The Sixth International Comparison of Absolute Gravimeters was held from 5 June to 28 August 2001 at the Bureau International des Poids et Mesures (BIPM), Sèvres. Seventeen absolute gravimeters were used to make measurements at five sites... more
The Sixth International Comparison of Absolute Gravimeters was held from 5 June to 28 August 2001 at the Bureau International des Poids et Mesures (BIPM), Sèvres. Seventeen absolute gravimeters were used to make measurements at five sites of the BIPM gravity network. The vertical gravity gradients at the sites and the ties between them were also measured using seventeen relative gravimeters. For the first time the ties were also measured using absolute gravimeters. Various methods of processing the absolute and relative data were tested to calculate the results. The final results of ICAG-2001 are presented. The acceleration due to gravity at a height of 0.90 m is given as (980 925 701.2 ± 5.5) µGal* and (980 928 018.8 ± 5.5) µGal for sites A and B, respectively, calculated using a combined adjustment of the absolute and relative data.
- by Laurent Longuevergne and +4
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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... more
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.
- by Alessandro Germak and +1
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Title: Absolute gravity stations in Africa. Authors: Mäkinen, J.; Asabir, J.; Francis, O.; Germak, A.; Hinderer, J.; Kroner, C.; Merry, C.; Wilmes, H. ... Publication: EGU General Assembly 2009, held 19-24 April, 2009 in Vienna, Austria,... more
Title: Absolute gravity stations in Africa. Authors: Mäkinen, J.; Asabir, J.; Francis, O.; Germak, A.; Hinderer, J.; Kroner, C.; Merry, C.; Wilmes, H. ... Publication: EGU General Assembly 2009, held 19-24 April, 2009 in Vienna, Austria, abstract #EGU2009-13004. ...
- by Jaakko Mäkinen and +2
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The Martens Hardness (HM) is an important parameter characterising the elasticplastic properties of the to be investigated sample material which is derived from the instrumented indentation test. At present the standardisation of the... more
The Martens Hardness (HM) is an important parameter characterising the elasticplastic properties of the to be investigated sample material which is derived from the instrumented indentation test. At present the standardisation of the instrumented indentation test in the framework of ISO/DIS 14577-1, -2, -3 is underway [1]. This standard addresses the macro-, micro-and nanorange of the indentation test. The peculiarities of the nanoindentation test when measuring samples with thin coatings (coating thickness d < 2 µm) will be considered in ISO/CD 14577-4 for which inputs came from CEN TC 184/WG 5 [2] and from the EU-project "INDICOAT" . Martens Hardness presents a number of advantages, but, as any newly defined method, requires a general analysis of influence quantities to determine the sensitivity coefficients necessary for the uncertainty evaluation. Indentation velocity was found to be one of the main influence quantities for Rockwell and Vickers scales, therefore its effect was evaluated in a previous work that indicated an effect much higher than expected. In that work some warning was given, because the analysis was based on the results obtained on a single Hardness Standard Machine, moreover based on a simple experimental plan that did not guarantee any separation of the effects of time and velocities. In the present work these drawbacks are overcome. The analysis is based on an experimental plan that takes into account the load increasing time, the velocity of the initial part of indentation and the velocity of the last part of indentation, that is for the Rockwell and the Vickers method the most important influence factor. Moreover, following the resolution adopted within the recent ISO TC 164/SC3 meeting during which Martens Hardness was extended to cover from nano to macro ranges, experiments are performed on each of these ranges and with different machines, delivering in that way more significant results.
One of the main problems related to Rockwell hardness measurements is the influence of the indenter shape. In the present work the effects of the macro-geometry of the diamond indenter are analyzed as influencing parameters in Rockwell C... more
One of the main problems related to Rockwell hardness measurements is the influence of the indenter shape. In the present work the effects of the macro-geometry of the diamond indenter are analyzed as influencing parameters in Rockwell C test. Both an experimental analysis is carried out, using IMGC National Standard Machine, and a finite element simulation (FEM) is performed. Four different theoretical models are proposed to interpret experimental results: the first model is based on Brinell definition of hardness, the second on Meyer analysis and the last two are based on the evaluation of the deformation work through the analysis of the indentation volume. These different corrections are compared to evaluate their performances.
