Measurement of elastic modulus by instrumented indentation in the macro-range: Uncertainty evaluation

• This paper refers to indentation modulus measurement in the macro-hardness range.
• A macro-indenting instrument prototype was adopted.
• Experiment was designed to separate the effects of instrument and tested material.
• Uncertainty of measurement methods (ISO 14577) was assessed according to GUM.
• A novel method was proposed to avoid disadvantages of the standardized method.

Elastic modulus is one of the most important parameters evaluated by instrumented indentation test. This paper refers to its measurement in the macro range, where, missing adequate reference materials, traceability proposed by ISO 14577-1 cannot be applied. In this condition, the uncertainty evaluation shall be performed by propagating the uncertainties of the quantities involved in the measurement procedure. This paper describes an experiment, designed in order to separate the possible effects due to the instrument (mainly elasticity effects) and the measured bulk stainless steel test block (mainly non-uniformity of the material). A careful use of design of experiments and other statistical methods allow to clean data from systematic effects and outliers. Thereafter, the application of GUM (Guide to the expression of Uncertainty in Measurement, JCGM 100) allows the expression of uncertainties of the measurement methods proposed by ISO 14577-1 and of a further method here proposed to avoid some disadvantages of the recommended ones.

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