Effect And Description Of Foam Materials On The Energy Absorption To UNDEX Shock

Foam materials have considerable capacity in energy absorption and mitigation of impact and blast loads. The have widely used in the anti-penetration and anti-blast protection projects. Loadings impact on the mechannical behaviors of foam material-s.Under the load of impact and air blast its mechannical behaviors have been studied systematically, while its behaviors as to UNDEX (underwater explosion) are relatively less researched. In order to enrich work on the underwater explosion, effect of foam materials on the energy absorption and description of its properties to UNDEX shock are investigated.Aluminum foam and foam glass microspheres-cement materials on the energy absorption to UNDEX are studied. The results show that they can absorb explosion energy and weaken the shock wave to UNDEX. The thickness of foam material shells impact on the shock attenuation.At the same time, the whole deforming and damage process of shells are photographed. Distribution of peak pressure versus distances are simulated by LS-DYNA, a good agreement has been achieved between the numerical simulation and experiment.In the light of the simple plane wave theory and characteristic theory, the pressur-e on the interface of steel plate and air was calculation. The characteristics of shock wave propagation in air behind steel plate were analyzed under the Brode numerical method. At the same time, experiment of underwater explosion was studied. Accord-ing to theoretical numerical method and test data, the results show that PVDF gauge to be used for measuring shock wave pressure underwater explosion was available; transverse deformation of the interior layer bottom plate was mainly contolled by the transmitting pressure via the backup plate; aluminum foams comparing to steel to be used as backup plate, deformation of the bottom plate was decreased.In order to research the mid-far field pressures of the incident shock wave on the fluid-solid interface, an experiment is designed to measure the pressure of shock wave, By means of laying two PVDF piezoelectric film sensors on the battom of double shell. The test process is simulated by the finite element method software ANSYS/LS-DYNA.The research shows that simulation results are in good agree-ment with the experimental data.PVDF sensor can be used to measure the pressure of the incident shock wave on the fluid-solid interface. The mid-far field pressures of the incident shock wave on the fluid-solid interface can be gained, it is important to evaluate the antiknock performance of ship.In the light of the compression process of aluminum foam shells under internal-explosions and mass and conservation principles, The loading process of aluminum foams could be divided into two stages:the action of the explosion load and effect of inertia; Deformed region was also divided into two areas:One was where explosion energy was transformed into kinesthetic energy and strain energy of aluminum foams, another where kinesthetic energy of aluminum foams was transformed into their strain energy, analytical calculation formulas were built for radial displacement of aluminum foams annular plates. At the same time, the relationship between particle velocity of aluminum foams and distance, and the relationship between pressure and distance were formulized in an engineering analytical calculation model.In order to test the validity of the model, experiment of underwater explosion were studied. Finally, according to comparison between analytical results and test data、numerical simulat-ion, a good agreement is obtained, the results show that model to be built is reasonable.Within the framework of hydrodynamic-elastoplastic model, the equations were established to characterize properties of aluminum foam under explosive impact. In order to solve equations, the equations were transformed into discrete and Lagrange difference forms in uniform grid. The numerical calculation method was programmed and applied to one-dimensional numerical calculation of explosion and shock response of AL foam in the water or air. A good agreement has been achieved between the numerical calculation and experiment, which shows the proposed methodologies can be effectively applied to describe the feature of AL foam under explosive impact.At the same time, the density of aluminum foams and material properties impacted on characteristics of aluminum foams.