Rescarch On Protective Effect Of Liquid Cabin Under Attacking By Explosion Fragments

Large warships,especially the aircraft carrier,have its prominent system of sea,air and shore attack capabilities,but also have its fatal weakness.According to characteristics of anti-ship missiles and torpedo attack,the key parts of the large warships should be given effective protection.Liquid cabin as the important part of side protection system of warships have prominent capacity on attenuation velocity of fragment.The fragments caused by anti-ship missiles have the characteristics of large number and strong penetrating power,which is extremely cared by researchers.In this paper,the protective effect of liquid cabin was researched mainly by using combination method of experiment and simulation.The main researches and results were accomplished as below.The influences of stress triaxiality and strain rate on the material fracture characteristics were investigated.The notched specimen tensile test and Split Hopkinson Tension Bar(SHTB)test were carried out.The notched specimen tensile test result was corrected by the finite element iteration method.The changing characteristics of stress triaxiality with loading time and cross section position were analyzed.The calculation method of stress triaxiality was corrected with the accumulation of strain and the spatial distribution of stress triaxiality been taken into consideration.The parameters of J-C fracture model were given based on and test and correction results.A three phased theory penetrating model of the water-backed target plate was proposed in with considering the influence of water disturbance and adiabatic shear.The residual velocity of projectile penetrating water-backed plate was deduced base on the law of conservation of energy,and the calculation results were compared with simulation results.The influence on residual velocity of water disturbance was studied by finite element simulation method(FEM).Two types of J-C material constitutive model were used in simulation researches in order to investigate the influence on calculation results of temperature softening effect.The into water velocity attenuation mechanism of high speed fragment was investigated by adopting the combination of theory and simulation method.The caliber-radius-head(CRH)was introduced to represent fragment head shape.The relationship between fragment head shape and velocity attenuation was studied by FEM.The fragment is divided into "pie" and "column" shaped fragment based on different length-diameter ratio,the speed attenuation mode of these two types fragment were studied and the critical transformation condition was given.The influences of incidence angle on fragment trajectory and velocity attenuation were studied.The speed attenuation formula of into water projectile was corrected by considering the drag resistance reduction.Based on the law of conservation of energy,the energy absorption of each penetrating stage of projectile was derived,and residual velocity of the high-speed fragment was deduced.The process of high-speed projectile penetrating liquid cabin was simulated by numerical simulation method.The speed attenuation,water pressure tank and bulkhead shape changing characteristics during the penetration were analyzed,and also investigated the influence of water level and water thickness on bulkhead damage and energy conversion.Some advice on design of liquid cabin was given based on the research results.