the case of a machine that has continuously lost its functionality due to fracture, surface fatigue, high power consumption and shape dimensions outside of specifications. The elastoplastic behavior of the bar is analyzed to determine the power consumption during the bending process. Moreover, the definition of the main design factors that govern the failure mechanisms in these components is carried out. A system of constraining equations is obtained, which is solved for a target function for the production capacity. Lastly, the enhanced redesign of the machine with new functional characteristics is presented.

DYNA, 2015

Ingeniería e Investigación, 2012

Waste-to-energy represents a challenge for the oil palm industry worldwide. Bio-pellet production... more Waste-to-energy represents a challenge for the oil palm industry worldwide. Bio-pellet production is an alternative way of adding value to oil palm biomass. This would mean that a product having major energy density becomes more mechanically stable and achieves better performance during combustion. This paper deals with oil palm shell pelleting; using binding agents having up to 25% mass keeping average particle size less than 1mm and moisture content up to 18.7% (d.b.) were evaluated. An experimental factorial design used binding agent mass percentage, milled shell particle size and moisture content as factors. Pellet density response surfaces and durability index were obtained. Pellet performance during thermal-chemical transformation was also evaluated by using thermogravimetry equipment. The results led to technical evaluation of scale-up at industrial production level.

Journal of Engineering Science and Technology Review, 2019

The current study investigates the influence of cutting speed and feed rate of the milling proces... more The current study investigates the influence of cutting speed and feed rate of the milling process on the surface finish and the uniaxial fatigue behavior of structural ASTM A 36 steel plates. A full factorial design is proposed that considers two levels for experimental factors cutting speed and feed rate. Fatigue tests are performed with a load rate R=0.04 and a frequency application of 12 Hz, using a total of 32 dog bone tensile test specimens. The surface quality is characterized by measuring the mean roughness (Ra), the mean roughness depth (Rz) and the maximum roughness depth (Rmax). After several analytic methods are made, it is shown that as the cutting speed increases, surface roughness decreases. In addition, a slower cutting speed during machining increases the probability of fatigue failure survival of the material. Likewise, a greater fatigue life was found as the maximum roughness decreases (Rmax).

Journal of Engineering Science and Technology Review

Journal of Mechanical Engineering and Sciences

This work proposes a finite element method model to predict lateral vibration phenomena arising i... more This work proposes a finite element method model to predict lateral vibration phenomena arising in the multi-stage rotor (seven stages) with unbalance, including damping and gyroscopic effects. The rotor dynamic analysis includes mathematical and experimental determination of the first and second critical speeds of the rotor and the assessment of the effects induced by the different unbalance combinations. The results show that while considering the unbalance effects in the impellers, critical speeds move to lower frequencies compared to normal conditions when the rotor is properly balanced. Finally, the results obtained analytically achieved a good degree of correspondence with experimental validation tests.

Revista Facultad de Ingeniería Universidad de Antioquia, Feb 21, 2020

This paper presents the development of theoretical and experimental models for the study of rotod... more This paper presents the development of theoretical and experimental models for the study of rotodynamic behavior of a multistage rotor. The transfer matrix method, which includes the characteristics of stiffness and damping for the supports and the stages respectively as well as the characteristics of unbalance in the stages, is used for the theoretical model. The data from a physical model was employed as a way of validating the theoretical results. The first two critical speeds were determined with the theoretical model and they differ in a low percentage with respect to the values measured experimentally. Moreover, the vibration level recorded in the physical model rises 2.5 times when the multistage rotor approaches the first two critical speeds. In addition to this, significant displacements of the lateral critical speeds are noticeable when an increase in mass imbalance is induced in several of the rotor impellers. RESUMEN: Este artículo presenta el desarrollo de modelos, teórico y experimental, para el estudio del comportamiento rotodinámico de un rotor multietapas. El modelo teórico se obtiene a partir de las ecuaciones de Lagrange y se resuelve empleando el método de la matriz de transferencia. En el análisis se incluyen las características de rigidez y amortiguamiento de los apoyos y de las diferentes etapas del rotor, así como el desbalance másico de estas últimas. Como vía de validación de los resultados teóricos se emplearon los datos provenientes de un modelo físico rotodinámico, especialmente desarrollado para la investigación. Las dos primeras velocidades críticas fueron determinadas con el modelo teórico y difieren en un bajo porcentaje con respecto a los valores medidos experimentalmente. Por otro lado, el nivel de vibración registrado en el modelo físico se eleva 2,5 veces cuando el rotor multietapas se aproxima a cualquiera de las primeras dos velocidades críticas. Adicionalmente, se describe un corrimiento apreciable en la magnitud de las velocidades críticas laterales cuando se aumenta el desbalance másico en varios de los impulsores del rotor.

