Correction of squareness measurements of Vickers indenters due to the tilt of the pyramid axis

In Vickers hardness measurements, ISO 6507-2 and 6507-3 Standards require to verify that the quadrilateral of the pyramid indenter base has angles of 90° ± 0.2°. Such measurement is usuallyperformed through optical measuring systems, which, rotating the diamond indenter, allowsto evaluate the angles between two consecutive faces with high accuracy. These angles correspond to the angles of the quadrilateral base when the axis of the pyramidis perfectly perpendicularto the seating surface. Nevertheless, when the pyramid axis is tilted, the angles between two consecutive faces are different from the corresponding angles on the quadrilateral base, thus a correction is required. In this work, a method to correct squareness measurements, based on a geometrical model, is presented

Indentation Modulus, Indentation Work and Creep of Metals and Alloys at the Macro-Scale Level: Experimental Insights into the Use of a Primary Vickers Hardness Standard Machine

open5In this work, the experimental method and the calculation model for the determination of indentation moduli, indentation work, and indentation creep of metallic materials, by means of macroscale-level forces provided by a primary hardness standard machine at the National Institute of Metrological Research (INRIM) at the at room temperature were described. Indentation moduli were accurately determined from measurements of indentation load, displacement, contact stiffness and hardness indentation imaging and from the slope of the indentation unloading curve by apply-ing the Doerner-Nix linear model; indentation work, representing the mechanical work spent dur-ing the force application of the indentation procedure, was determined by calculating the areas un-der the loading–unloading indentation curve, through fitting experimental data with a polynomial law. Measurements were performed with a pyramidal indenter (Vickers test). The applied force was provided by a deadweight machine, and the related displacement was measured by a laser inter-ferometric system. Applied forces and the occurring indentation depths were simultaneously meas-ured: the resulting loading–unloading indentation curve was achieved. Illustrative tests were per-formed on metals and alloy samples. Discussion and comments on the suitability of the proposed method and analysis were reported.openAlessandro Schiavi, Claudio Origlia, Alessandro Germak, Andrea Prato, Gianfranco GentaSchiavi, Alessandro; Origlia, Claudio; Germak, ALESSANDRO FRANCO LIDIA; Prato, Andrea; Genta, Gianfranc

Indentation modulus and Young\u27s modulus of Cu‐Cr‐Zr alloy at macro‐scale level

In this communication the first experimental results of indentation modulus and Young’s modulus (tensile modulus) of seven samples of Cu-Cr-Zr alloy (chemical composition: 1%Cr, 0.06%Zr, rest Cu), in the macro-scale range at room temperature, are presented and compared. Six Cu-Cr-Zr samples have been aged from different heat treatments for 2 hours in a vacuum furnace at 400C, 480C, 550C, 600C, 650C, 700C, and a single sample is kept as received. In the alloys here investigated, Cr is coherent in the Cu matrix for the as-received condition and the precipitates grow in size up to ~32 nm for the 700C condition. The experimental procedures for the measurement of indentation modulus, by using the primary hardness standard machine at INRIM, and the Young’s modulus, by means of engineering tensile tests at CIRA, are described. Please click Additional Files below to see the full abstract

Correction of squareness measurements of Vickers indenters due to the tilt of the pyramid axis

In Vickers hardness measurements, ISO 6507-2 and 6507-3 Standards require to verify that the quadrilateral of the pyramid indenter base has angles of 90° ± 0.2°. Such measurement is usuallyperformed through optical measuring systems, which, rotating the diamond indenter, allowsto evaluate the angles between two consecutive faces with high accuracy. These angles correspond to the angles of the quadrilateral base when the axis of the pyramidis perfectly perpendicularto the seating surface. Nevertheless, when the pyramid axis is tilted, the angles between two consecutive faces are different from the corresponding angles on the quadrilateral base, thus a correction is required. In this work, a method to correct squareness measurements, based on a geometrical model, is presented

Perspectives and limits on the use of commercial low-cost digital MEMS accelerometers in gravimetry

