Módulos elásticos equivalentes para predicción de deformaciones en articulaciones (original) (raw)
Related papers
Modelo Elastoplástico para Medios Cohesivos Friccionales Parcialmente Saturados
1999
Los suelos parcialmente saturados se consideran como medios porosos conformado por tres fases : solida , liquida y gaseosa. La deformacion de un suelo de este tipo es debida tanto a la variacion de su estado tensional como a la variacion del contenido de humedad. En este trabajo se formula un modelo constitutivo elastoplastico para materiales cohesivos friccionales en el cual se incorpora como componentes tensionales adicionales, la presion neta total y la variacion de la succion. Estas se aplican al modelo basado en un criterio de falla de tipo cono-capa, de tres invariantes propuesto originalmente por Sture , Macari y Runesson (MRS-Lade model).
Contribuição à obtenção do módulo de elasticidade do concreto utilizando modelagem micromecânica
Revista IBRACON de Estruturas e Materiais, 2011
Expressões presentes nas normas nacionais e internacionais relacionam o módulo de elasticidade do concreto com a resistência à compressão. O concreto, considerado como material compósito trifásico, tem suas propriedades elásticas diretamente influenciadas pela zona de transição (ITZ), a qual é caracterizada por sua maior porosidade em relação à pasta de cimento. Modelos de micromecânica como os de Mori-Tanaka e esfera de três fases podem ser aplicados com bons resultados quando utilizados para a análise do concreto. Este trabalho apresenta um estudo sobre o comportamento evolutivo do módulo de elasticidade do concreto, tal estudo é feito mediante a aplicação das expressões normativas e de modelos de micromecânica. Comparado-se com os valores experimentais produzidos percebe-se uma boa concordância quando a modelagem micromecânica leva em conta a ITZ. Também é confirmada a qualidade das expressões da NBR 6118:2003 e do CEB-90.
Elasticity in Elastics-An in-vitro study
PubMed, 2014
Background: Orthodontic tooth movement results from application of forces to teeth. Elastics in orthodontics have been used both intra-orally and extra- orally to a great effect. Their use, combined with good patient co-operation provides the clinician with the ability to correct both anteroposterior and vertical discrepancies. Force decay over a period of time is a major problem in the clinical usage of latex elastics and synthetic elastomers. This loss of force makes it difficult for the clinician to determine the actual force transmitted to the dentition. It's the intent of the clinician to maintain optimal force values over desired period of time. The majority of the orthodontic elastics on the market are latex elastics. Since the early 1990s, synthetic products have been offered in the market for latex-sensitive patients and are sold as nonlatex elastics. There is limited information on the risk that latex elastics may pose to patients. Some have estimated that 0.12-6% of the general population and 6.2% of dental professionals have hypersensitivity to latex protein. There are some reported cases of adverse reactions to latex in the orthodontic population but these are very limited to date. Although the risk is not yet clear, it would still be inadvisable to prescribe latex elastics to a patient with a known latex allergy. To compare the in-vitro performance of latex and non latex elastics. Materials & methods: Samples of 0.25 inch, latex and non latex elastics (light, medium, heavy elastics) were obtained from three manufacturers (Forestadent, GAC, Glenroe) and a sample size of ten elastics per group was tested. The properties tested included cross sectional area, internal diameter, initial force generated by the elastics, breaking force and the force relaxation for the different types of elastics. Force relaxation testing involved stretching the elastics to three times marketed internal diameter (19.05 mm) and measuring force level at intervals over a period of 48 hours. The data were analyzed with student independent - t test, analysis of variance and the Tukey - HSD test at p <0.05 level of significance. Results: Non latex elastics had greater cross sectional area than latex elastics in all types of elastics. Forestadent heavy elastics had grater cross sectional area than GAC and Glenroe. There was no statistically significant difference in the internal diameter in between all type of elastics. Forestadent non latex elastics had greater breaking force compared to GAC and Glenroe elastics. Forces generated by the elastics decreased over 48 hours to an average load approximating 65-75% of the manufacturer's values. Force degradation was greater in non latex elastics compared to latex elastics. Conclusion: The results of the study demonstrated that the clinical choice of elastics should be based on the patient's medical history and the specific mechanical properties of the type of elastic. How to cite the article: Kamisetty SK, Nimagadda C, Begam MP, Nalamotu R, Srivastav T, Shwetha GS. Elasticity in Elastics-An in-vitro study. J Int Oral Health 2014;6(2):96-105.
