Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, i...Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 2.0% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of ？ to 3 under the condition in this paper when the total thickness of soft layer remains constant.展开更多
Terrorist attacks using improvised explosive devices （IED） can result in unreinforced masonry （URM） wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast e...Terrorist attacks using improvised explosive devices （IED） can result in unreinforced masonry （URM） wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM wails with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the per- formance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the perform- ance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elas- toplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.展开更多
This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed ve...This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces.Experimental data on foam-bursting capacity have been presented.Designed device can provide effective foam bursting on collapse foam.展开更多
Two numerical simulations were performed to investigate the protective effect of the foam cladding. One simulation is based on a previous experimental study, which is a ballistic pendulum with and without a foam cladd...Two numerical simulations were performed to investigate the protective effect of the foam cladding. One simulation is based on a previous experimental study, which is a ballistic pendulum with and without a foam cladding subjected to close-range blast loading. The other model is a steel beam with and without a foam cladding under blast loading. The overpressure due to the blast event can be calculated by the empirical function ConWep or by an arbitrary Lagrangian-Eulerian (ALE) coupling model. The first approach is relatively simple and widely used. The second approach can model the propagation of the blast wave in the air and the interaction between the air and the solid. It is found that the pendulum with the foam cladding always swings to a larger rotation angel compared to a bare pendulum. However, the steel beam with an appropriate foam cladding has a smaller deflection compared to the bare beam without a foam cladding. It is concluded that the protective effect of the foam cladding depends on the properties of the foam and the protected structure.展开更多
With the intermediate flow states predicted by local two phase Riemann problem,the modified ghost fluid method(MGFM)and its variant(r GFM)have been widely employed to resolve the interface condition in the simulation ...With the intermediate flow states predicted by local two phase Riemann problem,the modified ghost fluid method(MGFM)and its variant(r GFM)have been widely employed to resolve the interface condition in the simulation of compressible multi-medium flows.In this work,the drawback of the construction procedure of local two phase Riemann problem in r GFM was investigated in detail,and a refined version of the construction procedure was specially developed to make the simulation of underwater explosion bubbles more accurate and robust.Beside the refined r GFM,the fast and accurate particle level set method was also adopted to achieve a more effective and computationally efficient capture of the evolving multi-medium interfaces during the simulation.To demonstrate the improvement brought by current refinement,several typical numerical examples of underwater explosion bubbles were performed with original r GFM and refined r GFM,respectively.The results indicate that,when compared with original r GFM,numerical oscillations were effectively removed with the proposed refinement.Accordingly,with present refined treatment of interface condition,a more accurate and robust simulation of underwater explosion bubbles was accomplished in this work.展开更多
文摘Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 2.0% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of ？ to 3 under the condition in this paper when the total thickness of soft layer remains constant.
文摘Terrorist attacks using improvised explosive devices （IED） can result in unreinforced masonry （URM） wall collapse. Protecting URM wall from IED attack is very complicated. An effective solution to mitigate blast effects on URM wall is to retrofit URM wails with metallic foam sheets to absorb blast energy. However, mitigation of blast effects on metallic foam protected URM walls is currently in their infancy in the world. In this paper, numerical models are used to simulate the per- formance of aluminum foam protected URM walls subjected to blast loads. A distinctive model, in which mortar and brick units of masonry are discritized individually, is used to model the perform- ance of masonry and the contact between the masonry and steel face-sheet of aluminum foam is modelled using the interface element model. The aluminum foam is modelled by a nonlinear elas- toplastic material model. The material models for masonry, aluminum foam and interface are then coded into a finite element program LS-DYNA3D to perform the numerical calculations of response and damage of aluminum foam protected URM walls under airblast loads. Discussion is made on the effectiveness of the aluminum foam protected system for URM wall against blast loads.
文摘This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces.Experimental data on foam-bursting capacity have been presented.Designed device can provide effective foam bursting on collapse foam.
文摘Two numerical simulations were performed to investigate the protective effect of the foam cladding. One simulation is based on a previous experimental study, which is a ballistic pendulum with and without a foam cladding subjected to close-range blast loading. The other model is a steel beam with and without a foam cladding under blast loading. The overpressure due to the blast event can be calculated by the empirical function ConWep or by an arbitrary Lagrangian-Eulerian (ALE) coupling model. The first approach is relatively simple and widely used. The second approach can model the propagation of the blast wave in the air and the interaction between the air and the solid. It is found that the pendulum with the foam cladding always swings to a larger rotation angel compared to a bare pendulum. However, the steel beam with an appropriate foam cladding has a smaller deflection compared to the bare beam without a foam cladding. It is concluded that the protective effect of the foam cladding depends on the properties of the foam and the protected structure.
基金supported by the National Natural Science Foundation of China(Grant Nos.041322062 and 51075004)the Foundation of Zhejiang Educational Committee(Grant No.529003+G21144)
文摘With the intermediate flow states predicted by local two phase Riemann problem,the modified ghost fluid method(MGFM)and its variant(r GFM)have been widely employed to resolve the interface condition in the simulation of compressible multi-medium flows.In this work,the drawback of the construction procedure of local two phase Riemann problem in r GFM was investigated in detail,and a refined version of the construction procedure was specially developed to make the simulation of underwater explosion bubbles more accurate and robust.Beside the refined r GFM,the fast and accurate particle level set method was also adopted to achieve a more effective and computationally efficient capture of the evolving multi-medium interfaces during the simulation.To demonstrate the improvement brought by current refinement,several typical numerical examples of underwater explosion bubbles were performed with original r GFM and refined r GFM,respectively.The results indicate that,when compared with original r GFM,numerical oscillations were effectively removed with the proposed refinement.Accordingly,with present refined treatment of interface condition,a more accurate and robust simulation of underwater explosion bubbles was accomplished in this work.
