9762 papers found
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.
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...
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.
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...
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.
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.
The paper faces the problem of recording and analyzing the sensory potentials evoked by tactile stimuli in a non-invasive way. These signals present a very low SNR. Therefore, at now, this very selective investigation technique requires harmful needle electrodes to acquire them. The paper proposes both a new recording method based on surface electrodes and a signal processing technique. This technique greatly improves the SNR of the signals. The new method has been validated measuring the latency on simulated as well as actual signals. The results of the validation phase are presented and...
A numerical model of a general purpose commercial equipment for current versus voltage (I-V) and differential capacitance versus voltage (C-V) measurement of active devices is presented. The good agreement between the model results and experimental data show that the model takes into account the main error sources of the instrument and can be used as a base to perform error correction and to implement a calibration procedure.
A high bandwidth power transducer, based on an inexpensive, commercially available, standard IC package covering frequency ranges from DC to 100 kHz is described. The power transducer can be used for accurate power measurements with distorted waveforms and at high frequency.
The inrush currents generated during a energization of power transformer can reach very high values and may cause many problems in power system. In this paper method for controlled energization of power transformer based on measuring of remanent flux of magnetic core is presented. The remanent flux is measured and memorized at the last de-energization of transformer and then applied at next energization. Experimental results of inrush currents at controlled energization of transformer are presented.