EMRP-SIB63: Force Traceability within the Meganewton Range

• Forschungsstelle: METAS
• Projektnummer: F-5133.30027
• Projekttitel Englisch: EMRP-SIB63: Force Traceability within the Meganewton Range

Schlüsselwörter (Englisch)

Force, metrology, meganewton

Kurzbeschreibung (Englisch)

In mechanical engineering, aerospace industry, energy industry, building industry, safety
engineering and testing, forces with nominal values of 15 MN and more have to be measured.
The application of force measuring devices can be totally different from their calibration.
Traceable calibrations of suitable transfer standards should improve the measurement
of forces in industrial applications. To reduce the uncertainty of measurement in practical
applications, parasitic components and effects that are related to real loading procedures
which might be very different from the static calibration procedures, have to be taken into
account. Furthermore, the force range should be extended to larger nominal values. It is estimated
that there is a need to measure forces up to 30 MN.
Therefore, newly developed force transfer standards with highest nominal values have to be
investigated in order to improve the measurement of forces and the dissemination of the
quantity of force. Thus, parasitic components and different loading effects will be analyzed to
consider these effects when the device is used in industrial applications.
In the highest force range, build-up systems are used and the question about the uncertainty
evaluation of such systems arises. Here it is necessary to provide the user with procedures
on how to use this kind of force measurement devices in this range and offer the corresponding
methods of uncertainty calculation.

This project is part of the European Metrology Research Programme (EMRP, http://www.euramet.org/index.php?id=emrp); it is partly funded by the European Union on the basis of Decision No 912/2009/EC.

Projektziele (Englisch)

The project addresses the following scientific and technical objectives:

• To extend the range of primary force standards to cover the range from 1 MN to 30 MN or furthermore up to 50 MN, with uncertainties of the order of 0.002 % up to 2 MN, 0.01 % up to 15 MN and 0.05 % up to 30 MN.
• To develop improved transfer standards for forces up to 30 MN, in order to enable both more reliable dissemination of the unit of force and improvements in the measurement of force in industry. The effect on the overall uncertainty during use due to parasitic components and loading procedures that are different to the static calibration procedure should be evaluated.
• To develop methods to determine the uncertainty of the whole measurement system of high force range build-up systems.
• To develop methods to extrapolate calibration results for values higher than 15 MN, including evaluation of the associated uncertainties.
• To develop new procedures and EURAMET technical end user guidelines for the use of high force measurement devices and the methods of uncertainty calculation. This includes improvements in the dissemination of the force unit from primary standards to calibration services and testing laboratories.

Abstract (Englisch)

METAS was involved in the numerical modelling of sensors and build up systems and in the time loading effect. The work in the field of numerical simulation allowed us to demonstrate the influence, on the hysteresis, of the contact force, between the load pad and the sensor and between the sensor, and the base plate. We have also demonstrated the importance of the position of the strain gauge in order to be influenced as less as possible by changes of conditions at the interface between the sensor and the outer world. Numerical simulations made by METAS using the software Comsol MultiPhysics have been used to validate the simulation of sensors and build up systems made at the PTB with the software Ansys.

Measurements performed on a build-up system of 3 sensors on loan from EMPA allowed to demsonstrate the similarities of the measurements with the numerical simulations. We have been able to validate the small influence of the non-parallelism of the plates of the force machine on the measurement results obtained with a build-up System. Measurements performed in our laboratory within the work package “time loading effect” have been used to optimize and correct the hysteresis. Unfortunately only the measurements performed on the dead weight system have been used because the effect and the way the force was ramped up on the 2 MN system was difficult to model correctly.

Umsetzung und Anwendungen (Englisch)

The METAS force laboratory is better equipped today to understand the cause of hysteresis of a force sensor and to take correct measures in order to reduce its influence on the uncertainty. We have been able to understand the correct measures to be taken on the contact surfaces, with the table or the load pad, in order to achieve reproducible measurements. We are able to compensate the hysteresis in the case it is reproducible. We have demonstrated the consistency of the response of a force sensor isolated or integrated in a build-up system. A network within the EURAMET community active in force and within the industry was built up.

Publikationen / Ergebnisse (Englisch)

Rolf Kumme, Force Traceability within the Meganewton Range, IMEKO 22nd TC3, 15th TC5 and 3rd TC 22 International Conferences, Cape Town, Republic of South Africa, 3 to 5 February, 2014.