Abstract
The constant strain rate loading and dynamic stress equilibrium are prerequisites for ensuring the experimental data of the Split Hopkinson Pressure Bar (SHPB). In order to achieve this requirement, a proper pulse shaper dimensions were used in the experiment. For this purpose, the pulse shaper diameter, thickness and strength and the strike bar length and its velocity on the incident pulse are studied by ∅80mm SHPB apparatus. Then, the parameters affecting the two key inflection points and three loading areas of the incident pulse are discussed. In addition, the improved methods for two typical non-constant strain rate waveforms for the concrete experiments are obtained based on the regular pulse shaping. Moreover, SHPB experiments are conducted for concrete by employing different pulse shaper dimensions. The results show that more valid data can be obtained by employing the pulse shaper with large thickness when the strain rate is non-constant during the experiment. The conclusions and method provide guidance for selecting pulse shaper for concrete SHPB experiments.
Highlights
Concrete and rock materials have been widely applied in the military protection field for their excellent characteristics, such as high compressive strength, low density and relatively lower cost
The incident pulse is generally trapezoidal without a pulse shaper in splitHopkinson pressure bar (SHPB) experiment
The main conclusions are as follows: (1) In the SHPB experiment, the pulse shaper can filter out the high-frequency oscillation wave and prolong the rise time of the incident pulse
Summary
Concrete and rock materials have been widely applied in the military protection field for their excellent characteristics, such as high compressive strength, low density and relatively lower cost. Based on the basic principle of SHPB (Chen et al, 2002), it is necessary to ensure the dynamic stress equilibrium and the constant strain rate to obtain valid results. Since concrete and rock behave small failure strain, the shape of the incident wave has to be adjusted to meet conditions of the dynamic stress equilibrium and the constant strain rate. Since the first and second methods have many drawbacks, such as difficulty in processing the shape of the strike bar and realizing constant strain rate loading, so the pulse shaper has become the most widely used technology. By selecting the appropriate material and size, the conditions for reducing the incident wave oscillation, achieving dynamic stress equilibrium and constant strain rate loading in the SHPB experiment can be realized
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