World-wide Unified Scales for the Rockwell Hardness Test with Conical Indenters (original) (raw)
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Influence of the indenter shape in Rockwell hardness test
Proc. of the HARDMEKO '98, …
One of the main problems related to Rockwell hardness measurements is the influence of the indenter shape. In the present work the effects of the macro-geometry of the diamond indenter are analyzed as influencing parameters in Rockwell C test. Both an experimental analysis is carried out, using IMGC National Standard Machine, and a finite element simulation (FEM) is performed. Four different theoretical models are proposed to interpret experimental results: the first model is based on Brinell definition of hardness, the second on Meyer analysis and the last two are based on the evaluation of the deformation work through the analysis of the indentation volume. These different corrections are compared to evaluate their performances.
Developing definitions of conventional hardness tests for use by National Metrology Institutes
Measurement: Sensors, 2021
This paper describes the process used by the Consultative Committee for Mass and Related Quantities-Working Group on Hardness (CCM-WGH) of the International Committee of Weights and Measures (CIPM) to develop international definitions of the conventional Rockwell, Brinell, Vickers and Knoop hardness test methods, for use by the National Metrology Institutes (NMI) that standardize hardness measurement.
Geometric Measurement Comparisons for Rockwell Diamond Indenters
In the uncertainty budget of Rockwell C hardness (HRC) tests, geometric error of the Rockwell diamond indenter is a major contributor. The geometric calibration of Rockwell diamond indenters has been a key issue for Rockwell hardness standardization. The National Institute of Standards and Technology (NIST) developed a microform calibration system based on a stylus instrument for the geometric calibration of Rockwell diamond indenters. Using that system, a NIST master standard Rockwell diamond indenter No. 3581 was established in 1995, by which approximately 300 standard reference material (SRM) Rockwell hardness blocks of HRC scale were calibrated for implementation of the HRC scale in the United States. This indenter has been re-calibrated in 1997, 2005 and 2007. The calibration results have shown both high stability for the NIST standard Rockwell diamond indenter and high reproducibility for the NIST microform calibration system. After more than fifteen years of service, the styl...
CALIBRATION REPRODUCIBILITY TEST FOR NIST's No. 3581 STANDARD ROCKWELL DIAMOND INDENTER
Standard Rockwell diamond indenters play an important role for a worldwide unified Rockwell hardness scale. In 1994, the National Institute of Standards and Technology (NIST) established a Microform Calibration System with sufficiently small calibration uncertainty for the calibration of standard Rockwell indenters. In 1995, NIST established a group of Rockwell diamond indenters characterized both by high geometrical uniformity and hardness performance uniformity. One of them, No. 3581, was selected as the NIST's primary Rockwell diamond indenter for the calibration of NIST's Standard Reference Material (SRM) Rockwell C hardness blocks. This indenter was recalibrated in 1997 and 2005. The calibration results showed high stability for the microform geometry of the NIST's standard Rockwell diamond indenter, as well as high calibration reproducibility for the NIST's Microform Calibration System.
Effect of Steel and Tungsten Carbide Ball Indenters on Rockwell Hardness Tests
Rockwell hardness (HR) is a valuable and widely used indentation hardness test for evaluating mechanical properties of metallic materials. For the Rockwell scales that use a ball indenter, either a steel or tungsten carbide (WC) ball indenter is permitted to be used in the test method standards of ASTM International and International Organization for Standardization (ISO). However, significant differences occur in Rockwell hardness tests depending on whether a steel or WC ball is used. In this paper, finite element analysis (FEA) is used to simulate the HR indentation process. The effects of four different sizes of steel and WC ball indenters on different Rockwell hardness scales are studied and compared with experimental measurements. This study provides important approximations of the differences between the performance of steel and WC Rockwell hardness indenters.
Metrologia, 2020
This report describes a bilateral EURAMET supplementary comparison on Rockwell hardness scales of two national metrology institutes of Italy and Turkey, INRiM and UME, respectively. The pilot laboratory is INRiM in the comparison where three sets of hardness reference blocks for the Rockwell hardness scales of HRA, HRBW and HRC were used. Each set of blocks consists of four hardness reference blocks for HRA and HRBW and five blocks for HRC hardness scales. The comparison was realized as planned in the Technical Protocol with some delay. The measurement results and uncertainty assessments declared by INRiM and UME are in consistency with each other. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Metrological Characterization of Hardness Indenter Calibration System
Journal of Physics: Conference Series
There are four main components constituting the conventional hardness scales, in all types of hardness measurements, from testing machines to standardizing ones : Force application, indentation size measurement, indenter and measurement cycle. To assure the quality, reliability and uniformity in hardness measurement in all over the world it is important to constitute traceability of each parameter to the base SI units and confirm the performance of the system as a whole. One of the most interesting subject to be discussed is the calibration of the geometrical properties of the diamond indenters used in Rockwell and Vickers scales, sphero-conical Rockwell and square-based pyramid Vickers diamond indenters. The indenters to be used in testing and calibration/standardizing machines are supposed to be in accordance with some international hardness standards , namely ISO 6507-2 [5] and ISO 6508-2 [2] for testing Vickers and Rockwell mach ines, respectively; ISO 6507-3 [6] and ISO 6508-3 [3] for Vickers and Rockwell calibration/standardizing machines, respectively, and relevant ASTM standards. This paper describes the metrological characterization of UM E Hardness Diamond Indenters Calibration System and the traceability of each measured parameter subject to calibrat ion.
Performance tests for qualifying metrological Rockwell indenters
Much work has been done on Rockwell diamond indenters to evaluate the relationship between geometry and hardness measurement results. However, it has been observed that the residual after geometrical correction is significant (within ±0,3 HRC). Some investigations on the non-geometric parameters of the Rockwell diamond indenters, as mechanical properties of the diamonds and the soldering of the diamond prism into the holder, were carried out in the past. Recently, using the INRiM primary machine, some experimental tests were carried out to investigate the possibility to correlate the differences on hardness measurements observed using different indenters to the nongeometric characteristics of indenters. The results show that this correlation exists and it can justify the discrepancies.
Experimental analysis on the influence quantities in the Rockwell C hardness test
Hardness is a conventional quantity defined by means operational rules in procedures described in the relevant standards. As it is well known, this method gives some problems on the side of uncertainty evaluation. The intrinsic limit is the difficulty to evaluate the sensitivity coefficients of all the influence parameters involved in the measurement procedure. This subject was recently faced in the framework of the European cooperation for Accreditation of Laboratories. IMGC has carried out an experimental analysis, limited to Rockwell C scale, within which a quasi-factorial experimental plan has been used to evaluate the influence of time and velocity of all indentation phases. The results of this analysis could be useful as support for the evaluation of uncertainty, made following the recent International and European guides.
The influence of geometrical tolerances of Vickers indenter on the accuracy of measured hardness
2012
This paper reports work carried out to determine the influence of the Pyramidal indenter geometrical errors and tolerances on the accuracy of Vickers hardness measurements. The angle between the opposite faces and line of conjunction of nine indenters were measured by the optical comparator. The influence of the indenter geometry on the hardness accuracy is investigated. Three calibrated reference hardness test blocks were used to check the Vickers hardness test using the nine selected indenters. The results show that the geometrical error of the indenters (specially the angles) considerably affects the accuracy of the hardness measurement. Finite element analysis of the indentation process into metallic test pieces was conducted. Comparison of the experimental results with the numerical findings was discussed. Errors in the experimental values are correlated with measured tolerances in the angles between faces.