Edwin Alexis - Academia.edu (original) (raw)
Papers by Edwin Alexis
Universiteit Gent. Faculteit Ingenieurswetenschappen en Architectuur, 2020
xvii after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstru... more xvii after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstructure with graphite-ferrite interfaces, exhibiting a partially graphite spiky superficial morphology. The scratch test revealed that the ferrite-graphite interfaces with spiky nature exhibited a stronger resistance to delamination compared to the ferrite-graphite interfaces with smooth morphology. In brief: There were designed TMF setups closer to real engine conditions. The mechanical response was understood and compared with the literature. Furthermore, it was made a link between microstructure and mechanical properties leading to a complete understanding and description of TMF mechanical and microstructural behavior during crack initiation, propagation, and failure. Chapter 1 1 1 Chapter 1. Introduction "A journey of a thousand miles begins with a single step" Chinese proverb 1.1. Introduction he operational temperature of truck engines is pushed higher and higher in order to improve efficiency of fuel combustion, increase delivered power and comply with new international environmental standards. As a consequence, truck manufacturers are constantly looking for better performing engine materials. Particularly, the selection criteria for a material in the cylinder head aims to improve heat removal from the top of the combustion chamber (cf. Figure 1.1), whilst preserving optimum mechanical performance. Current engine cylinder head design incorporates four valve bores for each cylinder (see the circumscribed four largest bores in Figure 1.1), of which two are in charge of supplying the combustion chamber with fresh or even compressed air, and the other two are in charge of evacuating the hot combustion gases. Figure 1.1. Picture of a used cylinder head taken from the combustion chamber side (dark circular stain) showing four circumscribed circular bores for gas intake and removal. In the center a smaller bore is destinated for diesel injection. There are four valve bridge areas in-between the gas bores and outside the combustion chamber area and multiples bores for fastening systems. T Chapter 7 (Analysis of crack propagation of thermomechanical fatigue cracks by implementing 3D EBSD) focuses on the statistical aspects of the microstructural elements involved in crack propagation. Based on preliminary qualitative and quantitative 2D material descriptions (chapter 5), some crack propagation features are observed taking into account the 3D topology of the crack and its vicinity. It was found that when the crack propagates through the material it grows through the metallic matrix and along graphite particles. It is discussed which is the main crack propagation mechanism. A number of microstructural state variables are considered [2] G. Hutter, L. Zybell, and M. Kuna, "Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies-A review," Eng.
Mediante proyección térmica de arco eléctrico, fueron depositados con las condiciones ambientales... more Mediante proyección térmica de arco eléctrico, fueron depositados con las condiciones ambientales de Cartagena de Indias tres materiales comercialmente conocidos como 140MXC, 530AS y 560AS, sobre acero AISI/SAE 4340. Con el objetivo de evaluar la mejor estrategia para preservar la resistencia a la corrosión y al desgaste del sistema capa-sustrato los recubrimientos fueron depositados de tres formas: (1) Monocapas homogéneas de cada material; (2) Bicapas compuestas de una monocapa de 140MXC sobre una de 530AS o de 560AS y (3) recubrimientos tipo monocapas disimiles utilizando dos materiales simultáneamente 140MXC+530AS en el primer caso y 140MXC+560AS en el segundo caso. La resistencia a la corrosión y al desgaste fue evaluada mediante ensayos de polarización potenciodinamica, espectroscopia de impedancia electroquímica y desgaste abrasivo con arena seca y rueda con caucho. La caracterización estructural y morfológica se realizó mediante microscopía óptica, microscopia laser confocal, microscopia electrónica de barrido, microscopia electrónica de transmisión, difracción de electrones, difracción de rayos X y micro dureza. Fue encontrado que el recubrimiento llamado 140MXC posee dureza de alrededor de 10GPa y que se depositó con estructura de matriz amorfa que embebe nanocristales, esto fue encontrado mediante microscopia electrónica de transmisión, además su combinación en monocapas disimiles produjo seudoaleaciones en las que las tasas de desgaste fueron ligeramente superiores a las del 140MXC y estas fueron las menores tasa de todo el estudio. Por otra parte los productos de corrosión posiblemente causaron que los depósitos tipo bicapa incrementaran su resistencia a la polarización con respecto al tiempo, debido a taponamiento de defectos estructurales como poros y grietas interconectados. Los resultados de corrosión y desgaste, así como los mecanismos de falla se describen en esta investigación. / Abstract: Using thermal spray wire arc were deposited with atmospheric condition of Cartagena de Indias three materials commercially known as 140MXC, 530AS and 560AS, above steel AISI / SAE 4340. With the aim to evaluate the best strategy for preserving the corrosion and wear resistance