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Th. Choudoba, M. Griepentrog, U. Beck
COMPARISON BETWEEN VICKERS HARDNESS AND INDENTATION HARDNESS

The Vickers hardness is an often used hardness definition, mainly in the force range above 0.5 N. With decreasing film thickness and the need of lower loads, depth and force sensing measurement techniques became more and more important and a new indentation hardness was introduced, finally resulting in the international standard ISO 14577. Therefore investigations regarding the comparability of both hardness definitions are of high interest. In principle it should be possible to obtain the same hardness number with both measurement methods if the true contact area can be determined. The agreement is checked for a large selection of materials and instruments for a force of 0.5 N (HV0.051). The calculation of the correct contact area from depth sensing measurements is also checked by a comparison of the indentation modulus with the Young’s modulus, obtained with other methods.

Ch. Ullner, Th. Reich
STUDY ON THE CAPABILITY OF MATERIALS AS REFERENCE BLOCKS FOR THE MACRO RANGE OF INSTRUMENTED INDENTATION TEST

Part 3 of the ISO 14577 “Instrumented indentation test for hardness and materials parameters“ (IIT) concerns the calibration of reference blocks. Besides the widely spread activities for supplying reference blocks in the nano and micro range it is needed to be taken into account the macro range too. The paper reports on test results on ceramic materials which are tailored for reference blocks. The specimens made of Si3N4, SiC, or Al2O3 ceramics are highly homogenous and exhibit an increased quality with a roughness Ra ≤ 0.005 µm. They are successfully used for reference blocks of the traditional Vickers and Knoop hardness. In comparison, the capability of hardened steel which is used for traditional hardness techniques is studied.

M. Griepentrog, Ch. Ullner, A. Dueck (A. Dück)
INSTRUMENTED INDENTATION TEST FOR HARDNESS AND MATERIALS PARAMETER FROM MILLINEWTONS TO KILONEWTONS

The ISO/DIS 14577 Metallic materials - Instrumented indentation test for hardness and materials parameters – Part 1-3 (IIT) concerns test forces up to 30 kN. The paper reports on IIT at test forces ranging from 0.002 N to 1000 N on non – magnetizable steel X8 CrMnN 18- 18 (1.386) with well polished surface using Vickers indenter and four hardness machines of different design (Nano Indenter XP, Fischerscope H 100, Zwick Z005 with Universal hardness head and a laboratory four-column set up materials testing machine) according to the standard. Using mostly identical test parameters the results of the different machines are almost in good agreement. Estimated small differences are caused by the different uncertainties of the used machines and by different methods of mathematical analysis of the detected raw data.

F. Loeffler (F. Löffler), A. Sawla, P. Strobel
CALIBRATION OF THE DEPTH-MEASURING DEVICE OF ROCKWELL HARDNESS TESTING MACHINES

In addition to the indirect verification using reference blocks and a reference indenter, it is possible to realise the calibration by direct verification of the test force, the indenter, the depth-measuring device and the testing cycle. Some conditions of the calibration process, e.g. the verification range, and the necessary accuracy of the depth-measuring device are described in standard ISO 6508-2. With reference to these parameters, a new depthmeasuring calibration device was developed. The study describes the function of this device and the calibration process. The advantages of this new process are that the measurement takes place in the axis of force application and that the calibration is independent of the Rockwell hardness scales. During calibration, the force stresses the calibration device but not the sensitive measuring sensor. Results of a real depth-measuring device verification are also presented.tion process. The advantages of this new process are that the measurement takes place in the axis of force application and that the calibration is independent of the Rockwell hardness scales. During calibration, the force stresses the calibration device but not the sensitive measuring sensor. Results of a real depth-measuring device verification are also presented.