- by Alessandro Germak and +1
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A low-finesse Fabry-Pérot interferometer is used to determine long and fast displacements. Two corner cube reflectors form the traveling-wave cavity and one beam splitter couples the input collimated laser beam. Given the retrodirective... more
A low-finesse Fabry-Pérot interferometer is used to determine long and fast displacements. Two corner cube reflectors form the traveling-wave cavity and one beam splitter couples the input collimated laser beam. Given the retrodirective property of corner cube reflectors, the cavity operates at the edge of stability over an extended scanning range. The in-line scheme with a single fixed optical component makes the proposed interferometer robust and easy to align and use. These characteristics are particularly useful in applications running in noisy environments, such as in on-field absolute gravimetry. Experimental data showing the performances reached in a transportable ballistic gravimeter are also presented.
We report on the comparison between three absolute gravimeters that took place in April 2010 at Laboratoire National de Métrologie et d'Essais. The three instruments (FG5#209 from METAS, Switzerland, IMGC-02 from INRIM, Italy, and CAG... more
We report on the comparison between three absolute gravimeters that took place in April 2010 at Laboratoire National de Métrologie et d'Essais. The three instruments (FG5#209 from METAS, Switzerland, IMGC-02 from INRIM, Italy, and CAG from LNE-SYRTE, France) rely on different methods: optical and atomic interferometry. We discuss their differences as well as their similarities. We compare their measurements of the gravitational acceleration in 4 points of the same pillar, in the perspective of an absolute determination of g for a watt balance experiment. The three instruments performed repeatable g measurements, but do not agree at the level aimed for. This work calls for additional studies on systematic effects.
The aim of this round robin test was to discover what needs to be done to achieve the world- wide unification of Rockwell hardness scales using diamond indenters (HRC, HRA, HRD, HR15N, HR30N and HR45N) (1) - (5). These scales are the most... more
The aim of this round robin test was to discover what needs to be done to achieve the world- wide unification of Rockwell hardness scales using diamond indenters (HRC, HRA, HRD, HR15N, HR30N and HR45N) (1) - (5). These scales are the most commonly used and their unification is of high industrial importance. The current degree of unification at an international level was assessed by conducting a round robin test. Seventy four specially developed hardness test blocks were all calibrated by twelve laboratories in eleven countries and the results were compared. Test parameters were specified that were more precise than those required by the standards (1). The indenters used to make hardness measurements have a significant effect on the measured result. To separate these indenter effects, measurements were made using common indenters as well as the indenters normally used by the laboratories. Partners for the round robin test
The influence of Rockwell and Vickers diamond indenters geometry in hardness measurements justifies the strict specifications and tolerances in the relative standards. Many methods, and consequently dedicated instruments, have been... more
The influence of Rockwell and Vickers diamond indenters geometry in hardness measurements justifies the strict specifications and tolerances in the relative standards. Many methods, and consequently dedicated instruments, have been developed to investigate the geometrical parameters in order to calibrate the diamond indenters. Most of them, using contact or contactless methods, can only investigate some profiles of the indenters; from these partial measurements the whole geometry is derived. Few other instruments can investigate the whole shape but, since they are custom-developed, costs and difficulties in the calibration of these instruments have limited their use.
Since the 1st International Comparison of Absolute Gravimeters (ICAG) and accompanying Relative Gravity Campaign (RGC) held at the BIPM in 1981, repeated ICAG-RGCs have been organized every four years. A total of 19 absolute gravimeters... more
Since the 1st International Comparison of Absolute Gravimeters (ICAG) and accompanying Relative Gravity Campaign (RGC) held at the BIPM in 1981, repeated ICAG-RGCs have been organized every four years. A total of 19 absolute gravimeters (AG) and 15 relative gravimeters (RG) participated in the 7th ICAG-RGC, which took place in 2005. Co-located absolute and relative gravity measurements as well as precision levelling measurements were carried out.
- by Alessandro Germak and +1
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The Bureau International des Poids et Mesures (BIPM), Sèvres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005. ICAG 2005 was... more
The Bureau International des Poids et Mesures (BIPM), Sèvres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005. ICAG 2005 was prepared and performed as a metrological pilot study, which aimed:
Absolute gravity measurements are based on the reconstruction of the free-falling motion of a test body in vacuum. In this paper, two large disturbing effects are studied, namely the non-gravitational accelerations originated by rotation... more
Absolute gravity measurements are based on the reconstruction of the free-falling motion of a test body in vacuum. In this paper, two large disturbing effects are studied, namely the non-gravitational accelerations originated by rotation and translation of the flying body. Their contribution to the uncertainty of the free-fall acceleration is evaluated using the Monte Carlo method as proposed in Supplement 1 to the GUM. The analysis is specifically applied to the IMGC-02 absolute gravimeter, but can be easily extended to other instruments, including cold-atom gravimeters currently under development.
