On Damage Characterization of a Steel Sheet

Ductile damage is a physical phenomena which involves progressive deterioration of mechanical properties of metals, when undergoing high deformations. Compared to plasticity, the physical mechanisms behind damage are more complex and the microscale is not longer negligible. In mathematical damage models, founding an optimal set of material parameters can be a hard task due to the strong coupling and non-linearity of the equations. An identification strategy is then crucial to arrive to a general set of parameters. Therefore, we address the fully characterization of a ferritic steel sheet, involving the elasto-plastic and damage parameters. This poster presents an hybrid experimental-numerical procedure, coupling numerical simulations, optimization algorithms and digital image correlation measurements, over a set of representative experimental and numerical results of tensile, shear and plane strain tests in different material directions. Due to the small thickness of the sheet, the constitutive model is very prone to localization into a shear band difficulting the damage parameters identification. It is found that a porosity induced inhomogeneity plus a mixed hardening can delay localization and represent the entire deformation range of the tests, leading to acceptable results. Different set of parameters are also obtained and then validated with experimental results. This localization phenomena should be carefully considered in applications involving complex strain paths

Experimental and Numerical Characterization of Damage and Application to Incremental Forming

Nowadays, product manufacturing can be divided into two groups: relatively simple products produced in a large production chain and complex (specialized) components produced in reduced batches. Within the second group, prototyping through incremental sheet forming (ISF) has been subject of several studies. ISF refers to processes where the plastic deformation occurs by repeated contact with a relatively small tool. A crucial aspect in the ISF processes is that the final shape is determined only by the tool movement. The focus of this research is the single point incremental forming (SPIF) process variant, where a clamped sheet metal is deformed by using a relatively small spherical tool. SPIF has several advantages over traditional forming, such as the high formability attainable by the material. Different hypothesis haven been proposed to explain this behavior, but there is still not a clear and definitive understanding of the relation between the particular stress and strain state induced in the material during SPIF and the material degradation leading to localization or fracture. In this thesis, a fundamental research is proposed using the finite element (FE) code LAGAMINE, developed within the University of Liège. Numerical implementation and validation of the Gurson-Tvergaard-Needleman (GTN) damage model into this FE code is performed. An experimental test campaign is developed to characterize plastic and damage behavior and to validate the damage model for the DC01 steel grade. Finally, this damage model is applied to simulate the SPIF process in order to verify if it is capable to predict failure. The thesis discusses the material parameter identification for classical plasticity models, describing the anisotropy and hardening behavior of the sheet metal. The derivation of the equations of the numerical damage model and the efficiency of the implementation is presented in great detail. A methodology for the numerical parameter identification of the damage model is proposed, including microscopic measurements by optical microscopy and strain and displacement field measurements by digital image correlation (DIC). The identified Gurson model is applied to simulate standard SPIF geometries, like the line, cone and pyramid tests. The simulations are performed using the solid-shell element formulation and validated in terms of shape and force prediction. Literature reviews of the Gurson model and the SPIF process are also included. The experimental results show that the selected material (DC01 steel sheet) exhibits a slight anisotropic behavior and work-hardening stagnation on cyclic tests. The performed microscopic measurements are not representative of the actual damage, but they give a qualitative estimation of the physical mechanism of fracture. The initial porosity of the material was determined using optical microscopy measurements in the base material. The numerical implementation of the model is developed with all variables integrated in an implicit way, based on the backward Euler scheme. Nucleation, coalescence and shear extensions implementations are validated by results obtained from the literature. The macroscopic campaign allowed to identify the parameters for nucleation, coalescence and shear. An unique set of results matching all experiments was not possible to obtain, so different sets of parameters are retrieved following an approach that includes inverse modeling and sensitivity analysis. A numerical-experimental comparison of strain values in the loading direction shows that the model is able to correctly predict the strain distribution except during localization of the strain. Globally, the obtained set of material parameters is in good agreement with the experimental results. For SPIF FE simulations, the results of the shape prediction are in good agreement with the experimental results, both for the line and pyramid test. Nevertheless, the force prediction is too high compared to reference values. On the other hand, the GTN model is capable to detect failure in a pyramid and a cone, but the prediction is too premature compared to the experimental failure angle for the same material and geometry. An accurate prediction of failure for the SPIF process was not possible to achieve. The GTN model extended to shear presents inherent flaws that prevent an accurate prediction of the failure angle for the SPIF process. Hence, an extensive research on the damage mechanisms leading to fracture for SPIF cannot rely (only) on the GTN model. The classical coalescence model of the GTN model is insufficient to correctly predict failure. Hence, it is recommended that further analysis concentrates on the description of this particular stage of damage evolution. During the development of this thesis, a robust implementation of the GTN model into the FE code LAGAMINE was done, including an extensive experimental database of microscopic and macroscopic measurements for the DC01 steel sheet. Other phenomena can be explored thanks to this model

Técnicas y métodos para el seguimiento de la evolución de la habilidad motriz fina de miembro superior : revisión de la literatura

