Abstract
The presented paper is focused on embedding of the serially manufactured piezo-electric impact loadcell into Open Hopkinson Pressure Bar (OHPB) and it’s modifications for a direct force measurement during dynamic loading. Conventionally, during the SHPB test dynamic force equilibrium is investigated by a comparison of the transmitted signal wave and the difference between the incident, reflected and transmitted signals measured by strain gauges [1]. However, in the experiments with specimens with low mechanical impedance, a major portion of the incident wave is reflected back on the interface between the bar and the specimen. Comparison between two-large amplitude incident and reflected pulse and a small-amplitude transmitted pulse can be influenced by large error and resulting force equilibrium can be inaccurate. Therefore, a piezo-electric quartz impact force transducer was used to directly measure the axial forces in the vicinity of the specimen end surfaces.
Highlights
Over the past decades, dynamic mechanical testing become widely used method for determination of properties of modern materials (e. g. metal foams, laser sintered structures)
This paper presents embedding of the serial manufactured piezoelectric impact load cell into OHPB (Open Hopkinson Pressure Bar) and its calibration using two pairs of strain gauges as reference sensors
The load cell accuracy is limited by the type of strain gauges used to calibrate it.it is not possible to reach higher precision with load cell than with strain gauges
Summary
Dynamic mechanical testing become widely used method for determination of properties of modern materials (e. g. metal foams, laser sintered structures). Reliable recording of the dynamic response of the material during impact testing is essential for obtaining required material properties at high strain rates. The strain gauges are one of the most commonly used sensors in dynamic testing devices G. Split Hopkinson Pressure Bar, Charpy impact test, Drop tower). Split Hopkinson Pressure Bar, Charpy impact test, Drop tower) Another way to measure reaction forces can be use of piezo-electric loadcell. Calibrating against oscillation forces, impact force or against a step force All of these methods require expensive equipment and a calibrated reference sensor. This paper presents embedding of the serial manufactured piezoelectric impact load cell into OHPB (Open Hopkinson Pressure Bar) and its calibration using two pairs of strain gauges as reference sensors. Calibration of the strain gauges can be done using static loading procedure without much difficulty was demonstrated in the previous research [3]
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