Indentation creep vs. indentation relaxation: A matter of strain rate definition?

Paul Baral (1, 2, 3, 4) , Guillaume Kermouche (3, 4) , Gaylord Guillonneau (1, 2) , Gabrielle Tiphéne (1, 2) , Jean-Michel Bergheau (1, 5) , Warren C. Oliver (6) , Jean-Luc Loubet (1, 2)

1 LTDS - Laboratoire de Tribologie et Dynamique des Systèmes
2 ECL - École Centrale de Lyon
3 LGF-ENSMSE - Laboratoire Georges Friedel
4 SMS-ENSMSE - Centre Science des Matériaux et des Structures
5 ENISE - Ecole Nationale d'Ingénieurs de Saint Etienne
6 KLA Nanomechanics Inc., Oak Ridge, TN 37830, USA

An extensive study of the different methods able to measure material creep properties in indentation is proposed. A systematic comparison of the fast creep, long-term creep, constant strain rate and long-term relaxation tests is performed on amorphous selenium. Even though measured apparent activation energy and strain rate sensitivities are very similar for all tests, a discrepancy is highlighted between the creep/constant strain rate tests and the relaxation tests. This effect seems to be related to the strain rate definition which should be a function of the strain rate sensitivity m. In this paper, it is proposed to use a representative strain rate ϵ̇r as proposed by Kermouche et al. (2008). An excellent agreement is found between all the methods, including uniaxial compression when expressing the creep behavior as a function of representative stress and strain rate.

Mots clés: Nanoindentation; Strain rate sensitivity; Relaxation; Creep; Selenium

Domaines: Matériaux

Paul Baral, Guillaume Kermouche, Gaylord Guillonneau, Gabrielle Tiphéne, Jean-Michel Bergheau, et al.. Indentation creep vs. indentation relaxation: A matter of strain rate definition?. Materials Science and Engineering: A, 2020, 781, pp.139246. ⟨10.1016/j.msea.2020.139246⟩. ⟨emse-04511474⟩