Analysis Of Local Non-linearity Of Bundled Connection Structure And Its Influence On Launch Vehicle Dynamic Behaviour

As the key force-transmitting component between the core booster and booster of the strap-on launch vehicle,the mechanical characteristics of the bundled connection structure affect the dynamic behavior of the strap-on launch vehicle,and then affect the safety and reliability of the launching.The inherent clearance,friction,contact and pre-tightening force of the bundled connection structure make it obvious local non-linearity mechanical characteristics.It is of great significance to develop the local non-linearity of the bundled connection structure and its influence on the dynamic behaviour of strap-on launch vehicle.Taking a new type of strap-on launch vehicle as the research object,this paper is foucus on the analysis of the non-linear mechanical characteristics of the bundled connection structure,simplified modeling and model parameter identification,rocket dynamic modeling considering the local non-linearity of the bundled connection structure,and the impact analysis of the local non-linearity of the bundled connection structure on the launch vehicle dynamic behavior.The main research contents are summarized as follows:(1)Based on two typical bundled connection structures,the static and dynamic mechanical research is researched by two finite element models,the nonlinear mechanical characteristics of the two bundled connection structures are obtained accurately;The effects of the pre-tightening force of explosive bolts,the radius of explosive bolts and the thickness of separator on the mechanical characteristics of the bundled connection rod are studied,Which laid the foundation for accurate simulation of the bundled connection structure and more accurate dynamic analysis of the strap-on launch vehicle.(2)A simplified mechanism model of the bundled connection rod is proposed,the force-state mapping surface of the bundled connection rod is constructed according to the force-state mapping method,so as to identify the parameters of the simplified mechanism model of the bundled connecting rod;By comparing the dynamic response of the finite element model and the simplified parameter model of the bundled connection rod,the reliability of the parameter identification results is verified.(3)Taking the general form of strap-on launch vehicle as the research object,the small deviation attitude dynamic equation of launch vehicle considering rigid body motion,elastic vibration of rocket,liquid sloshing of tank and local non-linearity of bundled connection structure is established;The elastic vibration equation of launch vehicle is solved based on pseudo-force method,and the solving algorithm of dynamic equation group considering local non-linearity of bundled connection structure is introduced;The influence of the local nonlinearity of the bundled connection structure on the attitude motion of the launch vehicle is analyzed.(4)Based on the Timoshenko beam theory,the finite element model of the strap-on launch vehicle considering the local non-linearity of the bundled connection structure is established,the influence of the local non-linearity of the bundled connection structure on the dynamic characteristics of the launch vehicle during the launching stage is analyzed;The loading situation of the first three seconds of the launch vehicle is simulated,the influence of the local non-linearity of the bundled connection structure on the dynamic response of the launch vehicle is analyzed.The research results in this paper have important engineering value for accurately predicting the dynamic characteristics and response of the strap-on launch vehicle,improving the attitude control accuracy and reliability,and ensuring the safe and reliable launch of the launch vehicle.