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Some critical discussion of the state of the art of uncertainty evaluationin Instrumented Indentation Testing IIT
Nowadays the Instrumented Indentation Testing (IIT), in the nano range often named as nano indention, is one of the most commonly used methods to determine the mechanical properties of materials in the micro and nano range. This method is already extensive standardized in ISO 14577 part 1-4. In the past, the application of this standard in testing praxis shows that the established values have an excellent precision.If an uncertainty is calculated, the range of values within which the true value is asserted to lie with some level of confidencewill be known. In part 1 of ISO 14577 [1] two methods for evaluation of the uncertainty in IIT are mentioned:
Method 1 for determining uncertainty considers only those uncertainties associated with the overall measurement performance of the testing machine with respect to the reference blocks.
Method 2calculates a combined uncertainty from individual contributions. These may be grouped into random and systematic uncertainties.
Both methods will be described in detail using examples from the dailyexperimental praxis. The comparabilityof both methods will be critically discussed. Finally, it will be showedhow the calculated uncertaintiescan be used for performancetests and product specifications.
Acknowledgement
This work was performed under the support of the EMPIR project 17NRM05Advancing measurement uncertainty̶ comprehensiveexamples for key international standards
References
[1] ISO 14577 part 1 (2017)
Nowadays the Instrumented Indentation Testing (IIT), in the nano range often named as nano indention, is one of the most commonly used methods to determine the mechanical properties of materials in the micro and nano range. This method is already extensive standardized in DIN EN ISO 14577 part 1-4. In the past, the application of this standard in testing praxis shows that the established values have an excellent precision. On the other side, the trueness as comparability of obtained results with reference values is not so good. To improve accuracy of IIT the use of a variable ε and the consideration of the lateral displacement during indentation became normative requirements during the last revision of ISO 14577.
Starting with the beginning of instrumented indentation testing in 1898 the historical background and the main assumption of the Oliver and Pharr method will be explained and critical discussed. It will be shown how to apply the use of a variable ε and the consideration of the lateral displacement during indentation in the daily testing work to improve accuracy of IIT.
Finally, ongoing standardization projects in the field of IIT will be briefly presented.
The paper addresses the “Functional coatings for mechanical applications: characterization and standardization” and the following points are discussed in more detail:
1. Mechanic alapplications (coatings for tools and components, system features vs. material parameters)
2. Mechanical characterization (instrumented indentation testing (IIT), centrifugal adhesion testing (CAT), state of standardization)
3. Topometric characterization (white light interference microscopy (WLIM, 3D), mechanical stylus (MS, 2D), state of standardization)
4. Optical characterization (spectroscopic ellipsometry (SE), inter-laboratory comparison, state of standardization)