Evaluation of the error of indirect measurements of physical-mechanical characteristics of materials by dynamic indentation method

The metrological problems of measuring the physic and mechanical characteristics of materials by dynamic indentation are considered. It is shown that the estimation of measurement error demanding the creation of the reference blocks is ineffective due to the wide variety of controlled materials and a wide range of changes in their properties. A technique has been developed for evaluating the accuracy of measurements based on the errors of individual parameters included in the calculation equation, i.e. by determining the error of indirect measurements. The technique is based on the estimation of the boundaries of the random error of the measured characteristics of the material and the non-excluded systematic errors of the parameters that are used for the calculations of needed characteristics. The results of experimental studies are presented, indicating that due to the different character of the dependencies of hardness and elastic modulus, the error in measuring the elastic modulus exceeds the error in measuring hardness. In addition, it was found that the error in measuring the characteristics of materials by the dynamic indentation method exceeds the measurement error by the static indentation method and can be reduced by increasing the accuracy of the equipment used for the registration of impact process. The obtained values of the physic and mechanical characteristics of the materials and the values of the measurement error show that the dynamic indentation method can effectively solve the problem of non-destructive testing of hardness, elastic modulus, and strain hardening exponent of metals and products with an appropriate error.

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