9762 papers found
This paper details work carried out to determine the influence of indenter geometry on measured hardness values for both Vickers and Rockwell hardness methods. For Vickers Hardness, the effect of indenter angle is quantified, and for Rockwell Hardness, the effect of varying both cone angle and tip radius is investigated.
As part of a project to produce primary hardness reference blocks for the Rockwell B hardness scale at the National Institute of Standards and Technology (NIST), studies were conducted to observe the stability of the hardness value of the blocks over a period of time and with use. A study of brass test blocks at the 42 HRBW level revealed some interesting instability results when tested using the NIST standardizing machine with it’s large diameter sample support. After a relatively small number of indentations, each block exhibited an abrupt change in the apparent hardness of the test block....
Design specifics and study results are provided for the new National Shore D scale hardness standard. At the metrological study of the standard the calculations of uncertainty in measurements with two methods are considered: in accordance with the international guide on expression of uncertainty in measurement and in accordance with the principles based on the scales of order properties. According to the metrological study, the standard ensures the reproduction and dissemination of the scale in the actually used range of HSD numbers of 20 to 102 with an HSD uncertainty of no more than 0.5.
A commercial hardness testing machine has been provided to represent a reference hardness standard in Slovenia. Various hardness scales which are important for calibration purposes are realized on this machine. The evaluation of measurement uncertainty is one of the most important tasks for establishing this reference standard. Therefore the influence quantities contributing to the uncertainty are determined and the calibration of the machine by direct and indirect method is carried out. Calculations of measurement uncertainties for Brinell, Vickers and Rockwell hardness scales are...
Methods of structural strength and lifetime control for short and safe components are traditionally based on the most structural and functional materials. Mechanical tests do not give a reliable data because of inconsistency of wear and fracture mechanism of specimens and real structural members. For the structural members the essential charges of anisotropy (texture) of the initial material occur after various technological operations. Because of this it is necessary to develop nondestructive methods of structure control of structural members under loading directly in technological process,...
ISO standards for hardness are established from metrological standards for force, length, etc. and daily control requirements via hardness standard blocks. The authors have already stated that the unification of loading speed via ISO standards is important both industrially and economically. In consideration of the international importance of ISO standards for hardness testing, the authors review the current ISO specifications in this report, particularly their definition of loading speed, tolerances for Rockwell reference loads, and other test-block requirements, based on our own...
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.
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...
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...
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...