Seminar by Prof. Jaime MARIAN


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Date | Time
15/12/2017 | 10 h 00 min - 12 h 00 min

Location
IJL Room 2-012

Categories


December 15, 2017, 10:00 AM, IJL, campus ARTEM, room 2-012 (maison signe côté Mines), 2 allée A. Guinier, 54011 Nancy

You are invited to attend Prof. Jaime Marian’s seminar organised by the LabEx DAMAS:

“Predicting the strength of single-crystal tungsten and W (and W-Re alloys) from parameter-free crystal plasticity”

Prof. Marian (http://jmarian.bol.ucla.edu/) will be at IJL on Dec. 13th, 14th and 15th, so please let me know if you would like to schedule discussions with him or feel free to come by my office (ARTEM 03-043) to meet with him on those days.

Abstract:
A distinctive feature of deformation in body-centered cubic (bcc) crystals is the thermally activated motion of screw dislocations at low homologous temperatures, which manifests itself as a pronounced temperature dependence of the yield and flow stresses.  As well, bcc metals are known to display a tension/compression asymmetry derived from the existence of non-Schmid resolved stresses. Bcc plasticity cannot be understood without consideration of these two phenomena, which originate in the atomic structure of dislocation cores and thus have to be studied at the appropriate scales. At the same time, the plastic behavior of metallic single-crystals is highly dependent on orientation and strain rate. However, these are macroscopic-level dependencies that cannot currently be studied with atomistic methods directly. This means that a connection must be made between calculations at the dislocation core level and at the material point level, spanning many orders of magnitude in time and space. In this work, we assemble a computational methodology grounded on an atomistic description of screw dislocation properties and non-Schmid effects, implemented into a crystal plasticity model of bcc metal deformation. We find that the complete methodology is successful in predicting the experimentally measured temperature dependence of the flow stress in tungsten for several crystallographic orientations, without the need for any fitting to experimental data whatsoever. We show results for the strength of W as a function of temperature, loading orientation, strain rate, and tension/compression, and identify conditions under which the modeling could be used to map out a high-dimensional parametric space.