Abstract
Load and hold conical indentation responses calculated for materials having creep stress exponents of 1.15, 3.59 and 6.60 are regarded as input ‘experimental’ responses. A Bayesian-type statistical approach (Zhang et al. 2019 J. Appl. Mech. 86, 011002 (doi:10.1115/1.4041352)) is used to infer power-law creep parameters, the creep exponent and the associated pre-exponential factor, from noise-free as well as noise-contaminated indentation data. A database for the Bayesian-type analysis is created using finite-element calculations for a coarse set of parameter values with interpolation used to create the refined database used for parameter identification. Uniaxial creep and stress relaxation responses using the identified creep parameters provide a very good approximation to those of the ‘experimental’ materials with stress exponents of 1.15 and 3.59. The sensitivity to noise increases with increasing stress exponent. The uniaxial creep response is more sensitive to the accuracy of the predictions than the uniaxial stress relaxation response. Good agreement with the indentation response does not guarantee good agreement with the uniaxial response. If the noise level is sufficiently small, the model of Bower et al. (1993 Proc. R. Soc. Lond. A 441, 97–124 ()) provides a good fit to the ‘experimental’ data for all values of creep stress exponent considered, while the model of Ginder et al. (2018 J. Mech. Phys. Solids 112, 552–562 ()) provides a good fit for a creep stress exponent of 1.15.
Highlights
The serviceability and reliability of a variety of engineering components, as for example, in turbines used for electricity generation and in vehicle and aeroplane engines, are limited by continuing deformation at relatively low stress levels, i.e. creep
The differences between indentation depths when t0 > 10−4 were less than 2.7%, 0.2% and 0.1% for Se, CsHSO4 and Sn, respectively
Finite-element calculations were carried out to populate a coarse database of power-law creep parameters
Summary
The serviceability and reliability of a variety of engineering components, as for example, in turbines used for electricity generation and in vehicle and aeroplane engines, are limited by continuing deformation at relatively low stress levels, i.e. creep. In [2,10,11,12] experimental creep indentation data were related to uniaxial power-law creep properties using analytical results from Bower et al [1] and from the expanding cavity model of Ginder et al [2]. The Bayesian statistics-based approach of Zhang et al [15] is used to extract powerlaw creep parameters from the indentation depth versus time response and the residual surface profile. The power-law creep parameters identified via indentation, using noise-free as well as noise-contaminated data, are compared with the corresponding uniaxial creep and stress relaxation responses of the input ‘experimental’ materials. (iv) How do the power-law creep properties obtained using the analytical steady-state creep results of Bower et al [1] and Ginder et al [2] compare with those predicted from the Bayesian-type statistical approach?
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