Study On Interfacial Instability Of Strength Material

Interfacial instability is an important content in the research of natural science and engineering,and it is one of the common problems in astrophysics,geophysics,ICF and many other disciplines.Previous studies mostly aimed at the interface instability of fluids.Engineering problems gradually become clear,and the interface instability in engineering applications mostly involves the strength of medium.The development of the interface instability of strength medium is becoming one of the main problems in engineering applications.Therefore,thorough investigation of the interface instability problems for strength materials under persistent,complex loading and strong impact,is of great significance to natural science research and major projects.Firstly,according to the need of interfacial instability research,some program function is extended,based on an elastic-plastic hydrodynamics code,such as closure model in mixed cells,detonation model,adaptive mesh refinement technique,and so on.A flexible computational domain algorithm is designed to effectively improve computational efficiency.Secondly,the interfacial instability under constant and simple variable acceleration is studied.Numerical results verify the simulation codes and are consistent with the theoretical and numerical results in the literature.The instability of metal interface under constant acceleration is studied.The stability condition of the interface disturbance due to the strength of material is obtained,which is compared with the theoretical results of incompressible fluids.Thirdly,aimed at the metal interface instability under the leaning loading,a leaning loading condition is constructed to pressurize the metal slowly.The law of growth of interfacial perturbation is studied by changing the disturbance wavelength,the amplitude,the thickness of flyer and the yield strength of the material,and so on.Numerical results show that,in most cases bubble will reach stable state,and spike varies with the combination of above factors.Spike may present stable state or departing from the flyer,showing a linearly stable,nonlinearly stable or unstable state.In the steady state,maximum amplitude of spike k?max sp approximately linearly proportional to ??Vsp?2/Y and that of bubble k?max bu approximately satisfies the logarithmically proportional to ??Vbu?2/Y.Preliminary,the relationship between various physical quantities to keep interfacial stable status is obtained.Fourthly,ejection phenomenon induced by interface instability under impact is studied.The influence of the vacuum and the gaseous environment on the evolution of micro ejection is analyzed.In vacuum,the jet velocity decreases approximately linearly with the increase of the groove angle,and the difference between the V-type defects and the sinusoidal defects is small.In the gaseous environment the micro ejection undergoes four stages,such as acceleration,deceleration,deformation and breakup,atomization.In the gas environment,jet mass will be transferred from the front to the rear with the form of particles.Under different inflation pressures,the basic characteristics of each stage are similar.With the increase of the inflation pressure,the deceleration of tip speed is more rapid.Under higher inflation pressure,jump in the velocity of the jet tips may appear,due to the collision between different parts of the jet.Fifthly,based on above studies,numerical study on the instability of cylindrical metal interface is carried out,and the numerical results agree with the experimental data.Results show that the strength of materials is not negligible in metal interface instability.Inhabiting effect of yield strength is more obvious in high mode perturbation,and the influence of shear modulus is similar but less sensitivity.Most unstable mode exists in metal interface instability,decreasing with increase in the yield strength,and approximately linear with logarithm of yield strength.Perturbation grows faster,with the decrease of the thickness of the shell.