of the system coating-substrate; Coatings were deposited in three ways: (1) homogeneous single layers of each material, (2) bilayers consist of a monolayer of 140MXC above 530AS or 560AS and (3) type monolayer coatings using two different materials 140MXC + 530AS in the first case and 140MXC + 560AS in the second case, the corrosion and wear resistance was evaluated by potentiodynamic polarization test, spectroscopy electrochemical impedance and abrasive wear with dry sand rubber wheel, on the other hand, the structural and morphological characterization were made by, optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and hardness; Were found that the coating call 140MXC has a hardness of 10GPa. and was deposited with an amorphous structure that inbedts nano crystals, also it combination at single layers produced pseudo-alloys in which the wear resistance was lightly greater than 140MXC, and those was the best wear rates of all the investigation. On the other hand the corrosion products possibly caused the bilayers increased the polarization resistance with time, due to the clogging of structural defects connected as cracks and pores. The corrosion and wear results and failure mechanisms are described in this research.Maestrí
Proposito y Metodo del Estudio: Las microalgas son microorganismos muy versatiles, capaces de apr... more Proposito y Metodo del Estudio: Las microalgas son microorganismos muy versatiles, capaces de aprovechar los nutrientes de aguas residuales, causantes de problemas tales como la eutrofizacion. Asociado a esto tienen la habilidad de sintetizar productos de interes comerciales de alto valor (PCAV) tales como; proteinas, acidos grasos, precursores de vitaminas, carotenoides entre otros. Sin embargo, para acumular cantidades importantes de estos productos es necesario inducir a las celulas a estres ambiental. Esta investigacion tuvo como objetivo la identificacion de PCAV en la biomasa del consorcio de microalgas BR-UANL-01 nativo del estado de Nuevo Leon, siguiendo las bases de la economia circular propuesta por la ONU, en los Objetivos del Desarrollo Sostenible para 2030. Contribuciones y Conclusiones: El consorcio BR-UANL-01 fue reactivado en agua residual tratada, la cual sirvio como medio de crecimiento, durante la reactivacion el pH fue monitoreado. Ademas, se lograron identificar...
Universiteit Gent. Faculteit Ingenieurswetenschappen en Architectuur, 2020
xvii after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstru... more xvii after annealing, a certain pearlite fraction decomposed into Fe and C, producing a microstructure with graphite-ferrite interfaces, exhibiting a partially graphite spiky superficial morphology. The scratch test revealed that the ferrite-graphite interfaces with spiky nature exhibited a stronger resistance to delamination compared to the ferrite-graphite interfaces with smooth morphology. In brief: There were designed TMF setups closer to real engine conditions. The mechanical response was understood and compared with the literature. Furthermore, it was made a link between microstructure and mechanical properties leading to a complete understanding and description of TMF mechanical and microstructural behavior during crack initiation, propagation, and failure. Chapter 1 1 1 Chapter 1. Introduction "A journey of a thousand miles begins with a single step" Chinese proverb 1.1. Introduction he operational temperature of truck engines is pushed higher and higher in order to improve efficiency of fuel combustion, increase delivered power and comply with new international environmental standards. As a consequence, truck manufacturers are constantly looking for better performing engine materials. Particularly, the selection criteria for a material in the cylinder head aims to improve heat removal from the top of the combustion chamber (cf. Figure 1.1), whilst preserving optimum mechanical performance. Current engine cylinder head design incorporates four valve bores for each cylinder (see the circumscribed four largest bores in Figure 1.1), of which two are in charge of supplying the combustion chamber with fresh or even compressed air, and the other two are in charge of evacuating the hot combustion gases. Figure 1.1. Picture of a used cylinder head taken from the combustion chamber side (dark circular stain) showing four circumscribed circular bores for gas intake and removal. In the center a smaller bore is destinated for diesel injection. There are four valve bridge areas in-between the gas bores and outside the combustion chamber area and multiples bores for fastening systems. T Chapter 7 (Analysis of crack propagation of thermomechanical fatigue cracks by implementing 3D EBSD) focuses on the statistical aspects of the microstructural elements involved in crack propagation. Based on preliminary qualitative and quantitative 2D material descriptions (chapter 5), some crack propagation features are observed taking into account the 3D topology of the crack and its vicinity. It was found that when the crack propagates through the material it grows through the metallic matrix and along graphite particles. It is discussed which is the main crack propagation mechanism. A number of microstructural state variables are considered [2] G. Hutter, L. Zybell, and M. Kuna, "Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies-A review," Eng.
