Examinando por Materia "Constitutive models"

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    Dislocation density based flow stress model applied to the PFEM simulation of orthogonal cutting processes of Ti-6Al-4V
    (MDPI AG, 2020-01-01) Rodríguez, J.M.; Larsson, S.; Carbonell, J.M.; Jonsén, P.; Rodríguez, J.M.; Larsson, S.; Carbonell, J.M.; Jonsén, P.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Mecatrónica y Diseño de Máquinas
    Machining of metals is an essential operation in the manufacturing industry. Chip formation in metal cutting is associated with large plastic strains, large deformations, high strain rates and high temperatures, mainly located in the primary and in the secondary shear zones. During the last decades, there has been significant progress in numerical methods and constitutive modeling for machining operations. In this work, the Particle Finite Element Method (PFEM) together with a dislocation density (DD) constitutive model are introduced to simulate the machining of Ti-6Al-4V. The work includes a study of two constitutive models for the titanium material, the physically based plasticity DD model and the phenomenology based Johnson-Cook model. Both constitutive models were implemented into an in-house PFEM software and setup to simulate deformation behaviour of titanium Ti6Al4V during an orthogonal cutting process. Validation show that numerical and experimental results are in agreement for different cutting speeds and feeds. The dislocation density model, although it needs more thorough calibration, shows an excellent match with the results. This paper shows that the combination of PFEM together with a dislocation density constitutive model is an excellent candidate for future numerical simulations of mechanical cutting. © 2020 by the authors.
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    Spherical indentation behavior of asphalt mixtures
    (ASCE-AMER SOC CIVIL ENGINEERS, 2007-01-01) Ossa, E.A.; Collop, A.C.; Ossa, E.A.; Collop, A.C.; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de Ingeniería
    The spherical indentation response of a dense bitumen macadam asphalt mixture with two different volume fractions of bitumen binder is investigated both experimentally and via an analytical model. The model for the indentation of bitumen developed by Ossa et al. in 2005, was used to study the spherical indentation behavior of the mixtures with good agreement when compared to experimental results. An extensive experimental study of the monotonic and recovery spherical indentation behavior is reported for a range of temperatures. In line with the predictions of the model, the monotonic indentation response of the mixtures exhibits a power-law dependence on the indentation force. The model is also successful in capturing the indentation recovery behavior of the mixtures. A comparison of the material parameters obtained from uniaxial compression and indentation tests showed that indentation tests can be used in an easy and reliable way to obtain the fundamental asphalt parameters. Further, parameters found from indentation tests implicitly account for the confining conditions generated by the aggregate particles below the indenter. © 2007 ASCE.