Mechanical Properties And Launch Kinetics Analysis Of Polyurethane Adapters Under Launch Conditions

The thermal launcher is simple in structure and has a single-layer closed launcher,it also has enough area between the projectiles to adapt to the tail fin and the projectile fin.The thermal launcher can be used for vehicle-mounted launch and special-shaped projectile universal launch.The gas flow is discharged along the wall of the projectile through the function of the diversion cone.In this paper,theoretical analysis,experimental verification,numerical calculation and other technical means are used to study the adaptor,which provides a scheme for the design of a thermal transmitter adaptor.The study has important engineering significance and theoretical reference.The suitable adapter material is selected according to the thermal emission environment,the surface of the adapter is sprayed with PTFE thermal protective layer.Gas flow ablation tests were carried out for various grades of polyurethane elastomer specimens and adaptor specimens with thermal protective layer,in order to compare the ablation resistance of the specimens and select the best materials.Verify the thermal protection of the PTFE layer on the adapter.Based on the hyperelastic constitutive model Mooney-Rivlin and the viscoelastic constitutive model with two relaxation times,the viscoelastic constitutive model suitable for polyurethane elastomers was established.The static/dynamic mechanical properties of polyurethane elastomer were analyzed by quasi-static uniaxial compression test and Hopkinson pressure bar(SHPB)test.Using the least square method,the viscohyper-elastic constitutive model was fitted by using the quasi-static and high strain rate test data.According to the thermal correlation coefficient of the material and the gas thermal boundary conditions,the thermal performance of the polyurethane elastomer is numerically analyzed.The results show that in a certain range,the influence of the instantaneous gas thermal boundary on the polyurethane elastomer is small,which can be ignored in the following chapters.Simp optimization algorithm was used to optimize the material distribution of the solid adapter.The irregular hollow adapter with an initial volume of 45% was obtained,and a simplified model of hollow H-column adaptor was established.Through comparing the compression performance of different internal column elements under radial load,a V-shaped internal column element with stable contact force was selected,it has no landslide and dynamic peak,the pre-bending angle was 150°.The load stability of the hollow V-column adaptor is optimized,and the arc connection belt is established,so that the force and displacement can be transmitted between the independent inner columns to avoid the instability of the structure.Finally,the hollow V-column adaptor with connection structure is obtained,it has stable compression performance(later it is still referred to as hollow V-column adaptor).The nonlinear dynamics theory is used for finite element analysis.Simplify the launch system structure,the finite element analysis model of the launch system including solid adaptor,hollow H-pillar adaptor and hollow V-pillar adaptor,the missile centroid dynamic response and the contact response between the projectile body and the adaptor were obtained by numerically calculated.The improved effect of the optimized hollow V-pillar adaptor on missile launch stability was verified.Under the action of the adapter,the missile launches from the barrel in a stable attitude,and the peak value of the contact force between the adapter and the missile is within the allowable range of engineering practice,which will not affect the surface performance of the missile and the adapter.