Confirmation of the Measurement Uncertainty Estimation (original) (raw)

Proposal for a practical procedure for the expression of uncertainty in hardness measurements

Hardness measurement is widely used in industrial applications for quality control and acceptance testing of products because it is fast, inexpensive and relatively non-destructive. Uncertainty evaluation is complicated because calibration procedures require the use of direct and indirect verification tests, but the effects on the measurand itself due to test parameters variations are difficult to predict, such as the force-time pattern, inelastic performances of Rockwell indenters and the numerical aperture for Brinell and Vickers indentations measurement. This paper starts by accepting as a matter of fact that standard specifications have demonstrated acceptable performance, indicating that their application is correct for most of the materials generally used. Accepting this premise, the next step was to try to translate the practice, confirmed by many years of experience, into the new language of uncertainty, strongly required by quality documents.

Monte carlo method for evaluation of uncertainty of measurement in brinell hardness scale

Indian Journal of Pure & Applied Physics, 2017

Though method based on law of propagation of uncertainty (LPU), described in GUM, is widely used as an international method for estimation of the uncertainty associated with measurements, JCGM through supplement JCGM 101:2008, which deals with the propagation of distributions, recommends the application of Monte Carlo method (MCM) to evaluate the uncertainty of measurement as an alternative method to LPU. In MCM approach, probability distribution function of measurand has been determined by assigning appropriate probability distribution of the input quantities. In the present paper, effort has been made to discuss the procedure for the application of MCM for computing the uncertainty of measurement of hardness blocks, which have been calibrated by Brinell hardness machine and observations have been recorded. A comparison of the findings of the LPU and MCM has been made, which shows good agreement between the two methodologies adopted. The paper attempts to highlights the MCM for unc...

An Empirical Approach to Determining Rockwell Hardness Measurement Uncertainty

Characteristics of the empirically developed Rockwell hardness test make it difficult to determine measurement uncertainty using methods based on mathematical models describing the relationship between the measurand and the influence quantities. An empirical approach to determining Rockwell hardness uncertainty has been developed, which provides a method based on the familiar procedures and practices of Rockwell hardness testing laboratories. The approach views the hardness machine and indenter as a single measuring device, and considers uncertainties associated with the machine repeatability and the usage of the machine over time with varying environmental conditions and with different operators. The approach also considers the measurement bias of the Rockwell hardness machine as compared to reference standards. An empirical approach for determining Rockwell hardness uncertainty has been developed which provides a method that is based on familiar procedures and practices of Rockwel...

Installation and Uncertainty Evaluation of Reference Hardness Standard of Croatia

Reference hardness standard with HV1 – HV50 measuring range was installed at LIMS (Laboratory for Testing Mechanical Properties) at the end of 2007 with the aim of providing continuous improvement of the metrology infrastructure of Croatia. The evaluation of the measurement uncertainty is one of the most important tasks for establishing this reference standard. Therefore, the influence quantities contributing to the uncertainty were determined and the machine calibrated by direct and indirect method. In this paper the results of the measurements are presented and discussed. A reference hardness machine has been provided to represent the hardness reference standard in Croatia. The machine was made by Indentec, England, type 5030TKV Std. with hardness scale for Vickers. Vickers measurement in the range of force from 9,807 N up to 490,3 N should be realized with uncertainties which assure accurate measurement in the Croatian industry. This reference hardness machine is intended to: -sa...

Application of the software package of engineering analysis for improving the metrological assurance of hardness measurement

Ukrainian Metrological Journal, 2017

Application of the software package of engineering analysis for improving the metrological assurance of hardness measurement The article considers the application of the principle of computational modeling in the construction, improvement and research of the national measurement standards of Ukraine in the field of hardness measurement. The results of modeling research using the finite element method are presented. The methodology of research is proposed in order to improve the characteristics and reduce the uncertainty. The analysis of the further use of computational modeling for the study of components of the national measurement standards is given. The purpose of the article is to improve the research of the measurement standards, particularly, in preparation for international comparisons.

Evaluation of measurement uncertainty – Monte Carlo method

Mechanik

Advantages of Monte Carlo method are presented and compared with A and B type method of measurement uncertainty evaluation. Problem of uncertainty determination, in case of two or more dominant components, is discussed. Results of experiment to evaluate impact of probing strategy on measurement uncertainty of roundness deviation are presented. Issue of ‘systematic error’ in evaluation of coordinate measurement uncertainty is analyzed.

The Quality of Vickers Hardness Tester Calibration

2010

The objective of submitted work is to analyze the influence of the hardness non-uniformity of the used CRM and appraisers doing calibration on its outcome, i.e. conformance or non-conformance of the Vickers hardness tester (HV30) by uncertainty analysis. The results were validated by measurement systems analysis (MSA), unpaired ttest, ANOVA and Z-score. Repeated calibration carried out by two appraisers leads to the identification of tester non-conformance. The statistically significant effect of the CRM non-uniformity and appraisers on the tester nonconformance was proved. According to MSA the studied process is non-capable.

Determination and Uncertainty Propagation of Sensitivity Coefficients in Rockwell Hardness Measurements

SSRN Electronic Journal

In the field of hardness measurements, a problem arises when trying to understand how different measurement parameters (speed of the indenter, force, thermal drift, etc.) affect the outcome of the measurement itself. Because the mathematical model defining hardness scales do not consider such factors, the simplest way to include additional influence parameters in the mathematical model is to introduce them linearly via sensitivity coefficients, which are obtained experimentally and thus characterized by uncertainties. Uncertainties of the sensitivity coefficients are in general not considered in the evaluation of the combined standard uncertainty of the hardness measurements. In this paper a general procedure is presented and applied to HRA and HRC measurements.

The Effect of Indenter Geometrical Errors on the Accuracy and Uncertainty of Vickers Hardness

2011

This paper reports work carried out to determine the influence of the ball indenter geometrical errors on the accuracy of Brinell hardness measurements. Indenters with nominal diameters of 1, 2.5, and 5 mm diameter are tested. Fifteen balls are considered for each nominal diameter. The roundness error of each ball is measured. The diameters of the balls were measured by profile projector and the roundness error was measured by CMM machine. The influence of the ball geometry on the accuracy of hardness is investigated. Six calibrated reference hardness-test blocks are used to perform Brinell hardness test using the 45 selected balls. The results show that the roundness error considerably affects the accuracy of the hardness measurement.

Measurement uncertainty of plane-strain fracture toughness KIC testing by the Monte Carlo Method

REM - International Engineering Journal

The reliable determination of materials' mechanical properties is a fundamental factor for their application in engineering, and the estimation of the measurement uncertainty in testing laboratories has a direct impact on the interpretation of the results. Recent literature demonstrates that one of the most widely used methodologies for uncertainty estimation, the Guide to the Expression of Uncertainty in Measurement (GUM), has limitations, especially in cases where the mathematical model has a high degree of non-linearity. Furthermore, it makes approximations for the final probability distribution. In these cases, it is recommended that the measurement uncertainty is determined by the Monte Carlo Method (MCM), which considers the propagation of the distribution rather than the propagation of uncertainties. Thus, given the limitations of the GUM method and the importance of estimating the measurement uncertainty of mechanical tests, this work aims to implement the measurement uncertainty estimation for the plane-strain fracture toughness (K IC) test of metallic materials through the Monte Carlo Method. The results of the work confirm the importance of estimating the measurement uncertainty of fracture toughness tests.