Several Issues Of Damage Characteristics Of Gas-filled Shperical Pressure Vessel Impacted At Hypervelocity

Pressure vessel is one of the most important components in the IADC vulnerability analysis of spacecrafts impacted by space debris.Once the pressure vessel,especially the gas-filled pressure vessel,is impacted by space debris,the venting from the perforation may cause the pressure vessel failed,but also the damage,such as cratering,may be the source of crack instability,which leads to crack disintegration and more debris is produced.It will not only threaten the safety of other components of spacecraft,but also further pollute the space environment.The dynamic behavior of gas-filled pressure vessel impacted under hypervelocity is extremely complex,which is a typical transient and nonlinear process.In particular,as a pressure structure,the front wall will produce debris cloud and stress wave propagating along the wall after perforation,and the debris cloud moving at hypervelocity in pressure gas will also produce gas shock wave.The damage behavior of the back wall or even the pressure vessel is the result of the coupling effect of the above mechanical environment factors and the membrane stress to the vessel.Compared with Whipple structure,the damage process of gas-filled pressure vessel is more complicated,and it will present diverse damage modes.Mastering the generation,movement and propagation characteristics of each secondary mechanical environment and its independent or coupling damage effect on the back wall is the premise and important problem to be solved for exploring the damage mode and mechanism of pressure vessel.The hyperveloci ty impact of space debris belongs to the extreme mechanical environment.At present,a perfect theoretical system has not been established.The ground simulation test is the most intuitive and effective means.However,for metal pressure vessels,due to th eir “non transparency”,it is difficult to directly obtain the propagation characteristics of the internal secondary mechanical environment such as debris cloud and gas shock wave.Based on the experimental measurement of secondary mechanical environmental parameters,the technical means of test,numerical simulation and theoretical analysis are used to explore the damage effect of each secondary mechanical environmental factor and master the coupling damage process of each mechanical environmental factor.The main research work is as follows:The experimental measurement of kinetic parameters for debris cloud and gas shock wave in pressure vessel is realized.Based on the ideology of separating variables,the research scheme of gas-filled pressure vessel damage effect based on test is proposed.A pressure vessel simulation device is designed and developed.The X-ray photography of the movement and evolution characteristics of debris cloud is realized through the transmission window.The experimental measurem ent of the of the debris cloud damage effect on the back wall is realized through the built-in observation board.Through the built-in PVDF piezoelectric sensor,the measurement of gas shock wave parameters and the experimental observation of its kinematic relationship with debris cloud are realized.The motion evolution and damage characteristics of debris cloud in pressure gas are obtained.A series of hypervelocity impact tests were carried out based on the pressure vessel simulation device.The debris cloud images and propagation characteristics are obtained by X-ray photography.The results show that,under the condition that the impact parameters such as the projectile velocity and the vessel wall thickness remain unchanged,the increase of the gas pressure has no effect on the initial shape and velocity of the debris cloud,but it has more effect on the attenuation of the velocity and the shape expansion.Therefore,the debris cloud damage ability to the observation plate is weakened,and the damage of the observation plate is weakened.With the increase of projectile velocity,the observation plate damage degree and range firstly increased,then decreased and then increased.Propagation characteristics and damage effect of gas shock wave.Based on the pressure vessel simulation device,the hypervelocity impact test is carried out under typical working conditions.The characteristics of gas shock wave and its time sequence relationship with debris cloud are obtained by the built-in PVDF piezoelectric sensor.On the basis of verifying the validity of the numerical simulation model,the time sequence relationship with debris cloud,gas shock wave propagation characteristics and the damage characteristics of the back wall are obtained by numerical simulation and empirical formula.The results show that,the gas shock wave is close to the debris cloud and located in the front of it,and its strength increases with the increase of gas pressure and the projectile velocity.The damage effect of the gas shock wave on the back wall is different from that of the debris cloud,which has a distinct distribution of dispersion,showing a local global continuous deformation mode.In the scope of this study,the damage mode includes large area bulging plastic deformation.Damage effect of hypervelocity impact on spherical pressure vessel.By a series of hypervelocity impact tests,the spherical pressure vessel damage characteristics are obtained,and the stress wave propagation characteristics in the vessel wall are obtained by the PVDF piezoelectric sensor.Then by numerical simulation,the influence of the parameters such as gas pressure on the front wall perforation characteristics and the stress wave propagation characteristics are analyzed.An empirical formula of the front wall perforation considering gas pressure is established.The damage process of the back wall caused by the secondary mechanical environment is analyzed and the damage effect based on the time series characteristics of the secondary mechanical environment is preliminarily obtained.The results show that the increase of gas pressure could enlarge the perforation,but because of the increase of the velocity attenuation effect to the debris cloud,the damage effect to the back wall is weakened,while the risk of tearing is increased;The stress wave propagation speed is only related to the vessel material,and its amplitude value along the propagation path of the wall presents firstly “diffusion”and then “convergence”.The time sequence characteristics of each secondary mechanical environment arriving at the back wall determine the damage process,and also affect the damage mode of the pressure vessel.Based on the comprehensive analysis of spherical gas-filled pressure vessels,it could be seen that the damage modes could be initially evaluated based on the sequential characteristics of the secondary wall arriving at the back wall.The design and development of the pressure vessel simulation device provides the experimental means for the secondary mechanical environment propagation evolution and damage effect caused by hypervelocity impact on pressure vessel.Mastering the propagation and damage characteristics of the secondary mechanical environment such as debris cloud and gas shock wave provides the theoretical basis for revealing the mechanical mechanism of the damage effect.The damage effect evaluation scheme based on the time series characteristics provides technical route reference for damage effect evaluation of gas-filled pressure vessel.The research results could provide theoretical basis and technical means for the survivability evaluation of spacecraft components after impact.At the same time,it has a certain reference value for further improving the disintegration model and the space debris environment engineering model.