Examinando por Materia "Loading condition"

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    A survey on static and quasi-static finite element models of the human cervical spine
    (Springer-Verlag France, 2018-05-01) Suarez-Escobar M.; Rendon-Velez E.; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)
    Finite element analyses are an important source of information on the biomechanical behaviour of the cervical spine; as well as an important tool in the design and evaluation of spinal instrumentation. This article presents a comprehensive survey of the finite element models of the cervical spine that have been used to study its pathological/nonpathological biomechanics under static/quasi-static loading conditions. Publications that met the inclusion criteria were analysed to extract parameters relative to model identification (e.g., spine segment, population, utility, limitations), model structure (e.g., loading/boundary conditions, anatomical structures, constitutive representation), simulation structure (e.g., software), verification (e.g., convergence) and validation (e.g., validated procedure/output, assumptions). Besides summarizing different modelling approaches with their associated parameters, this article outlines generalities and issues related to the obtainment of such models. The survey shows that authors often fail to report parameters that are critical for the reproducibility of results and that, even with fully reported parameters, these models are inherently difficult to replicate because they generally are patient-specific with their geometry based on data from in-house specimens/subjects. Overall, while the survey contributes to an understanding of the implications of following different modelling approaches and allows to take advantage of previously developed models, further research is required to improve the accuracy and utility of these models. © 2017, Springer-Verlag France SAS, part of Springer Nature.
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    Triaxial deformation behavior of bituminous mixes
    (ASCE-AMER SOC CIVIL ENGINEERS, 2010-02-01) Ossa, E. A.; Deshpande, V. S.; Cebon, D.; Ossa, E. A.; Deshpande, V. S.; Cebon, D.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    The triaxial compressive response of bituminous mixes with volume fractions of aggregate in the range 52 to 85% was investigated over a wide range stresses and strain rates. The types of loadings considered include triaxial monotonic constant stress and constant applied strain rate, as well as creep recovery, continuous cyclic, and stress pulse train loadings. The mixes with a "fully dense" aggregate skeleton were found to dilate under all loading conditions and the creep response of the mixes was dependent on both the deviatoric and hydrostatic stresses. By contrast, recovery was found to occur under zero applied deviatoric stresses with the recovery rate only dependent on the "recoverable strain" and independent of any superimposed hydrostatic stress. Continuous and pulse loading cyclic stress-controlled tests showed that the response of the mixes was governed by the mean applied deviatoric stress in the continuous cyclic tests while strain recovery was important in the pulse loading tests. A phenomenological constitutive model was proposed to fit the measured triaxial response of the bituminous mixes and shown to capture the measurements over all the triaxial stress states and loading time histories investigated here. Furthermore, the model was extended to capture the temperature dependence of the mixtures which is governed by the temperature dependence of the bitumen binder. © 2010 ASCE.