Introduction: This review article is the product of research on the methods, techniques and devices used in the measurement of fine motor skills of upper limbs and its respective evolution, developed at Universidad del Cauca in 2018. Problem: Objective measurement of the evolution of upper limb motor skills in the rehabilitation processes.  Objective: To identify the conventional techniques and electronic devices used in the measurement of the evolution of upper limb motor ability.  Methodology: Four scientific databases were reviewed in addition to the Google Scholar search engine. The keywords used for the search were: "fine motor skills", "hand measurement", "hand rehabilitation"and "hand function", among others.  Results: Approximately 3840 articles related to the subject were found. When applying the exclusion criteria, the article number to be revised was reduced to 63, which were analyzed in the present review. Conclusions: The tools applied by health professionals are convenient due to their rapid execution and easy access, however they can be subject to human error since they depend on the experience of the user. Electronic systems present objective measurements, however, their complexity and cost are high. Originality: This work presents information on the therapeutic techniques and technological devices used, in certain pathologies, for the evaluation of upper limb motor ability. Limitations: Not all articles analyzed have a detailed description of the people in which the studies were conducted.Introducción: El artículo es producto de una investigación sobre los métodos, técnicas y dispositivos utilizados en la medición de la habilidad motriz fina de miembro superior y su respectiva evolución, desarrollada en la Universidad del Cauca en el año 2018. Problema: Medición objetiva la evolución de la habilidad motriz de miembro superior en los procesos de rehabilitación. Objetivo: Identificar las técnicas convencionales y dispositivos electrónicos utilizados en la medición de la evolución de la habilidad motriz de miembro superior. Metodología: Se revisaron cuatro bases de datos científicas además del motor de búsqueda Google Académico. Para la búsqueda se utilizaron las palabras clave: “fine motor skills”, “hand measurement”, “hand rehabilitation”, “hand function”, entre otras. Resultados: Se encontraron aproximadamente 3840 artículos relacionados con la temática. Al aplicar los criterios de exclusión el número de artículo a revisar se redujo a 63, los cuales fueron analizados en la presente revisión. Conclusiones: Las herramientas aplicadas por profesionales de la salud son convenientes debido a su rápida ejecución y fácil acceso, sin embargo pueden estar sujetas al error humano puesto que dependen de la experiencia de quien las utiliza. Los sistemas electrónicos, presentan mediciones objetivas, no obstante, su complejidad y costo es elevado. Originalidad: Este trabajo presenta información sobre las técnicas terapéuticas y dispositivos tecnológicos, utilizados en ciertas patologías, para la evaluación de la habilidad motriz de miembro superior. Limitaciones: No todos los artículos analizados cuentan con una descripción detallada de las personas en las que los estudios fueron realizados

Técnicas y métodos para el seguimiento de la evolución de la habilidad motriz fina de miembro superior : revisión de la literatura

Introduction: This review article is the product of research on the methods, techniques and devices used in the measurement of fine motor skills of upper limbs and its respective evolution, developed at Universidad del Cauca in 2018. Problem: Objective measurement of the evolution of upper limb motor skills in the rehabilitation processes.  Objective: To identify the conventional techniques and electronic devices used in the measurement of the evolution of upper limb motor ability.  Methodology: Four scientific databases were reviewed in addition to the Google Scholar search engine. The keywords used for the search were: "fine motor skills", "hand measurement", "hand rehabilitation"and "hand function", among others.  Results: Approximately 3840 articles related to the subject were found. When applying the exclusion criteria, the article number to be revised was reduced to 63, which were analyzed in the present review. Conclusions: The tools applied by health professionals are convenient due to their rapid execution and easy access, however they can be subject to human error since they depend on the experience of the user. Electronic systems present objective measurements, however, their complexity and cost are high. Originality: This work presents information on the therapeutic techniques and technological devices used, in certain pathologies, for the evaluation of upper limb motor ability. Limitations: Not all articles analyzed have a detailed description of the people in which the studies were conducted.Introducción: El artículo es producto de una investigación sobre los métodos, técnicas y dispositivos utilizados en la medición de la habilidad motriz fina de miembro superior y su respectiva evolución, desarrollada en la Universidad del Cauca en el año 2018. Problema: Medición objetiva la evolución de la habilidad motriz de miembro superior en los procesos de rehabilitación. Objetivo: Identificar las técnicas convencionales y dispositivos electrónicos utilizados en la medición de la evolución de la habilidad motriz de miembro superior. Metodología: Se revisaron cuatro bases de datos científicas además del motor de búsqueda Google Académico. Para la búsqueda se utilizaron las palabras clave: “fine motor skills”, “hand measurement”, “hand rehabilitation”, “hand function”, entre otras. Resultados: Se encontraron aproximadamente 3840 artículos relacionados con la temática. Al aplicar los criterios de exclusión el número de artículo a revisar se redujo a 63, los cuales fueron analizados en la presente revisión. Conclusiones: Las herramientas aplicadas por profesionales de la salud son convenientes debido a su rápida ejecución y fácil acceso, sin embargo pueden estar sujetas al error humano puesto que dependen de la experiencia de quien las utiliza. Los sistemas electrónicos, presentan mediciones objetivas, no obstante, su complejidad y costo es elevado. Originalidad: Este trabajo presenta información sobre las técnicas terapéuticas y dispositivos tecnológicos, utilizados en ciertas patologías, para la evaluación de la habilidad motriz de miembro superior. Limitaciones: No todos los artículos analizados cuentan con una descripción detallada de las personas en las que los estudios fueron realizados

