This article briefly overviews the research works conducted by the Wang Lili group in China, in the fields of Explosion Mechanics and Impact Dynamics.
Unlike the static cases, the mechanical responses of structures or materials under explosive/impact loadings involve stress wave propagations and dynamic deformation-failure properties of materials. This research has significant practical values in civil and defense applications, and is a research frontier in the disciplinary areas of mechanics and material science. Over more than twenty years, the group, leaded by Professor Lili Wang and actively worked by the faculty team, has been focusing its research interests in this area. The major results obtained so far include:
-
Propagating properties of loading-unloading boundary due to the elastic plastic wave velocity discontinuity across boundary. We have established a fundamental approach to study the boundary propagating behavior, and studied further the corresponding unloading failure of materials.
-
The constitutive theory of nonlinear viscoelastic material and its application: A model describing the weak-nonlinear viscoelastic properties of polymers under different strain-rates is proposed and used to analyze the propagating character of viscoelastic stress waves. Applying this wave analysis, we proposed a viscoelastic Hopkinson bar system to measure the dynamic properties of soft materials.
-
Dynamic failure due to stress wave propagations: For spallation induced by reflected unloading waves, a stress-release mechanism in the coalescence process of micro-damage is proposed, a crack-evolution equation based on a critical fragment volume is presented, and a new crack straining based spall model is established. For fragmentation of brittle materials, taking account of nucleation, growth and interaction of cracks, a new model is built, which promotes the studies on fragmentation under different strain-rates. For thermo-viscoplastic constitutive instability of materials under quasi-adiabatic impact, a macroscopic criterion for predicting the evolution of micro-adiabatic shear bands is proposed, the coupled relation between shear banding and crack extension is formulated, and the influence of geometrical factors on adiabatic shearing is revealed.
-
Engineering application based on the combining studies on stress waves and material dynamic behavior, such as bird-strike on aircrafts, ship-bridge collision and defense engineering: Based on impact dynamics analysis, a new flexible, energy-consuming crash-proof device against ship-bridge collision is developed for first time, showing that the impact force is markedly decreased, the duration under lower impact-force is prolonged, and the ship is able to turn its navigation direction and thus the device protects both ship and bridge. This new device has been applied for the bridge across Zhanjiang bay, saving more than RMB 400 millions.
Those results will be highlighted in the following parts.
|