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Lecture

A Simple Method for the Extraction of Steady-State Creep Parameters from Indentation Data via Finite Element Modelling

Tuesday (27.09.2016)
17:00 - 17:15
Part of:


Analytical methods for extracting steady-state creep parameters from indentation data are inherently unreliable [1,2]. They cannot adequately capture the evolution of complex stress and strain fields and they neglect in all cases the contributions to deformation from primary creep (which cannot be avoided during indentation). More reliable procedures for extracting steady-state creep parameters must necessarily involve some form of finite element modelling, and one such method is presented here. It involves the adjustment of input parameters in a constitutive creep equation inside an indentation finite element model. The model is then repeatedly run, generating for each set of input parameters a displacement-time history during a constant-load-hold indentation test. Each of these histories is systematically-compared to a measured displacement-time history, obtained from tests on Zinc. The level of agreement between the measured and predicted data is quantified using a “goodness-of-fit” parameter. It is then shown that, in order to converge on a “unique” combination of input parameters it is necessary to repeat this operation using a different indenter shape.


[1] Dean, J., et al. "A critical assessment of the “stable indenter velocity” method for obtaining the creep stress exponent from indentation data." Acta Materialia 80 (2014): 56-66.

[2] Dean, J., et al. "A procedure for extracting primary and secondary creep parameters from nanoindentation data." Mechanics of Materials 65 (2013): 124-134.

 

Speaker:
James Campbell
University of Cambridge
Additional Authors:
  • Dr. James Dean
    University of Cambridge
  • Prof. Bill Clyne
    University of Cambridge