Técnicas y métodos para el seguimiento de la evolución de la habilidad motriz fina de miembro superior : revisión de la literatura

Introduction: This review article is the product of research on the methods, techniques and devices used in the measurement of fine motor skills of upper limbs and its respective evolution, developed at Universidad del Cauca in 2018. Problem: Objective measurement of the evolution of upper limb motor skills in the rehabilitation processes.  Objective: To identify the conventional techniques and electronic devices used in the measurement of the evolution of upper limb motor ability.  Methodology: Four scientific databases were reviewed in addition to the Google Scholar search engine. The keywords used for the search were: "fine motor skills", "hand measurement", "hand rehabilitation"and "hand function", among others.  Results: Approximately 3840 articles related to the subject were found. When applying the exclusion criteria, the article number to be revised was reduced to 63, which were analyzed in the present review. Conclusions: The tools applied by health professionals are convenient due to their rapid execution and easy access, however they can be subject to human error since they depend on the experience of the user. Electronic systems present objective measurements, however, their complexity and cost are high. Originality: This work presents information on the therapeutic techniques and technological devices used, in certain pathologies, for the evaluation of upper limb motor ability. Limitations: Not all articles analyzed have a detailed description of the people in which the studies were conducted.Introducción: El artículo es producto de una investigación sobre los métodos, técnicas y dispositivos utilizados en la medición de la habilidad motriz fina de miembro superior y su respectiva evolución, desarrollada en la Universidad del Cauca en el año 2018. Problema: Medición objetiva la evolución de la habilidad motriz de miembro superior en los procesos de rehabilitación. Objetivo: Identificar las técnicas convencionales y dispositivos electrónicos utilizados en la medición de la evolución de la habilidad motriz de miembro superior. Metodología: Se revisaron cuatro bases de datos científicas además del motor de búsqueda Google Académico. Para la búsqueda se utilizaron las palabras clave: “fine motor skills”, “hand measurement”, “hand rehabilitation”, “hand function”, entre otras. Resultados: Se encontraron aproximadamente 3840 artículos relacionados con la temática. Al aplicar los criterios de exclusión el número de artículo a revisar se redujo a 63, los cuales fueron analizados en la presente revisión. Conclusiones: Las herramientas aplicadas por profesionales de la salud son convenientes debido a su rápida ejecución y fácil acceso, sin embargo pueden estar sujetas al error humano puesto que dependen de la experiencia de quien las utiliza. Los sistemas electrónicos, presentan mediciones objetivas, no obstante, su complejidad y costo es elevado. Originalidad: Este trabajo presenta información sobre las técnicas terapéuticas y dispositivos tecnológicos, utilizados en ciertas patologías, para la evaluación de la habilidad motriz de miembro superior. Limitaciones: No todos los artículos analizados cuentan con una descripción detallada de las personas en las que los estudios fueron realizados

Towards fracture prediction in single point incremental forming

peer reviewedThe stress state in metal forming processes usually implies low values of triaxiality. It is well known that damage models based only on triaxiality fails to capture the damage behavior properly, and recent articles have stressed the effect of the Lode parameter in describing damage. Moreover, in some process like incremental forming, the through thickness shear could dominate the rupture mechanism making the description, using solely the triaxiality, inaccurate. In this paper, a preliminary study of the stress state is carried over a near-to-failure single point incremental forming (SPIF) formed cone, through finite elements simulations using a newly developed solid-shell element. The results provide a basis for further studies into damage development in SPIF

Estudio de asfaltos y mezclas asfálticas modificadas con aceite residual de motor

Trabajo de investigaciónLos avances en infraestructura vial son muy importantes para el desarrollo socioeconómico de un país, a su vez, teniendo en cuenta las características ambientales en las que se encuentra sumergido el mundo es importante idear estrategias que permitan el progreso en infraestructura aportando de manera significativa al medio ambiente. El uso de aceite residual de motor como modificante del asfalto es una alternativas que se plantean actualmente como linea de investigación.INTRODUCCIÓN 1. GENERALIDADES 2. MARCO REFERENCIAL 3. METODOLOGIA 4. ANALISIS DE RESULTADOS 5. CONCLUSIONES Y RECOMENDACIONES BIBLIOGRAFÍA ANEXOSEspecializaciónEspecialista en Ingeniería de Pavimento