Mediante proyección térmica de arco eléctrico, fueron depositados con las condiciones ambientales... more Mediante proyección térmica de arco eléctrico, fueron depositados con las condiciones ambientales de Cartagena de Indias tres materiales comercialmente conocidos como 140MXC, 530AS y 560AS, sobre acero AISI/SAE 4340. Con el objetivo de evaluar la mejor estrategia para preservar la resistencia a la corrosión y al desgaste del sistema capa-sustrato los recubrimientos fueron depositados de tres formas: (1) Monocapas homogéneas de cada material; (2) Bicapas compuestas de una monocapa de 140MXC sobre una de 530AS o de 560AS y (3) recubrimientos tipo monocapas disimiles utilizando dos materiales simultáneamente 140MXC+530AS en el primer caso y 140MXC+560AS en el segundo caso. La resistencia a la corrosión y al desgaste fue evaluada mediante ensayos de polarización potenciodinamica, espectroscopia de impedancia electroquímica y desgaste abrasivo con arena seca y rueda con caucho. La caracterización estructural y morfológica se realizó mediante microscopía óptica, microscopia laser confocal, microscopia electrónica de barrido, microscopia electrónica de transmisión, difracción de electrones, difracción de rayos X y micro dureza. Fue encontrado que el recubrimiento llamado 140MXC posee dureza de alrededor de 10GPa y que se depositó con estructura de matriz amorfa que embebe nanocristales, esto fue encontrado mediante microscopia electrónica de transmisión, además su combinación en monocapas disimiles produjo seudoaleaciones en las que las tasas de desgaste fueron ligeramente superiores a las del 140MXC y estas fueron las menores tasa de todo el estudio. Por otra parte los productos de corrosión posiblemente causaron que los depósitos tipo bicapa incrementaran su resistencia a la polarización con respecto al tiempo, debido a taponamiento de defectos estructurales como poros y grietas interconectados. Los resultados de corrosión y desgaste, así como los mecanismos de falla se describen en esta investigación. / Abstract: Using thermal spray wire arc were deposited with atmospheric condition of Cartagena de Indias three materials commercially known as 140MXC, 530AS and 560AS, above steel AISI / SAE 4340. With the aim to evaluate the best strategy for preserving the corrosion and wear resistance of the system coating-substrate; Coatings were deposited in three ways: (1) homogeneous single layers of each material, (2) bilayers consist of a monolayer of 140MXC above 530AS or 560AS and (3) type monolayer coatings using two different materials 140MXC + 530AS in the first case and 140MXC + 560AS in the second case, the corrosion and wear resistance was evaluated by potentiodynamic polarization test, spectroscopy electrochemical impedance and abrasive wear with dry sand rubber wheel, on the other hand, the structural and morphological characterization were made by, optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and hardness; Were found that the coating call 140MXC has a hardness of 10GPa. and was deposited with an amorphous structure that inbedts nano crystals, also it combination at single layers produced pseudo-alloys in which the wear resistance was lightly greater than 140MXC, and those was the best wear rates of all the investigation. On the other hand the corrosion products possibly caused the bilayers increased the polarization resistance with time, due to the clogging of structural defects connected as cracks and pores. The corrosion and wear results and failure mechanisms are described in this research.Maestrí
Proposito y Metodo del Estudio: Las microalgas son microorganismos muy versatiles, capaces de apr... more Proposito y Metodo del Estudio: Las microalgas son microorganismos muy versatiles, capaces de aprovechar los nutrientes de aguas residuales, causantes de problemas tales como la eutrofizacion. Asociado a esto tienen la habilidad de sintetizar productos de interes comerciales de alto valor (PCAV) tales como; proteinas, acidos grasos, precursores de vitaminas, carotenoides entre otros. Sin embargo, para acumular cantidades importantes de estos productos es necesario inducir a las celulas a estres ambiental. Esta investigacion tuvo como objetivo la identificacion de PCAV en la biomasa del consorcio de microalgas BR-UANL-01 nativo del estado de Nuevo Leon, siguiendo las bases de la economia circular propuesta por la ONU, en los Objetivos del Desarrollo Sostenible para 2030. Contribuciones y Conclusiones: El consorcio BR-UANL-01 fue reactivado en agua residual tratada, la cual sirvio como medio de crecimiento, durante la reactivacion el pH fue monitoreado. Ademas, se lograron identificar...