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Vytautas Vasauskas, Vytautas Capas
PARTICULAR ASPECTS IN THE CALIBRATION AND APPLICATION DYNAMIC AND STATIC HARDNESS

The paper summarizes some results obtained at investigation of the main quantities influencing the uncertainty of measuring dynamic hardness. Some parameters concerning the force and time behaviour for full test cycle (loading and unloading) is discussed in terms of a systematic characterization of the dynamic set up used. The technique parallels the method for static indentation hardness determination and allows direct comparisons between dynamic and static hardness measurements.

L. Ma, S. Low, J. Song, J. Zhou
DETERMINING MECHANICAL PROPERTIES OF O1 TOOL STEEL FROM REVERSE COMPUTATION OF INDENTATION MEASUREMENT

Besides obtaining the hardness of materials, the indentation test has also been developed as a popular method for investigating mechanical properties. There exist some empirical or semi-analytical methods for determining the hardness, Young’s modulus and work hardening exponent from indentation experiments. In this paper, a reverse computation method is introduced to determine the elastic modulus and stress-strain curve of O1 tool steel from the Rockwell C hardness (HRC) indentation test combined with finite element analysis (FEA) simulation. The forcedepth data from the HRC spheroconical indentation measurement is used to start an iterative FEA simulation procedure to extract the elastic-plastic stress-strain relationship which is consistent with the experimentally measured data. The reverse computation results agree well with HRC test results.

Sheau-shi Pan, Chiu-Hsien Chen, Chi-Sheng Chang
EVALUATION OF THE UNCERTAINTY DUE TO ABBE’S ERROR FOR PRIMARY ROCKWELL HARDNESS STANDARD SYSTEM

The Primary Rockwell Hardness Standard System was established in the Center for Measurement Standards since July 1996 till June 1997. During the time, a laser interferometer, HP10737R 3-axis compact interferometer system, was substituted for the optical linear scale and combined with the mechanical structure of the original system to measure the Rockwell Hardness nominated values from 20 HRC to 70 HRC. Subsequently the laser interferometer was performed the measurement of the pitch and yaw of the indenter when the hardness was measured; then we evaluated the uncertainty caused by the Abbe’s error, pitch and yaw. The results showed that the expanded uncertainty of the primary Rockwell hardness standard system due to the Abbe’s error of the indenter was 0,046 HRC at the confidence level of 95%. The expanded uncertainty caused by the angle difference between the indenter moving axis and the measuring optical path was 0,0028 HRC at the confidence level of 95%.

Renato R. Machado, Tácito B. Pinto, Itamar Ferreira
COMPARISON BETWEEN CONVENTIONAL ROCKWELL HARDNESS TESTING AND INSTRUMENTED INDENTATION TESTING

With base in the precepts and technical procedures of ISO 6508-1 standard and ISO/FDIS 14577-1 standard draft, Rockwell hardness testing and instrumented indentation testing (IIT) were carried out using a universal testing machine, through adaptation of a system developed for these ends. The results pointed out a good relation between the two hardness tests, taking into account that IIT can provide other materials parameters besides being the simplest method, not requiring any preliminary force or operator influence. Nevertheless, it was observed the necessity of the improvement of the used system, regarding the monitoring of zero-point.

Vilson Berilli Mendes, Fabiana R. Leta
AUTOMATIC MEASUREMENT OF BRINELL AND VICKERS HARDNESS USING COMPUTER VISION TECHNIQUES

In this paper we present a methodology to automatic measure the hardness indentation, by using Computer Vision techniques. The main focus is the indentation measurement. With this methodology the user’s skill has no influence in the final hardness result.

Giulio Barbato, Alessandro Germak, Samuel Low
PROPOSAL FOR A PRACTICAL PROCEDURE FOR THE EXPRESSION OF UNCERTAINTY IN HARDNESS MEASUREMENT

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.

Robert A. Ellis
UNCERTAINTIES OF VICKERS HARDNESS TEST BLOCKS

Uncertainties of Vickers hardness can be calculated for every individual Vickers hardness test block using the standardizing testing machine uncertainty components and the non- uniformity of the reference material. Unlike the Rockwell test for example, the test components can be directly related to the outcome of the uncertainty of the Vickers test. It can be shown in some cases that the reference uncertainty is larger than the accepted tolerances at the lower end of the hardness ranges.

Giulio Barbato, Alessandro Germak, Konrad Herrmann, Samuel Low
EVOLUTIONS IN HARDNESS SCALES DEFINITION

A conventional characteristic of hardness measurements is the strong dependency on the official definition of each scale. For this reason, and to assure a good connection between National Metrology Institutes (NMIs), scientific organizations (e.g., IMEKO1) and international organizations for standardization (e.g., ISO2 and OIML3), a new Working Group on Hardness (WGH) was created a few years ago under the Consultative Committee for Mass and Related Quantities (CCM) of the Comité International des Poids et Mesures (CIPM). One of the principal aims of the WGH is to analyze the level of accuracy corresponding to the state-of-the-art of national primary standards, ultimately leading to improvements in the hardness scale definitions and, at the same time, providing well-defined traceability, in terms of uncertainty, of industrial measurements. Recent efforts to improve hardness scale definitions and the consequential reduction of uncertainty are presented in this paper. Contributing to this effort are the NMIs that currently maintain hardness standards and those that have plans to realize them in the near future. By improving the definitions and the associated uncertainty, certain advantages will be obtained at all levels in the dissemination of hardness standards: from the calibration and testing laboratories to industrial measurement applications.

Konrad Herrmann, Anton Stibler, Imre Patkovszky, Peter Strobel, Febo Menelao
INVESTIGATION OF A CALIBRATION DEVICE FOR THE DEPTH MEASURING SYSTEM IN ROCKWELL HARDNESS TESTING MACHINES

The paper describes investigations on the metrological properties of a newly developed calibration device for the depth measuring system in Rockwell hardness testing machines. The special feature of this calibration device is the inductive measuring system and that it is used under acting test force. The investigation of the calibration device is carried out with two different reference devices. As main result of the investigation an uncertainty of measurement U ˜ 0,24 µm of the calibration device was proven.

Giulio Barbato, Gabriele Brondino, Maurizio Galetto
FORCE CALIBRATION OF INSTRUMENTED HARDNESS TESTERS

In this paper a methodology for calibration of force transducers used for hardness testers is described. The methodology associates to the standard procedure a method to evaluate and correct other effects such as promptness, creep and hysteresis. After a general description, a practical application is reported.

Page 914 of 936 Results 9131 - 9140 of 9356