A constitutive model for fcc crystals with application to polycrystalline OFHC copper

Nemat‐Nasser, Sia; Ni, Lei; Okinaka, Tomoo

doi:10.1016/s0167-6636(98)00055-6

Cited by 69 publications

(25 citation statements)

References 19 publications

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“…Data obtained using both cylindrical and SCS specimens have been plotted on the same figure. Additional data points have been inserted, based on the results of Nemat-Nasser et al 9 The current results from the SCS specimen capture the trend and magnitude of the flow stress in the range of strain rates investigated. The characteristic rate sensitivity of OFHC copper is noticeable.…”

Section: A Comparison Between Scs and Cylindersmentioning

confidence: 99%

A shear-compression specimen for large strain testing

Rittel

Lee

Ravichandran

2002

Experimental Mechanics

187

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ABSTRACT--A new specimen geometry, the shearcompression specimen (SCS), has been developed for large strain testing of materials. The specimen consists of a cylinder in which two diametrically opposed slots are machined at 45 ~ with respect to the longitudinal axis, thus forming the test gage section. The specimen was analyzed numerically for two representative material models, and various gage geometries. This study shows that the stress (strain) state in the gage, is three-dimensional rather than simple shear as would be commonly assumed. Yet, the dominant deformation mode in the gage section is shear, and the stresses and strains are rather uniform. Simple relations were developed and assessed to relate the equivalent true stress and equivalent true plastic strain to the applied loads and displacements. The specimen was further validated through experiments carried out on OFHC copper, by comparing results obtained with the SCS to those obtained with compression cylinders. The SCS allows to investigate a large range of strain rates, from the quasi-static regime, through intermediate strain rates (1-100 s-l), up to very high strain rates (2 x 104 s -1 in the present case).

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Section: A Comparison Between Scs and Cylindersmentioning

confidence: 99%

A shear-compression specimen for large strain testing

Rittel

Lee

Ravichandran

2002

Experimental Mechanics

187

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“…In general this tensor is non-symmetric with nine independent values. Therefore, the calculation of the exact GND content for every slip system requires additional assumptions as although there are 12 slip systems for the fcc crystal structure only 6 of them are geometrically independent [247]. Using the material time derivative of Eq.…”

Section: Introduction Of Geometrically Necessary Dislocationsmentioning

confidence: 99%

Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications

et al. 2010

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“…The present study employs the non-work conjugate type theory proposed by Tvergaard (2006, 2008), which is a higher order extension of conventional crystal plasticity theory. Nemat-Nasser et al (1998) suggested a straight forward extension of the widely used visco-plastic power law slip rate relation (Hutchinson, 1976;Peirce et al, 1983), so that the slip rate,γ, on the α'th slip system is given bẏ…”

Section: Introductionmentioning

confidence: 99%

On modeling micro-structural evolution using a higher order strain gradient continuum theory

El-Naaman

Nielsen

Niordson

2016

International Journal of Plasticity

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Published experimental measurements on deformed metal crystals show distinct pattern formation, in which dislocations are arranged in wall and cell structures. The distribution of dislocations is highly non-uniform, which produces discontinuities in the lattice rotations. Modeling the experimentally observed micro-structural behavior, within a framework based on continuous field quantities, poses obvious challenges, since the evolution of dislocation structures is inherently a discrete and discontinuous process. This challenge, in particular, motivates the present study, and the aim is to improve the micro-structural response predicted using strain gradient crystal plasticity within a continuum mechanics framework. One approach to modeling the dislocation structures observed is through a back stress formulation, which can be related directly to the strain gradient energy. The present work offers an investigation of constitutive equations for the back stress based on both considerations of the gradient energy, but also includes results obtained from a purely phenomenological starting point. The influence of model parameters is brought out in a parametric study, and it is demonstrated how a proper treatment of the back stress enables dislocation wall and cell structure * Tel: +45 4525-4020, Fax: +45 4593-1475 URL: saeln@mek.dtu.dk (S.A. El-Naaman)

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A constitutive model for fcc crystals with application to polycrystalline OFHC copper

Cited by 69 publications

References 19 publications

A shear-compression specimen for large strain testing

A shear-compression specimen for large strain testing

Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications

On modeling micro-structural evolution using a higher order strain gradient continuum theory

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