Analysis Of Equivalent Underwater Explosion Load And Research On Resistance Of Representative Materials

Nowadays,the maritime rights are getting more and more attention,and the protective capability of underwater structures has become one of the research emphases.Underwater explosion experiments are the most efficient method to study the anti-explosion capability of naval ship structures.However,using of explosive in underwater explosion experiments is not only dangerous,but also expensive and with long experimental period,besides,it needs hardware facilities of high requirement.The reduction of cost and difficulty in underwater explosion experiments would be very important.In order to reduce the cost and difficulty of underwater explosion experiments,on one hand,scale models could be used to experiment through similarity analysis.On the other hand,the way to obtain the equivalent underwater explosion impulsive load without explosive could be researched.In this way,equivalent underwater explosion impulsive load would be generated in a water-filled tank when a high-speed projectile impacts the water tank.The high-speed projectile is driven by high-pressure nitrogen.The equivalent underwater explosion impulsive load will be analyzed based on these two aspects in the dissertation.Then the impact resistance and damage mechanism of aluminum foam,graded aluminum foam and aluminum honeycomb are studied by the underwater shock loading experimental device,which can generate equivalent underwater explosion impulsive load by high-speed impact.Dimensional analysis,underwater shock experiment,AUTODYN simulation and ABAQUS simulation will be used in the dissertation.The main work of the dissertation is summarized as follows:The peak pressure of underwater explosion shock wave of directional warhead in scale models are studied based on dimensional analysis and AUTODYN simulation.The relationship of shock wave peak pressure between original and scale models are studied.As a result,if the mass of TNT in scale model is?~3 times of that in original,the peak pressure in original is as same as that of?times distance in the small scale.It indicate that the scale model can be used to replace the original if the similarity rule is met.For the underwater shock loading experimental device,the influence of flyer momentum on aluminum plate's deformation and pressure specific impulse are analyzed by the combination of experiment and simulation.It is found that the aluminum plate's deformation and pressure specific impulse do not change when the flyers have the same momentum value.The aluminum plate's deformation and pressure specific impulse are directly proportional to flyer momentum.The aluminum foam panels are experimented by the underwater shock loading experimental device.Two damage modes are studied at different flyer velocities by the combination of experiment and simulation.It is found that when the impact speed was low,aluminum foam panel would generate shear fracture at constrained boundary of flange.When the impact speed was high,aluminum foam panel would firstly generate fracture at the center and then generate shear fracture at constrained boundary of flange,and central fracture would generate three cracks.The influences of different density and different sequence of aluminum foam layers on dynamic response,resistance and energy absorption of graded aluminum foam panel are studied by the combination of experiment and simulation.Results indicate that if sequences of two aluminum foam layers are different,when density of back aluminum foam(the aluminum foam panel close to water)is small the deformation of graded aluminum foam panel would be slightly greater than that when density of back aluminum foam is large.But the deformation difference of the two cases is little.If average densities of graded aluminum foam panels are different,the greater the average density is,the greater the deformation of graded aluminum foam panel would be;and the greater the density of each aluminum foam layer is,the less energy it would absorb.The influence of two parameters(unit characteristic length and cell wall thickness)on the response of the aluminum honeycomb panel subjected to underwater shock load is analyzed.It is found that when the aluminum honeycomb panel has the same unit characteristic length,it will have a best cell wall thickness.The deformation of aluminum honeycomb panel with the best cell wall thickness is the minimum.In other words,the aluminum honeycomb panel with the best cell wall thickness has the strongest impact resistance.The best cell wall thickness increases when the unit characteristic length increases.Similarly,when the aluminum honeycomb panel has the same cell wall thickness,it will have a best unit characteristic length.The deformation of aluminum honeycomb panel with the best unit characteristic length is the minimum.The best unit characteristic length increases when the cell wall thickness increases.The conclusion of the dissertation has a certain guiding significance to reduce the difficulty of underwater explosion experiments.It also provides a certain basis to design the impact resistance structure of naval ship.