A Comparison of Elastic Constants of Different Biological Tissues
This study presents the data on comparison of elastic constants of different biological and non-biological materials reported in the literature along with the values determined for bovine bone scpula, rib and femur in the present investigation for the purpose of comparison. The values of elastics constants are high for bone when compared with soft tissues and other hard calcified integument materials. However, significant variation is not observed in Poisson's ration of soft (human lens capsule: 0.47) and hard calcified derivatives of the integument (about 0.35), with respect to bone. The significant variations in the elastic constants such as Young's modulus, rigidity modulus and bulk modulus of different bone samples, even in the same bone are attributed to molecular composition, both organic and inorganic, and the water present in the pores, bound to collagen and in the mineral crystallites of the bone tissues. It is evident from the data that the Young’s modulus for rib and femur is more than that of scpula by two fold, whereas the rigidity modulus by three fold. The value of bulk modulus is double to that of rib and femur. Poisson’s ratio is more in scapula, less in femur and in between for the rib.
Modelación y análisis de susceptibilidad a la deformación permanente de mezclas asfálticas
Revista ingeniería de construcción, 2011
La deformación permanente de mezclas asfálticas del Área Metropolitana del Valle de Aburra-Antioquia, las cuales se fabrican en nuestro medio bajo las especificaciones INVIAS (Instituto Nacional de Vías) y del Valle de Aburrá, se estudiaron utilizando un modelo constitutivo propuesto anteriormente. Este modelo mostró previamente ser efectivo en predecir la deformación de mezclas asfálticas en el Reino Unido bajo diferentes tipos de carga bajo condiciones uniaxiales y triaxiales, y temperaturas comprendidas entre 0 ºC y 40 ºC. Para el caso de las mezclas del Valle de Aburrá se emplearon temperaturas en un intervalo de 20 ºC a 50 ºC y se implementó el modelo propuesto con el fin de predecir la susceptibilidad a la deformación permanente. Mediante el estudio experimental de las mezclas se encontró que el comportamiento de estado estable de estas siguió el modelo modificado de Cross 2 (Wang, 2011), con las mezclas exhibiendo comportamiento viscoso lineal y no-lineal a bajos y altos niveles de esfuerzos, respectivamente. Tanto para condiciones de carga como de recuperación se observó una dependencia de la temperatura en el material que fue adecuadamente predicha por el modelo de Arrhenius 3 bajo el intervalo de temperaturas estudiado. Al realizar la modelación del comportamiento de las mezclas se encontró que el modelo propuesto por Ossa et al. (2010) aplica a las mezclas estudiadas y se determinó que la susceptibilidad a la deformación de estas varía considerablemente dependiendo de los materiales utilizados por el productor y en especial el agregado empleado, a pesar de ser mezclas teóricamente similares.
MATEC Web of Conferences
The purpose of this paper is to critically review and address the cause of variation in the values of elastic modulus (E) of bone. Properties used for materials (especially) bones is one of the crucial factors in modeling and simulation experiments with sensitive procedures such as Finite Elements. The values of elastic modulus acquired from secondary databases, literature and online repositories differ in many ways. This is due to an underlying fact that different methods are used for one definite set of species and vice versa. According to a human understanding, this might bar the perceptive of use of elastic modulus in the research when (especially) insightful procedures are in question for example Finite Element Analysis (FEA) of materials with sensitive procedures. The means and the methods, through which the values are obtained, do not follow a standard methodology. Thus, this area needs attention. Despite the advances in technology and state-of-the-art methods in the field of biomechanics and biomedical engineering there is a need to formulate a standard method which can produce reliable set of E-values. Through this paper, we seek to raise an important scientific question as to what systemic methodology should be adapted to achieve a value of elastic modulus that is not only reliable, but reasonable as well. The paper also, focus briefly on the sources of error responsible for this variation and the significance of elastic modulus values in important numerical methods such as Finite Elements (FE).
Avaliação in vitro da força liberada por elásticos em cadeia
Dental Press Journal of Orthodontics, 2011
OBJETIVO: avaliar in vitro e comparar a redução de intensidade das forças liberadas por três grupos de elásticos em cadeia, com diferentes configurações, de um mesmo fabricante, medidas em intervalos de tempo preestabelecidos. MÉTODOS: os segmentos de elásticos em cadeia foram alongados e mantidos ativados durante o experimento com o auxílio de um dispositivo desenvolvido especialmente para esse fim e para possibilitar a leitura das forças. A avaliação da degradação da força foi realizada medindo-se a intensidade da força ao longo do tempo, e calculando-se o percentual de força perdida em relação à força inicial, em cada intervalo de tempo e para cada amostra testada. RESULTADOS E CONCLUSÕES: os dados coletados foram submetidos a análises estatísticas e os resultados demonstraram que, nos momentos seguintes ao inicial, a intensidade da força variou, dentro dos grupos e entre os grupos, nos diferentes momentos. A leitura dos valores das forças remanescentes em cada momento, comparada...