الفهرس | Only 14 pages are availabe for public view |
Abstract The dynamic force transducers parameters (stiffness, damping coefficient, and head mass) are important in determining the frequency range of each force transducer used at the different dynamic setups. Since the force transducer sensitivity is changed greatly after the resonance frequency. The aim of the present study is to demonstrate two new measurement methods in measuring the parameters of the dynamic force transducers under applying static force and creep. These new approaches are distinguished by their stability and accuracy as they depend on using primary measurement devices precisely assembled; dead weight machine and laser interferometer device. An impulse dynamic force calibration machine at the National Institute of Standards (NIS) in Egypt has been developed in this study to apply a complete calibration including measuring the parameters of force transducers beside their dynamic sensitivity. As the machine becomes including air bearings as a guide for the falling mass and an accelerometer for measuring its acceleration. Also, the distance between the force transducer and the falling mass has become more precisely adjusted using a micrometer. The force transducer parameters measured under applying these different measurement methods have been compared with each other and compared to those parameters measured under applying sinusoidal dynamic force for validation. The sinusoidal dynamic force measurement method has been introduced there as a measurement service in Germany at the PhysikalischTechnische Bundesanstalt (PTB). Also, the two measurement methods of the force transducers parameters under applying static force and creep have been carried out at PTB. The dynamic sensitivity, for one of the force transducers under study, is measured using the impulse method. Then it has been compared by its static sensitivity. The analytical investigations showed that the new measurement techniques (static and creep) for the force transducers parameters presented in this study are promising. As their results are reliable, and accurate using simple mechanisms instead of complex dynamic systems. There is a sensible difference between the stiffness values of the force transducers measured under applying the sinusoidal dynamic measurement method and the other measurement methods in this study. This difference in case of the 20 kN force transducer reached 22.88% and in case of the 5 kN force transducer reached 19.65%. On the other hand, small and insignificant differences of the stiffness are observed between the other three measurement methods. These differences are about 0.07%, and 0.278% in case of the 20 kN, and 5 kN force transducers respectively. An obvious but not significant differences have been observed between the various methods of measurement for the damping coefficient results. By comparison to the creep measurement method, this differences in damping coefficient ranged from -31.4% to -1.62% for the two force transducers. A small difference (3.2%) is observed between the sensitivity of the force transducer measured under applying the impulse dynamic calibration method and the static calibration method. More and above to the static and the creep measurement methods, the impulse dynamic calibration machine at NIS has been well developed and can be used in the dynamic calibration. Rocking modes, and introducing the adapter which links the electrodynamic shaker with the force transducer are factors that affect the accuracy of the force transducer’s parameters values in the sinusoidal dynamic measurements. |