- by Alessandro Germak and +1
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The Sixth International Comparison of Absolute Gravimeters was held from 5 June to 28 August 2001 at the Bureau International des Poids et Mesures (BIPM), Sèvres. Seventeen absolute gravimeters were used to make measurements at five sites... more
The Sixth International Comparison of Absolute Gravimeters was held from 5 June to 28 August 2001 at the Bureau International des Poids et Mesures (BIPM), Sèvres. Seventeen absolute gravimeters were used to make measurements at five sites of the BIPM gravity network. The vertical gravity gradients at the sites and the ties between them were also measured using seventeen relative gravimeters. For the first time the ties were also measured using absolute gravimeters. Various methods of processing the absolute and relative data were tested to calculate the results. The final results of ICAG-2001 are presented. The acceleration due to gravity at a height of 0.90 m is given as (980 925 701.2 ± 5.5) µGal* and (980 928 018.8 ± 5.5) µGal for sites A and B, respectively, calculated using a combined adjustment of the absolute and relative data.
- by Alessandro Germak and +4
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In the framework of the research activity carried on at the Institute of Metrology G. Colonnetti CNR-Turin and concerning the development of the IMGC02 absolute gravimeter, a new method to estimate time occurrences of interference fringes... more
In the framework of the research activity carried on at the Institute of Metrology G. Colonnetti CNR-Turin and concerning the development of the IMGC02 absolute gravimeter, a new method to estimate time occurrences of interference fringes was developed, tested and finally adopted.
- by Alessandro Germak and +1
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The perturbations of the gravitational field due to the mass distribution of an absolute gravimeter have been studied. The so called Self Attraction Effect (SAE) is crucial for the measurement accuracy, especially for the International... more
The perturbations of the gravitational field due to the mass distribution of an absolute gravimeter have been studied. The so called Self Attraction Effect (SAE) is crucial for the measurement accuracy, especially for the International Comparisons, and for the uncertainty budget evaluation. Three instruments have been analysed: MPG-2, FG5-238 and IMPG-02. The SAE has been calculated using a numerical method based on FEM simulation. The observed effect has been treated as an additional vertical gravity gradient. The correction (SAC) to be applied to the computed g value has been associated with the specific height level, where the measurement result is typically reported. The magnitude of the obtained corrections is of order 1 × 10 −8 m/s 2 .
We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared.... more
We present the results of the third European Comparison of Absolute Gravimeters held in Walferdange, Grand Duchy of Luxembourg, in November 2011. Twenty-two gravimeters from both metrological and non-metrological institutes are compared. For the first time, corrections for the laser beam diffraction and the self-attraction of the gravimeters are implemented. The gravity observations are also corrected for geophysical gravity changes that occurred during the comparison using the observations of a superconducting gravimeter. We show that these corrections improve the degree of equivalence between the gravimeters. We present the results for two different combinations of data. In the first one, we use only the observations from the metrological institutes. In the second solution, we include all the data from both metrological and non-metrological institutes. Those solutions are then compared with the official result of the comparison published previously and based on the observations of the metrological institutes and the gravity differences at the different sites as measured by non-metrological institutes. Overall, the absolute gravity meters agree with one another with a standard deviation of 3.1 µGal. Finally, the results of this comparison are linked to previous ones. We conclude with some important recommendations for future comparisons.
- by Alessandro Germak and +2
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Recently, in the framework of the Working Group on Hardness (WGH) of the Consultative Committee for Mass and Related Quantities (CCM) of the Comité International des Poids et Mesures (CIPM), the opportunity to improve the definitions of... more
Recently, in the framework of the Working Group on Hardness (WGH) of the Consultative Committee for Mass and Related Quantities (CCM) of the Comité International des Poids et Mesures (CIPM), the opportunity to improve the definitions of the hardness scales has been discussed. In this paper is investigated, from the theoretical point of view, the benefits in terms of decreasing of uncertainty subsequently to the approval of new definitions. The analysis will be done on the most important Rockwell, Vickers and Brinell hardness scales, but it will be possible to extend the benefits easily to all other scales.