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U.F. Kocks

Bio: U.F. Kocks is an academic researcher from Los Alamos National Laboratory. The author has contributed to research in topics: Strain hardening exponent & Strain rate. The author has an hindex of 44, co-authored 117 publications receiving 15517 citations. Previous affiliations of U.F. Kocks include Argonne National Laboratory & RWTH Aachen University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a phenomenological model is proposed to incorporate the rate of dynamic recovery into the flow kinetics, which has been successful in matching many experimental data quantitatively, and it has been shown that the proportionality between the flow stress and the square root of the dislocation density holds, to a good approximation, over the entire regime; mild deviations arc primarily attributed to differences between the various experimental techniques used.

2,010 citations

Journal ArticleDOI
TL;DR: In this article, the true stress-strain curves of polycrystalline aluminum, copper, and stainless steel are shown to be adequately represented by an exponential approach to a saturation stress over a significant range.
Abstract: The true stress-strain curves of polycrystalline aluminum, copper, and stainless steel are shown to be adequately represented by an exponential approach to a saturation stress over a significant range. This empirical law, which was first proposed by Voce, is expanded to describe the temperature and strain-rate dependence, and is put on a physical foundation in the framework of dislocation storage and dynamic recovery rates. The formalism can be applied to the steady-state limit of creep in the same range of temperatures and strain rates; the stress exponent of the creep rate must, as a consequence, be strongly temperature dependent, the activation energy weakly stress dependent. Near half the melting temperature, where available work-hardening data and available creep data overlap, they match. Extrapolation of the proposed law to higher temperatures suggests that no new mechanisms may be necessary to describe high-temperature creep. A new differential equation for transient creep also follows from the empirical work-hardening law.

1,357 citations

Journal ArticleDOI
TL;DR: In this article, the axisymmetric deformation behavior of 0.9999 Cu is investigated at strain rates from 10−4 to 104 s−1, and it is shown that the athermal dislocation accumulation rate, or Stage II hardening rate, becomes a strong function of strain rate.

1,145 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a theory for the plastic deformation of metallic glasses below their glass transition temperature is presented based on two modes of thermally activated shear transformations initiated around free volume regions under an applied shear stress.

2,336 citations

Journal ArticleDOI
TL;DR: In this paper, a phenomenological model is proposed to incorporate the rate of dynamic recovery into the flow kinetics, which has been successful in matching many experimental data quantitatively, and it has been shown that the proportionality between the flow stress and the square root of the dislocation density holds, to a good approximation, over the entire regime; mild deviations arc primarily attributed to differences between the various experimental techniques used.

2,010 citations

Journal ArticleDOI
TL;DR: In this paper, a visco-plastic self-consistent (VPSC) anisotropic approach for modeling the plastic deformation of polycrystals, together with a thorough discussion of the assumptions involved and the range of application of such approach is presented.
Abstract: We present in this work a visco-plastic self-consistent (VPSC) anisotropic approach for modeling the plastic deformation of polycrystals, together with a thorough discussion of the assumptions involved and the range of application of such approach. We use the VPSC model for predicting texture development during rolling and axisymmetric deformation of Zirconium alloys, and to calculate the yield locus and the Lankford coefficient of rolled Zircaloy sheet. We compare our results with experimental data and find that they are in good agreement with the available experimental evidence. We also compare the VPSC predictions with the ones of a Full Constraints approach and observe that they differ both quantitatively and qualitatively: according with the predictions of the VPSC scheme, deformation is accommodated mostly by the soft systems, the twinning activity is much lower, and fewer systems are active, in average, per grain. These results are a consequence of having accounted for the grain interaction with its surroundings, which is a crucial aspect when modeling plastically anisotropic materials.

1,834 citations

Journal ArticleDOI
TL;DR: The current understanding of the fundamentals of recrystallization is summarized in this paper, which includes understanding the as-deformed state, nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recystallization, particle effects, and texture.
Abstract: The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

1,797 citations