The value of the acceleration due to gravity is of interest in a wide range of fields, from geophysics, geodesy, water-floor monitoring, and hazard forecasting to oil, gas and mineral exploration. For this purpose, relative or absolute gravimeters have been developed and used for decades. While absolute gravimeters are mainly used in monitoring stations or as reference, relative gravimeters are those actually used to determine the relative variations of the local gravitational field given their smaller dimension, lighter weight, and better reading resolution, despite the high costs and the difficulty in being used under severe environmental conditions. In the last years, the advent of micro-electromechanical-systems (MEMS), in particular MEMS accelerometers, has opened up the doors to new measuring possibilities at very low-costs. As a consequence, different international research groups focused their efforts to develop relative MEMS gravimeters and showed that this technology might be really useful for monitoring the gravitational field. However, their current production is limited to a few specimens and prototypes that cannot be exploited on a large scale at the present day. For this reason, this work investigates the possibilities and the limits in the use of commercial digital MEMS accelerometers as relative gravimeters. The digital MEMS accelerometers investigated in this work are two commercial low-cost digital MEMS accelerometers (STM, model LSM6DSR, and Sequoia, model GEA). The first is composed of an accelerometer sensor, a charge amplifier, and an analog-to-digital converter and is connected by a serial cable to a separated external microcontroller (ST, model 32F769IDISCOVERY), in which other electronic components are integrated. The second is composed of the sensing element and the analog-to-digital converter. Both are connected to the computer via USB cable. The two devices are included in a thermally insulated case, in which a resistive heater and a resistance thermometer (PT1000), connected in loop, are placed in order to guarantee temperature stability during use. The system, installed on a tilting table to ensure higher accuracy in the evaluation of local g, is calibrated in static conditions by comparison to the absolute gravimeter IMGC-02 at a specific measurement location at INRIM. Calibration is repeated several times over a period of a few weeks in order to evaluate repeatability, reproducibility and stability over time. Despite the promising future prospects of this technology, at present, the levels of precisions are low compared to the ones required by most of geodynamics applications

MEASUREMENT OF MACRO-SCALE INDENTATION MODULUS USING THE PRIMARY HARDNESS STANDARD MACHINES AT INRIM

In this paper it is described the experimental procedure and the statistical method for the measurement of indentation modulus by using the primary hardness standard machine at INRIM, in the macro-scale range. Indentation modulus is calculated on the basis of Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness and Vickers hardness impression imaging. Load is provided by dead-weight masses and displacement is measured by a laser-interferometric system, perpendicular with respect to the Vickers pyramid vertex. The geometrical dimension of the Diamond Pyramid Hardness (DPH) impression is measured by means of a micro-mechanical system and optical microscopy imaging technique. Applied force and indentation depth are measured simultaneously, 16 Hz of sampling rate, and the resulting indentation curve is obtained. Preliminary tests are performed on metals and alloys samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed

Treatment with 1,25-dihydroxyvitamin D3 preserves glomerular slit diaphragm-associated protein expression in experimental glomerulonephritis

In this study, we investigated the effect of 1,25(OH)2D3on proteinuria and on the alteration of slit diaphragm-associated proteins induced by anti-Thy 1.1 in Wistar rats. Four groups of animals were studied: group I, anti-Thy 1.1 treated rats; group II, anti-Thy1.1 treated group that at day 2, after the onset of overt proteinuria, started the treatment with 1,25(OH)2D3; group III, normal control rats injected with vehicle alone; group IV, rats that received only 1,25(OH)2D3. At day 2, in group I and II, before the administration of 1,25(OH)2D3, protein excretion was significantly increased when compared to controls. Overt proteinuria was maintained until day 14 in group I whereas in group II protein excretion was significantly reduced from day 3 to day 14. Moreover, treatment with 1,25(OH)2D3abrogated podocytes injury, detected as desmin expression and loss of nephrin and zonula occludens-1 (ZO-1), two slit diaphragm-associated proteins, and glomerular polyanion staining, that were observed in group I. In conclusion, these results suggest that 1,25(OH)2D3administrated with a therapeutic regiment may revert proteinuria, counteracting glomerular podocyte injury