Bruno Andò, Pietro Giannone, Salvatore Graziani, Nicola Pitrone
MEASUREMENT SYSTEM FOR THE CHARACTERIZATION OF PIEZOELECTRIC BIMORPHS

Hysteresis is a common phenomenon in various non linear systems including piezoceramic materials. Piezoelectric bimorph devices show hysteretic behaviour, when operating as actuators. In this paper an experimental set-up to investigate the hysteretic behaviour of a PZT is described. The strategy adopted uses a resistive readout scheme and a CCD tool for the system calibration. Moreover, software tools have been developed to manage the experimental and to process signals coming from the hardware developed.

Thomas Bruns, Michael Kobusch
DATA ACQUISITION AND PROCESSING FOR PTB'S IMPACT FORCE STANDARD MACHINE

The 20 kN Impact Force Standard Machine (IFSM) of PTB’s working group “Impact Dynamics” is supposed to provide traceability for dynamic force by measuring the acceleration of a steel body using a laser-Doppler-interferometer (LDI) [1]. The acceleration itself is derived from time dependant velocity data by numerical differentiation, which is a process prone to noise amplification. Therefore a thorough investigation of the data flow and data analysis algorithms concerning robustness, accuracy and the proliferation of disturbances is necessary. This paper describes the data acquisition system together with three different algorithms for digital demodulation of the LDI signal with regard to the boundary conditions given by the parameters of the equipment.

V. Tsymbalyuk, J. Linhart
CORRECTIONS OF AERODYNAMIC LOADINGS MEASUREMENT ON AIRFOIL CASCADE AT BENDING-TORSION VIBRATIONS

The paper describes improvement of the unsteady aerodynamic forces and moments measurements in an airfoil cascade. These loads are caused by shifting and angular vibrations of airfoils. The improvement was achieved by taking airfoils and other elements deformations, induced by action of innercia and measured aerodynamic firces, in consideration during the calibration and measurement process. The different variants of airfoils supporting are considered.

Sinan Fank
INFLUENCE OF MICROSTRUCTURAL CHANGE IN AISI 4340 STEEL SPRING MATERIAL HAVING IDENTICAL HARDNESS LEVEL ON THE HYSTERESIS ERROR OF FORCE TRANSDUCER

Different heat treatment processes can be applied on the spring element of a force transducer in order to obtain good and satisfactory performance. The manufacturers are generally focused on the improvement of performance by applying different heat treatments on spring material, and no information is in free circulation regarding the process-performance relationships of transducers due to tight competition in the market. The study covers the attempts of different heat treatments on spring element using AISI 4340, which is regarded as one of the best spring materials for force transducer applications. The steel was quenched and tempered at predetermined temperature, and 45 Rockwell-C hardness values was reached to obtain fine martensite structure. In order to obtain coarse martensite structure having identical hardness from spring material, some specimens were subjected to high temperature during austenite transformation in 1000°C in 4.5 hours priority. In order to produce bainitic structure different heat treatment was applied on the specimens to have identical hardness level. It was observed that different heat treatments influenced the transducer performance, particularly hysteresis behaviour point of view. To minimize the hysteresis error of force transducers has prime concern and best result was obtained in the bainitic- structured specimen. After building the force transducers with differently heat-treated spring materials, their performances were recorded by using a dead weight force standard machine, concentrating on hysteresis characteristics. The results were compared with each other and analysed regarding the structural properties of spring materials and a process path was proposed to obtain the best performance in force transducers.

Levent Yagmur, Sevda Kacmaz
ENDURANCE TESTING MACHINE FOR NONAUTOMATIC WEIGHING INSTRUMENTS

A machine was designed and manufactured for endurance tests of nonautomatic weighing instruments according to the regulation of OIML R76-1-2 and EEC/90/384. An AC servomotor directly actuates the machine. It has also control panel and software. It has a compact module consisting of ball screw mechanism and a handler, made of polyamide material, specially designed. It is used for handling nine numbers of standard masses, knops headed type, with ranges 100 g up to 50 kg. There are nine types of weight carriers for each different mass. Some parameters for loading and unloading of masses can be set to desired values within limits by using control panel. The velocities of loading and unloading of masses and also standing time of mass on the instrument can be adjusted. All parts of movable section of the machine were enclosed by using plexiglas material for preventing. The machine is capable of 100.000 and more times fully automatically loading and unloading of 9 (nine) types of standard masses on to the instrument. It can also be modified to another standard masses not in range 100 g to 50 kg.