Structural Stability And Dynamic Reliability Research Of Underwater Supercavity Vehicle

Because the structure of supercavity vehicle generally has to be designed as slenderconfiguration, and the high longitudinal force and the tail impact force are both very likely tolead to the structure of supercavity vehicle in damage. A large number of theory analysis andexperimental research have been made on structural vibration characteristics of supercavityvehicle, and people had made some important research results. However, these studies did nottake into account the randomness of physical and geometrical parameters of structure. But inactual operation process, because the randomness of the material properties, as well as thestructure of supercavity vehicle may subject to the effect of various random factors in themanufacture, installation processes, they are all produce certain effect on dynamiccharacteristics of structure.So it is necessary to research dynamic stability and reliability onthe structure of supercavity vehicle with stochastic parameters. The major content of thethesis as follows:1. The equilibrium equation when supercavity vehicle in the steady-state motion and inthe partial cavitaion regime were established, and the relations for the balanced forces on thecavitator and the tail were obtained, The balanced values of the angles are founded by theiteration process, At last we analysis the changing regularity of the two cavity models bycomparing the two basic form models under the conditions of the different parameters.According to the hydrodynamic characteristic when the supercavity vehicle enters into water,we can infer the calculating formula of the unsteady cavity configuration.2. Taking aim at the problems of dynamic stability when the head of supercavitatingprojectile subject to the axial random load at high speed motion underwater, the dynamicpartial differential equation of supercavitating projectile structure was established, then thenumerical calculation for the dynamic stability of supercavitating structure was performedwith Bolotin method.3. In consideration of the stochastic parameters, the regions of dynamic instability ofprojectile with stochastic parameters were constructed based on the random factor method,the mean value and the variance of the boundary of dynamic instable regions were thenderived by using the random variable’s algebra synthesis method. The influence of stochasticparameters on the dynamic instability of supercavitating projectile was also analyzed. The computational results indicated that the stochastic parameters have certain influence on thedynamic instability. The results provided a certain theoretical foundation for the design ofsupercavitating projectile.4. Dynamic reliability of stochastic parameters supercavitating torpedo under the randomexcitation is investigated. The supercavitating torpedo is modeled by using eight-nodesuper-parametric shell elements. The impact loads and planing forces of the tail onsupercavitating torpedo structures are simplified into two stationary random processes with acertain phase difference, and considering the correlation between the impact loads and planingforces of the tail on supercavitating torpedo structures, the random excitations are transformedinto sinusoidal ones in terms of the pseudo excitation method.5. The structural stress response can be obtained through combining Newmark methodwith pseudo excitation perturbation method, and then all required digital features for dynamicreliability of supercavitating torpedo have be calculated. The expressions of the mean valueand the variance of stochastic supercavitating torpedo dynamic reliability are educed from thefist excursion probability mechanism of calculating dynamic reliability, the structure dynamicreliability problems of supercavitating torpedo with random parameter have be solved. Finally,the method of this paper was proved feasible and available comparing with the Monte Carlomethod by an example.