Abstract
In this paper, the experimental procedure and calculation model for the measurement of the indentation modulus by using the primary hardness standard machine at INRiM in the macro-scale range at room temperature is described. The indentation modulus is calculated based on the Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness, and hardness indentation imaging. Measurements are performed with both pyramidal (Vickers test) and spherical indenters (Brinell test). Test force is provided by a dead-weight machine, and the occurring displacement is measured by a laser-interferometric system. The geometrical dimensions of both the Vickers and Brinell indentations are measured by means of a micro-mechanical system and optical microscopy imaging techniques. Applied force and indentation depth are measured simultaneously, at a 16 Hz sampling rate, and the resultant loading-unloading indentation curve is obtained. Preliminary tests are performed on metal and alloy samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed.
Highlights
The elastic properties of materials in mechanical engineering and material science can be evaluated by means of several different experimental techniques that are based on static, quasi-static, and dynamic methods
The indentation modulus is calculated based on the Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness, and hardness indentation imaging
This paper has described a method for the evaluation of the indentation modulus by using the primary hardness standard machine at INRiM in the macro-scale range, with both Vickers and Brinell indenters
Summary
The elastic properties of materials in mechanical engineering and material science can be evaluated by means of several different experimental techniques that are based on static, quasi-static, and dynamic methods. Techniques involving instrumented indentation (from the nano to the macro scale) that are used to evaluate the elastic properties of materials and procedures are embodied in ISO 14577-1 [1] (for metallic materials). The first attempts to measure hardness and elastic modulus by instrumented indentation were made in 1983 by Pethicai, Hutchings, and Oliver, investigating a method of evaluating hardness at a nano-scale level. Their findings showed that depth-sensing indentation allows the construction of a loaddisplacement curve, which is strongly related to the typical stress-strain diagrams of materials [3]. Measurements are performed using the primary hardness dead weight machine, designed and realized at INRiM
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