In a previous report, the authors investigated changes in hardness measurements when load rise time (LRT) was changed over a broad range in Vickers harness tests with loads of between 15 kgf and 150 kgf. As a result, we reported that hardness measurements varied according to the LRT value for every test load, while they remained almost constant between 15 kgf to 150 kgf if LRT was the same, although the indentation velocity of the indenter differed by more than three times between the two loads. It is very interesting that the considerable difference in indentation velocity due to varied test loads was not reflected much in hardness measurements. We, therefore, verified the effects of loading speed on hardness measurements theoretically from the strain rates of indentation deformation under the indenter and obtained some findings as follows. (1) It is necessary to define loading conditions to ensure the reliability of hardness blocks (2) The loading condition, namely the strain rate under indentation could be determined by the equation which was newly introduced by the authors. (3) According to this equation, loading conditions for general harness tests could be defined by loading time (LRT) regardless of load values. (4) Also considering that hardness measurements can vary according to load holding time, we may say that testing conditions can be "defined by time,". (5) Consequently, from the viewpoint of industrial practice, it would be reasonable to have rough criteria, that is, for how many seconds the test should be conducted, rather than to have scrutinized discussions on indentation velocity.

Based on the estimation of uncertainty the present requirements of the standard are discussed. Additional requirements needed for improving the reliability and the reproducibility are proposed. Especially the compliance of the machine affects strongly the parameters EIT and HMs in the macro range.

Methods for hardness measurement on elastomers are characterized by a set-up where indenters with various defined geometries are pressed under defined test forces into the surface of testing material. The hardness value represents the resistance of the material to the rigid indenter and is calculated from the indentation depth of the indenter in the to be tested material. The test methods IRHD and Shore are the most common methods used in the field of rubber hardness measurements. Appropriate hardness measuring instruments are spread world wide. A periodic verification has to be carried out to assure the accuracy of these measuring instruments. Direct and indirect verification methods are recommended to be used. For the indirect method rubber hardness reference blocks are used. This indirect verification method is especially appropriate for the daily check of hand held rubber hardness testers. On the other side the direct verification of test force, depth measuring system and indenter geometry is suited for the periodic calibration of rubber hardness testers. For the rubber hardness reference blocks their accurate hardness reference value and the long-term stability are the most important characteristics. In this paper the long-term behaviour of hardness of rubber blocks which at present are available on the market and are made by different producers is presented. For the measurements the Shore and IRHD hardness standard devices in the PTB have been used. In order to determine the relationship between hardness and time under the specified conditions a regression analysis of the obtained measurement results was carried out. The results of this analysis can be used for the improvement of quality assurance systems in the field of rubber hardness measurements.

It is desirable to measure the hardness of individual grains and microconstituents to have control over the mechanical properties of materials. An ultra-micro or nanoindenter is required to make indents small enough to fit inside a single grain or phases that is smaller than 10 mm diameter. Because the indents are too small for an optical microscope an atomic force microscope was used to view the location and measure the contact area. Measuring the contact area of indents from an atomic force microscope image is unreliable because it is difficult to manually locate the indent edge. To solve this problem computerized image analysis software called NanoMc was used to measure the residual indent contact area. This software digitally reconstructed the residual indent back into the fully loaded indentation shape and then measures the contact area and depth. This method avoids the complicated tip rounding and load-frame compliance problems. As an example this method was used to measure the hardness of pearlite and ferrite microconstituents in SAE 1020 steel.

Standard Reference Material (SRM) 2831 was developed to improve Vickers hardness testing of Ceramics and Hardmetals. It may be used with conventional hardness testing machines that make indentations that are measured with an optical microscope. The SRM is a hot-isostatically pressed tungsten carbide with 12 % cobalt disk which has five indentations made at a load of 9.8 N (1 kgf). Each SRM is individually certified for the size of each of the 5 indentations, the average diagonal length ( 35.0 m), and the average hardness HV1. The HV1 is nominally 15 GPa which is in middle of the hardness range for most ceramics and cutting tool carbides.