N. Huber, E. Tioulioukovsski
SMART INDENTATION METHODS: THE APPLICATION OF NEURAL NETWORKS

In the last decade, the nanoindentation technique has become one of the most important characterization methods in micro dimensions. The experimental and analytical techniques have been pushed towards an identification method that can compete with tensile tests. It is self-evident to apply these powerful tools in macro dimensions as well, where the nanoindentation technique has its roots. In this paper a new method is presented how the true stress-strain curve as well as the viscosity and creep behaviour of a given material can be extracted from the indentation curve by using a smart analysis tool based on neural networks. Finite Element simulations are carried out for randomly chosen sets of material parameters and maximum indentation depth. The resulting load-depth and depth-time curves are collected in a database together with the material parameters. With this database neural networks are trained to identify the material parameters from measured load-depth and depth-time curves.

A. Wehrstedt
SITUATION OF STANDARDIZATION IN THE FIELD OF MECHANICAL TESTING AND MEASUREMENTS

Standardized mechanical test methods are referred in many materials and product standards for the characterization of quality of the materials or products. Mechanical testing is carried out on materials for three different reasons: - For quality control purposes to ensure that a material conforms to a technical specification or that it has been correctly processed. - To provide information which can be used in the design of a component or structure. - As part of investigations into the reasons for failures in service. Hence the results achieved from the mechanical testing of products that are made of / or from materials are used to help guarantee the safety and reliability of materials which in turn ensures the safety of those products. The paper gives an overview on the standardization activities of the last ten years for the different fields of mechanical testing as uniaxial, ductility, hardness, toughness and fatigue testing .

A. Stibler, K. Herrmann, Th. Polzin, A. Germak
COMPARISON MEASUREMENTS OF HARDNESS SCALES FOR ESTABLISHING THE HARDNESS STANDARD OF SLOVENIA

A commercial hardness testing machine was provided to represent a hardness reference standard in Slovenia. In order to evaluate how accurate the hardness scales realised with this machine could be, the main influence factors contributing to the uncertainties were verified and comparative measurements carried out, the results of which were compared with several laboratories owning primary hardness standard machines.

R. Affri, G. Barbato, S. Desogus, A. Germak, C. Origilia, D. Perteghella
METROLOGICAL CHARACTERIZATION OF OPTICAL MEASURING SYSTEM FOR HARDNESS INDENTERS

The verification of the geometry of Rockwell indenters has been widely studied in the past and, at the present, it is one of the most important tasks (in the uncertainty budget of hardness measurements) in discussion in many international organizations involved in the hardness field. The new measuring system designed in IMGC and developed in cooperation with AFFRI has been characterized and the results of the calibration are presented. The uncertainty evaluation has been calculated following the ISO guide on uncertainty evaluation. At the end, the results of the intercomparison between the new instrument and the instrument used up to now in IMGC laboratory, completely different from the point of view of measurement methodology, are presented.

D. Schwenk
VARIATION OF THE CALIBRATING VALUE AND THE RANGE DEPENDING ON THE NUMBER OF THE CALIBRATING INDENTATIONS DURING THE ROCKWELL HARDNESS TEST

Represented is the problem at the definition of measure values in the standards from the statistical point of view. The definition of the calibrating of hardness reference blocks in the standards will be translated to a statistical model formulations. The statistical model will be checked by experimental measurements. The problem of the determination of a quality feature for the hardness reference blocks will be discussed.

H. Yamamoto, T. Yamamoto, H. Kawashima, S. Sudoh
HARDNESS TRACEABILITY SYSTEM

As a matter of fact, global standards for hardness testing are set by International Organization for Standardization. The ISO standard for hardness testing consists of three parts: Part 1 is for test methods, Part 2 is for testing machines, and Part 3 is for hardness standard blocks. JIS provides three independent standards, but they have perfect consistency with the three parts of the ISO hardness-testing standard. These standards prescribe that hardness testing machines first be subject to direct verification of their test force, indenter, testing cycle, and hardness indicator, and then that hardness must actually be measured using standardized blocks for indirect verification. This is a globally agreed fact. In this connection, the traceability or the uncertainty of Rockwell hardness has been a topic of international debate. This paper discusses our position on this issue as a manufacturer of hardness standardized blocks.

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