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Enhancement Mechanism of the Dynamic Strength of Concrete Based on the Energy Principle

by Jie Ren 1, Faning Dang 1,2,3,*, Huan Wang 1, Yi Xue 1 and Jianyin Fang 1
1
School of Civil Engineering and Architecture, Xi’an University of Technology, Xi’an 710048, China
2
State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Xi’an 710048, China
3
Shaanxi Key Laboratory of Loess Mechanics and Engineering, Xi’an University of Technology, Xi’an 710048, China
*
Author to whom correspondence should be addressed.
Materials 2018, 11(8), 1274; https://doi.org/10.3390/ma11081274
Received: 16 June 2018 / Revised: 19 July 2018 / Accepted: 20 July 2018 / Published: 24 July 2018
This paper analyzes the relationship between the rates of change of elastic strain energy, the strength during the concrete failure process, and proposes that the increased dynamic strength of concrete was caused by the hysteresis effect of energy release—according to the basic principle of energy conversion. Dynamic Brazilian disc tests were carried out on concrete specimens, with diameter of 100 mm, by using the split Hopkinson pressure bar. Test results were obtained through using a gas gun, with an impact pressure of 0.15 MPa, 0.20 MPa and 0.25 MPa, respectively. The dynamic failure process of concrete is then reproduced by numerical calculation methods. Finally, the energy characteristics during the concrete failure process at different strain rates are studied, and the enhancement mechanism of the dynamic strength of concrete is verified. The results showed that the dynamic tensile strength of concrete increased by 9.79% when the strain rate increased by 61% from 60.25 s−1; and when the strain rate increased by 92.8% from 60.25 s−1, the dynamic tensile strength of the concrete rose by 46.28%. The rates of change of both input energy and dissipated energy meet at the peak stress of the material. The increases in rates of change for the two kinds of energy were not synchronized, so excess input energy could be stored as concrete strength increased. As a result, the extra energy stored after peak stress led to a higher degree of concrete fragmentation and greater kinetic energy of the fragment. These results offer research directions for improving the dynamic strength of concrete. View Full-Text
Keywords: concrete; dynamic strength; energy conversion; dynamic Brazilian disc test; split Hopkinson pressure bar concrete; dynamic strength; energy conversion; dynamic Brazilian disc test; split Hopkinson pressure bar
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Ren, J.; Dang, F.; Wang, H.; Xue, Y.; Fang, J. Enhancement Mechanism of the Dynamic Strength of Concrete Based on the Energy Principle. Materials 2018, 11, 1274.

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