Alessandro Germak

Establishing a world-wide unified Rockwell hardness scale with metrological traceability

Recently developed microform measurement techniques have reduced the measurement uncertainties in the geometry of Rockwell diamond indenters. It is now possible to establish standard-grade Rockwell diamond indenters characterized by high geometric uniformity, high hardness performance uniformity, interchangeability and reproducibility. By using the standard indenters under different national standard machines and a standardized testing cycle, a world-wide unified Rockwell hardness scale could be established with metrological traceability, stability and reproducibility. Geometric measurements and hardness tests in five laboratories have shown that tightly controlled indenter geometry can significantly improve the consistency of Rockwell C hardness (HRC) measurements. These results support the feasibility of establishing a world-wide unified HRC scale with an expanded uncertainty of approximately 0,2 HRC and without significant bias with respect to an ideal scale.

Treatment of Experimental Data with Discordant Observations: Issues in Empirical Identification of Distribution

Treatment of Experimental Data with Discordant Observations: Issues in Empirical Identification of Distribution Performances of several methods currently used for detection of discordant observations are reviewed, considering a set of absolute measurements of gravity acceleration exhibiting some peculiar features. Along with currently used methods, a criterion based upon distribution of extremes is also relied upon to provide references; a modification of a simple, broadly used method is mentioned, improving performances while retaining inherent ease of use. Identification of distributions underlying experimental data may entail a substantial uncertainty component, particularly when sample size is small, and no mechanistic models are available. A pragmatic approach is described, providing estimation to a first approximation of overall uncertainty, covering both estimation of parameters, and identification of distribution shape.

Establishing a worldwide unified Rockwell hardness scale using standard diamond indenters

Recently developed microform measurement techniques have reduced the measurement uncertainties in the geometry of Rockwell diamond indenters. It is now possible to establish standard grade Rockwell diamond indenters characterized by high geometry uniformity, high hardness performance uniformity, interchangeability and reproducibility. By using the standard indenters under different national standard machines and a standardized testing cycle, a worldwide unified Rockwell hardness scale could be established with metrological traceability, stability and reproducibility. Geometrical measurements and hardness tests in five laboratories have shown that tightly controlled indenter geometry can significantly improve the consistency of Rockwell C hardness (HRC) measurements. These results support the feasibility of establishing a worldwide unified HRC scale with an expanded uncertainty (k=2) of approximately ±0.2 HRC and without significant bias with respect to an ideal scale.

Design and metrological evaluation of the new 5 MN hexapod-shaped multicomponent build-up system

The new 5 MN hexapod-shaped multicomponent build-up system (HSM-BUS) represents significant progress in the field of reference transducers in the high force range. As with any build-up system, the presented hexapod-shaped multicomponent force transducer can lead, not only to measure forces 5 times higher than the capacity of a each single uniaxial force transducer (UFT), but gives also information about the other components of the force vector and of the moment vector. Furthermore, the calibration of such types of multicomponent force transducer regards only the calibration of the signal outputs coming from each UFT and the calibration of the geometry of the system. In this work, an a priori evaluation of the expected uncertainty is performed. As a first approximation, the effects of the calibration uncertainties of UFTs and of the geometrical tolerances given on the construction drawing were considered. Subsequently, with a finite element simulation of the mechanical behavior of the 5 MN HSM-BUS under load, a mathematical model of elastic deformations has been evaluated and applied for evaluating and correcting the systematic errors due to the deformation of the geometry under load.