Numerical Study On Dynamic Response Of Cylindrical Shell Structure Under Underwater Explosion

After underwater explosive explosion,in addition to the shock wave load in the initial stage,the subsequent bubble pulsation load will still have a strong impact on the dynamic response of underwater structures,especially the more sensitive equipment in the structure.Many experiments show that some properties of metal materials show sensitive rate correlation,whether the material model is reasonable and whether the parameters are correct seriously affect the accuracy of numerical simulation results.Therefore,the properties related to bubble pulsation load and material strain rate should be considered when analyzing the dynamic response of structure and equipment impact environment.Based on the relevant research data at home and abroad,the material properties of ZQ390 steel are measured by INSTRON-5500 R universal testing machine and Split Hopkinson Pressure Bar(SHPB)test device,at the same time,the dynamic constitutive model of the material is obtained.The dynamic response of floating ship under underwater explosion load is analyzed,and the influence of bubble load on structural damage is discussed.Based on the material constitutive model,the dynamic response of deep diving device under underwater explosion load is calculated,and the influencing factors of structural equipment impact environment are analyzed.The details are as follows:(1)The quasi-static test data of ZQ390 steel were obtained by INSTRON-5500 R universal testing machine,the dynamic test data of ZQ390 steel are obtained by split Hopkinson Pressure bar(SHPB),and the stress-strain curves of materials under five strain rates are obtained.It is found that ZQ390 is a ductile material under quasi-static state,and its instantaneous stress increases significantly with the increase of strain rate,which belongs to strain rate sensitive material.Through analysis,Cowper-Symonds constitutive model is adopted,and the viscosity parameter D and strain rate hardening parameter q are fitted.(2)The influence of the flow field size on the calculation accuracy in the acoustic-structure coupling method is analyzed,and the appropriate coupling interface mesh size and the gradient rate of the flow field mesh size are found.The acoustic-structure coupling method is used to simulate the dynamic response of the cylindrical shell and the bubble pulsating load under the action of underwater shock wave.The simulation,experimental and theoretical results are compared to verify the calculation accuracy of shock wave and bubble load.Taking the surface floating ship as the research object,the overall displacement,structural stress and damage form of the floating ship under only shock wave load and considering bubble load are compared,the influence of bubble load on structural damage is analyzed,and the formation mechanism of plastic hinge is deduced.(3)A simplified model of a deep diving device is established,the dynamic response of the model under underwater explosion load is calculated by acoustic-structure coupling method,and the propagation of shock wave in water is discussed.The response spectra of the cabin platform under shock wave only and bubble pulsation are compared.The results show that the bubble load will aggravate the platform response,especially in the low frequency band.The platform response of each section under different diving depth,explosive impact factor and explosive attack angle is calculated.Combined with the acceleration curve and response spectrum curve of the section plate,the influence of the change of various parameters on the impact environment of the equipment is analyzed.