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C. Ferrero, C. Marinari
CHARACTERISATION OF REFERENCE TORQUE WRENCHES BY THE IMGC SIX-COMPONENT CALIBRATION SYSTEM

This paper describes the metrological characterisation of two Reference Torque Wrenches (RTW) of 100Nm and 500Nm capacity. The characteristics of the torque sensors were evaluated by using the IMGC-CNR sixcomponent calibration system (EUROMET agree facility, project 113). The repeatability of the absolute variation of the output signal of the two TTS under the application of the different spurious components, referred to the R.O., is in general of the order of 5·10–5. The sensitivity to spurious components are normally better than 2·10–3 of the nominal torque.

Carlo Ferrero, Carlo Marinari
THE DISSEMINATION OF THE FORCE UNIT IN ITALY: CALIBRATION OF MATERIAL TESTING MACHINE INTERCOMPARISON

One of the most important activities at European (EA) and National level of the National Accreditation Body (NAB) is the organisation of a series of interlaboratory comparisons (ILC), to verify the measurements capability of the calibration laboratories. In 2001 one ILC, for the calibration of uniaxial testing machines, was organised in Italy by SITIMGC with the IMGC-CNR as reference laboratory. In the present paper the main results obtained during the ILC are discussed, in particular a regression analysis was applied to evaluate the differences on the repeatability and accuracy given by the different laboratories.

Kamlesh K. Jain, S.K. Jain
BEST MEASUREMENT CAPABILITY OF THE NEWLY DEVELOPED 5 kN DEAD WEIGHT FORCE MACHINE

This paper describes the salient features and the results of metrological performance of the newly developed 5 kN dead weight force calibration machine. Two well characterized strain gauge force transfer standards of 2 and 5 kN full capacity having repeatability better than 0.002% in compression mode were used to derive the best measurement capability of ± 50 ppm (k = 2) of the machine.

Jin-Wan Chung, Kyung-Ho Chang, Woo-Gab Lee, Kwang-Pyo Kim
AIR DENSITY DETERMINATION USING 1 KG BUOYANCY MASS COMPARISON(III)

In calibration of secondary 1 kg stainless steel mass standard from a platinum-iridium kilogram prototype, a major uncertainty arises from the measurement of air density for the buoyancy correction. This paper is continued to the reference. An experimental determination of air density using buoyancy pairs and a vacuum balance has been carried out and its results were compared with those of the CIPM formula 81/91. The environmental measurement instruments used for this experiment are different from those previously used. Also the true mass difference between buoyancy pairs in vacuum was measured at mass laboratory of NMIJ in Japan and compared with the KRISS result. The disagreement between air density measurements by the 1 kg BA-pair and those by CIPM formula is 5.1 x 10-4 kg/m³, but the standard deviation of the difference between both methods has been improved, to 5.3 x 10-5 kg/m³ compared to 1.5 x 10-4 kg/m³ by the previous experiment.

Miroslav Kopecky, Ivan Letko, Vladimir Cuth, Jan Vavro
TESTING EQUIPMENT FOR FATIGUE TESTS OF STEEL CORDS

The contents of the paper point out the necessity of combining the theoretical and experimental approaches in the investigation of tyre load in vehicles. The models are planar and they model the cross-section of the tyre enabling the consideration of the bottom load and the internal pressure in the tyre, as well as the influence of the lateral force. The paper presents the findings, the formulations necessary for solving the task obtained in the experimental model tests and serving as a basis for comparison with the results obtained from purely theoretical approaches, e.g. by the method of finite elements, with identical load conditions.

Jongho Kim, Yonkyu Park, Daeim Kang
DESIGN AND FABRICATION OF A THREE-COMPONENT FORCE SENSOR USING MICROMACHINING TECHNOLOGY

This paper describes a design methodology of a tri-axial silicon-based force sensor with square membrane by using micromachining technology (MEMS). The sensor has a maximum force range of 5 N and a minimum force range of 0.1 N in the three-axis directions. A simple beam theory was adopted to design the shape of the micro-force sensor. Also the optimal positions of piezoresistors were determined by the strain distribution obtained from the commercial finite element analysis program, ANSYS. The Wheatstone bridge circuits were designed to consider the sensitivity of the force sensor and its temperature compensation. Finally the process for microfabrication was designed using micromachining technology.

Leonardo D’Acquisto, Roberto Montanini
DESIGN AND SET-UP OF A BI-PENDULUM IMPACT TESTING MACHINE

In this work the design and set-up of a bi-pendulum testing rig able to perform low-velocity impact measurements on small and medium-size components is reported. Experimental tests were conducted both to check the theoretically calculated value of the equivalent impacting mass and to quantify the overall energy losses during the idle movement of the mass. In order to provide useful information on the material behaviour during a crash test, the impact testing machine has been instrumented with different sensors: a piezoelectric accelerometer placed on the impact mass to measure the horizontal acceleration, an optical sensor to measure the initial impact velocity, a piezo film load cell, developed by the Authors, placed on the sample holder block, to measure the impact force directly on the specimen.

Andreas Lindau, Rolf Kumme, Andrea Heiker
INVESTIGATION IN THE LOCAL GRAVITY FIELD OF A FORCE LABORATORY OF PTB

It belongs to the functions of the National Institutes of Metrology to realise a force scale of highest accuracy. The uncertainty of the resulting force basically depends on the precise knowledge of local gravity acceleration. This paper describes the spatial determination of the local gravity field in the force laboratory of the PTB on the basis of a new highly precise gravity network. A special emphasis is placed on the influence due to gravity of the surrounding masses placed in the laboratory on the single gravity value. It can be shown that the installation of the new 2 MN deadweight force standard machine has led to a significant change in the local gravity field. Temporal variations caused by earth tides are proved by long-term registrations and are considered in a correction term for the gravity value. The periodical change of gravity reaches a level of 10-7 g in the equator region and at present does not affect the uncertainty budget of the force measurement.

Dan Mihai Stefanescu, Tiberiu Manescu
MULTI-COMPONENT FORCE AND TORQUE BALANCES FOR WIND TUNNELS

Starting from the German experience in the field of electrical measurement of mechanical quantities, one of the top application is the six-component measuring of the aerodynamic load torsor. For these complicated mechatronic devices, which have to measure six widely different components with the same relative accuracy, a complex mechanical and electrical analysis has been performed concerning the optimum positioning and connecting of the strain gauges, in order to increase the sensitivity and to compensate the disturbing influences. Four original strain gauged multicomponent balances for scale model testing were designed and manufactured having in view the improvement of the road vehicle and aircraft performances. Concrete data are shown in the four figures and tabularly summarized.

Weilu Shang, Yan Wang, Tao Li, Zhaojun Qian, Dongsheng Zhang, Mingbang Lin
ELIMINATING THE ADDITIONAL INERTIA IN MEASURING THE NATURAL FREQUENCY OF A TORQUE SENSOR

In measuring the natural frequency of a torque sensor, one must apply excitation through some mechanism which produces additional inertia coupling to sensor that the original or instinct data can not be gotten. A method was developed which can eliminate these inertia by testing and calculating. The principle, experimental method, instrumentation and results were described in detail in this paper.

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