INGENIERÍA Y COMPETITIVIDAD

Se realiza un estudio sobre la influencia de la desalineación de montaje en la vida de fatiga del... more Se realiza un estudio sobre la influencia de la desalineación de montaje en la vida de fatiga del árbol superior de los molinos de caña de azúcar. Se determina la razón de propagación de las grietas de fatiga en la sección más propensa a este tipo de falla, a partir del análisis de la variación de las cargas considerando la flotación del árbol superior durante la operación del molino. Es posible aumentar la vida de fatiga de los árboles empleando el procedimiento descrito, el cual determina un valor óptimo de desalineación de montaje. Para el molino estudiado se obtiene una desalineación de montaje óptima de valor igual a 1 mm por debajo del árbol de salida del reductor de baja. Para esta posición, el árbol superior alcanza una vida de fatiga de 1189 días de operación. Un análisis de vida de fatiga similar puede ser realizado para los árboles inferiores del molino

PLOS ONE

This article addresses the study of crack behavior elicited on axial fatigue in specimens joined ... more This article addresses the study of crack behavior elicited on axial fatigue in specimens joined by butt weld made of steel ASTM A36 by using fracture mechanics and simulation software of finite elements (Ansys APDL, Franc3D). The computational model was initially to define the geometry model by using CAD software. Specimens with Weld Reinforcement of 2 mm and 3mm were simulated. Subsequently, the type of element for the mesh, the information inclusion concerning material mechanical properties and load conditions were selected. By using Franc3D software, the crack propagation phenomenon is analyzed, and its growth parameters have been established. In this way, it is possible to calculate the magnitude of stress intensity factor (SIF) along the crack front. It is concluded that the stress located in the weld toe is maximized proportionately to the size of the weld reinforcement due to the concentration effect of geometric stress. In addition, it is observed that the propagation rate obtained from Paris law has a similar behavior for the studied weld reinforcements; the latter as there were short cracks.

Materials (Basel, Switzerland), Jan 5, 2018

The objective of this research is to develop an experimental-theoretical analysis about the influ... more The objective of this research is to develop an experimental-theoretical analysis about the influence of the cooling medium and the geometry of the welding bead profile in fatigue life and the associated parameters with structural integrity of welded joints. A welded joint with cruciform geometry is considered using SMAW (Shielded Metal ArcWelding), plates in structural steel ASTM A36 HR of 8 mm of thickness, and E6013 electrode input. A three-dimensional computational model of the cruciform joint was created using the finite element method. For this model, the surface undulation of the cord and differentiation in the mechanical properties of the fusion zone were considered, the heat-affected zone (HAZ) and base material, respectively. In addition, an initial residual stress field, which was established experimentally, was considered. The results were a set of analytical expressions for the weld magnification factor M. It was found that values for the latter decrease markedly in fun...

Materials (Basel, Switzerland), Jan 12, 2018

This research deals with the fatigue behavior of butt-welded joints, by considering the geometry ... more This research deals with the fatigue behavior of butt-welded joints, by considering the geometry and post-welding cooling cycles, as a result of cooling in quiet air and immersed in water. ASTM A-36 HR structural steel was used as the base metal for the shielded metal arc welding (SMAW) process with welding electrode E6013. The welding reinforcement was 1 mm and 3 mm, respectively; axial fatigue tests were carried out to determine the life and behavior in cracks propagation of the tested welded joints, mechanical characterization tests of properties in welded joints such as microhardness, Charpy impact test and metallographic analysis were carried out. The latter were used as input for the analysis by finite elements which influence the initiation and propagation of cracks and the evaluation of stress intensity factors (SIF). The latter led to obtaining the crack propagation rate and the geometric factor. The tested specimens were analyzed, by taking photographs of the cracks at its...

Journal of Physics: Conference Series

Revista Facultad De Ingenieria, Aug 16, 2013

Dyna, Jul 10, 2012

RESUMEN: Se presenta una revisión de varios modelos utilizados para explicar el comportamiento me... more RESUMEN: Se presenta una revisión de varios modelos utilizados para explicar el comportamiento mecánico del cartílago articular. La revisión hace énfasis en modelos mecánicos ya que los modelos físico químicos desbordan el alcance del análisis de sólidos que se quiere tratar. La mayoría de los modelos revisados retoman la idea planteada por Mow, la cual plantea que este tipo de tejidos puede ser modelado como un material bifásico, en donde cada fase tiene sus características específicas y la interacción entre ellas brinda las propiedades mecánicas del tejido como un global. El planteamiento de un modelo fenomenológico para el cartílago articular es complejo debido a la naturaleza de la respuesta bajo cargas transitorias y a los fenómenos físico químicos acoplados que tienen lugar. Los modelos futuros deberán estar orientados a considerar integralmente dichas características e interacciones.

Revista Facultad De Ingenieria Universidad De Antioquia, Jun 1, 2013