Abstract

The nanoindentation (NI) experiment is an effective method to evaluate the micromechanical property of materials. The substrate effect is a nonnegligible factor which could influence the accuracy of the NI experiment result. Large numbers of previous studies have focused on the substrate effect based on the coating/substrate model, whereas the substrate effect in the testing of the hybrid material was rarely involved. The real NI experiment and the numerical simulation method were adopted to reveal the characteristics of the substrate effect in the NI experiment of the hybrid material in this paper, such as the rock or cement material. The peak displacement h peak and the residual displacement h residual of the indenter, which could obtain directly from the NI experiment and were usually considered as key basic variables to calculated other parameters, were selected as evaluation indexes of the substrate effect. The results indicated that there was a significant difference of the NI experiment result between the coating/substrate and the hybrid material under the same condition. The lateral boundary stiffness and discontinuous face were considered as main factors that induced this difference, and their effect were analysed, respectively. Young’s modulus E s and Poisson’s ratio μ s of the substrate were selected as the variables in the parametric study, and the relationship between them and the NI experiment result were discussed.

Highlights

  • Academic Editor: Gaofeng Song e nanoindentation (NI) experiment is an effective method to evaluate the micromechanical property of materials. e substrate effect is a nonnegligible factor which could influence the accuracy of the NI experiment result

  • In the comparative group of c1 versus a1, hpeak and hresidual obtained by the hybrid material model are both bigger than the results obtained by the coating/ substrate combination model, whereas the conclusion is reverse in other comparative groups

  • A NI experiment was introduced firstly; this experiment shows the substrate effect in the hybrid material. en the series of numerical experiments were carried out to explore the substrate effect in the nanoindentation experiment of the hybrid material. e results shows that the numerical experiments present are consistent with experiments. e following are mainly conclusions obtained in this paper

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Summary

Experiment

To reveal the substrate effect in the hybrid material, a series of experiments were conducted with the NI technology. e hybrid material was selected as the hardening cement, and the tested object was selected as the unhydrated cement granular, which was unavoidable and existed in the hardening cement. E results show the peak indenter displacement in tests ranges from 71 to 94 nm in substrate of cement and more than 500 nm in substrate of epoxy resin. A vertical load of 500μN was gradually applied on the rigid reference point of indenter During this process, the testing material (or the coating) deformation transferred from elastic to plastic, and the substrate significantly deformed correspondingly. The load which was applied on the rigid reference point was designed to decrease to zero In this process, the elastic deformation of the system gradually recovered, whereas the plastic deformation was retained

Results and Discussion
H24 H25 H26
Conclusion

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