ELFT HÍRADÓ

[Gubicza Jeno <gubicza AT ludens.elte.hu>]

                                MEGHIVO

                az ELTE TTK Altalanos Fizika Tanszek
                            szeminariumara

                          Professor J.L.Martin
(Departement de Physique, Ecole Polytechnique Federale de Lausanne,
Switzerland)

Characterizing thermally activated deformation mechanisms of crystals
                                
Abstract

In a famous paper, in 1940, Orowan proposed a simple rule, named the "
Orowan equation " : it says that the plastic strain-rate of a deforming
crystal is proportional to the mobile dislocation density times their
velocity (average quantities and steady state conditions). Fifty years after
his statement,it is not possible to determine (or to predict) how a
deforming crystal adjusts its mobile dislocation density and velocity for a
given strain-rate.
It will be shown how transient mechanical tests are able to bring some
answer to this question. These consist of load relaxation experiments and
creep tests performed along a monotonic deformation curve. The experimental
procedures of single (as well as repeated) transient tests will be
described, together with the assumptions and equations necessary for their
interpretation. Some results will be presented for different classes of
crystals, such as a FCC metal, an ordered intermetallic compound and a
covalent crystal. Examples of informations extracted from these tests will
be given, such as activation energies (and areas) related to the dislocation
velocity, as well as structural changes which take place during plastic
deformation.


Helye: ELTE TTK Eszaki Tomb, Altalanos Fizika Tanszek
        1117 Budapest, Pazmany Peter setany 1/A, 4.emelet 4.52.terem

Ideje: 2001. aprilis 17. kedd, 9.00. (a szokasos 8.30. helyett!!!)

Minden erdeklodot szivesen latunk.

Az 2000/2001 II. felevi program megtalalhato a kovetkezo cimen:
http://metal.elte.hu

                                        
                                                        Gubicza Jeno