Li-Li Wang

The paper presents a new method to study the dynamic mechanical properties of concrete under low pressure and a high strain rate via the inversion of spherical wave propagation. The dynamic parameters of rate-dependent constitutive relation of elastic concrete are determined by measured velocity histories of spherical waves. Firstly, the particle velocity time history profiles in the low stress elastic region at the radii of 100.6 mm, 120.6 mm, 140.6 mm, 160 mm, and 180.6 mm are measured in the semi-infinite space of concrete by using the mini-explosive ball and electromagnetic velocity measurement technology. Then, based on the universal spherical wave conservation equation and the fact that the accommodation relationship in state equation satisfies linear elastic law, the inverse problem analysis of spherical waves in concrete (called “NV + T0/SW”) is proposed, which can obtain the dynamic numerical constitutive behavior of concrete in three-dimensional stress by measuring the velocity histories. The numerical constitutive relation is expressed in the form of distortion, and it is found that the distortion law has an obvious rate effect. Finally, the rate-dependent dynamic parameters in concrete are determined by the standard linear solid model. The results show that the strain rate effect of concrete cannot be ignored with the strain rate range of 10² 1/s. This study can provide a feasible method to determine the dynamic parameters of rate-dependent constitutive relation of concretes. This method has good applicability, especially in the study of the dynamic behavior of multicomponent composite materials with large-size particle filler.

Taking ship-bridge collision as an example, how the wave propagation and the dynamic behavior of materials influence the impact force and energy transformation are studied from the impact dynamics viewpoint. By using a new flexible, energy-dissipating crashworthy device developed by the authors, both the impact force and energy transformed can be markedly reduced, which is much conductive to protect both bridge and ship.

Dynamic damage evolution and its influence on the constitutive relation for materials in high strain rate are experimentally and theoretically studied. It is revealed that damage evolution is a rate-dependent process depending on both strain and strain rate, and can be modeled by the thermo-activation mechanism. For polymer PMMA, PP/PA blend and concrete, the coupled damage evolution law and the rate dependent constitutive relation (DM-ZWT model) are obtained and well supported by the experimental data.