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Abstract
Aiming at the determination of the rational loading waveform for rock materials, the comparative impact tests under the loadings of rectangular and half-sine stress waves were performed on red sandstone using an Ø50 mm SHPB apparatus. Experimental results with the rectangular stress wave affirm that the waveform dispersion and stress-strain curve oscillation frequently exist during the test of rock materials, which signifies that the accuracy of test results derived from the rectangular stress wave loading cannot be guaranteed. Under the loading of the half-sine stress wave, the phenomenon of wave dispersion during the tests has been eliminated radically, and there is no oscillation in the stress-strain curves. To further demonstrate the rationality of the half-sine wave loading in the SHPB test, by utilizing the three-dimensional numerical simulation approach, the propagations of rectangular, triangular, and half-sine stress waves travelling in the axial and radial directions of the SHPB with four elastic bar diameter sizes are analyzed and compared. The results show that the waveform dispersion of the rectangular and triangular stress waves always exists and will be more and more serious with increasing diameter size and propagation distance. For the half-sine stress wave, the waveform dispersion effect is very weak and not affected by the bar diameter size and propagation distance. The half-sine stress wave is the rational loading waveform for rock SHPB tests with different bar diameters.
Highlights
Rock engineering is often subjected to a lot of dynamic loads [1]. e dynamic properties of rock materials under dynamic loads are one of their essential attributes and provide the basic information for the design of underground protection works against blast and impact loadings
For the large diameter split Hopkinson pressure bar (SHPB) device, it is eager to determine a kind of loading wave that is without dispersion, oscillation, and can well achieve the stress equilibrium conditions during the test, and the halfsine stress wave has been introduced in many experimental researches [7, 15]
E main conclusions are as follows: (1) Dynamics tests of red sandstone under rectangular and half-sine stress waves were conducted by using an Ø50 mm SHPB apparatus
Summary
Rock engineering is often subjected to a lot of dynamic loads (such as blasting, impact, strike, and earthquake) [1]. e dynamic properties of rock materials under dynamic loads are one of their essential attributes and provide the basic information for the design of underground protection works against blast and impact loadings. For the large diameter SHPB device, it is eager to determine a kind of loading wave that is without dispersion, oscillation, and can well achieve the stress equilibrium conditions during the test, and the halfsine stress wave has been introduced in many experimental researches [7, 15]. Among these researches, the comparison test for the mechanics and energy characteristics of rock materials under the rectangular wave and half-sine stress wave is relatively few. For the characteristics of stress waves travelling in different waveforms, the propagations of rectangular, triangular, and half-sine stress waves in different diameter bars were compared and analyzed by using the three-dimensional numerical simulation method. e experimental and numerical results show that the half-sine stress wave is the rational loading waveform for the rock material SHPB test
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