Study On Cushioning Energy Absorption Characteristics And Constitutive Relationship Of Rigid Polyurethane Foams

In order to ensure the projectile enters the water quickly and safely and to lower the maximum impact load generated at the time of entry.In this study,the methods of experiment,theory,and numerical simulation were utilized to examine the load characteristics of rigid polyurethane foam(RPUF),which was used as the cushion head material of the missile body in the high-speed water entry process.primarily focusing on the following elements:Firstly,an electronic universal material testing machine and a Hopkinson rod compression device were used in the study’s initial uniaxial compression tests to acquire the stress-strain curves of RPUF with various densities under various strain rates.This led to extensive research into the static and dynamic behavior of RPUF.High-speed cameras and SEM scanning electron microscope were used to view and study the specifics and failure mechanisms of the compression deformation process of RPUF.Secondly,by examining the stress-strain curve of the RPUF at high strain rates,this work revealed the buffering energy absorption process and parameter fluctuation of RPUF.Based on this,this article investigates the energy absorption properties of RPUF buffering from two perspectives: energy absorption capacity and capacity absorption efficiency,and compares them with the energy absorption properties under quasi-static conditions to offer recommendations for the design and application of buffering.Then,based on the quasi-static/dynamic compression experimental results,a macroscopic intrinsic model of RPUF is built in this study.The good agreement between the experimental curves and the fitted results shows that this model is capable of capturing the compression deformation behavior of RPUF.Error analysis was utilized to confirm the model’s plausibility before it was applied to the subsequent numerical simulation calculations.Lastly,LS-DYNA was used to perform the numerical simulation of the fluid-solid coupling between the entry of light bullets into the water and the entry of the bullet body with the head cap,and to study the influence of different entry velocities,buffer thickness,and buffer density on the buffer performance of the head cap.This verified that the buffer head cap has a good load reduction effect under the conditions.