Construction Of Constitutive Model And Numerical Simulation Of Cushioning Process Of EPE

With the development of computer technology,more and more packaging designers use finite element simulation technology to study the cushioning performance of cushioning packaging materials and optimize the cushioning packaging design.The accuracy of mechanical performance parameters of cushioning packaging materials has an important influence on the simulation results.In order to ensure the accuracy of the simulation results,it is necessary to study the mechanical properties of cushioning packaging materials and construct a perfect constitutive model to obtain accurate material parameters.In this paper,cushioning packaging material polyethylene foam(EPE)as the research object,mainly from the following four aspects:(1)The mechanical characteristics of EPE under quasi-static compression,dynamic impact and tensile load were studied through experiments.The effects of density,strain rate and temperature changes on the compressive stress-strain curves under compression and impact,and the effects of density and strain rate changes on the tensile stress-strain curves were discussed respectively.(2)Based on the experimental data of EPE under static compression and dynamic impact,the density term of density and strain coupling is constructed on the basis of the Sherwood-Frost phenomenological constitutive model framework.Based on Johnson-Cook temperature softening term,the temperature term coupling temperature and strain is constructed.On the basis of Nagy model and thermally activated Seeger model,the strain rate term of strain rate and strain coupling is constructed,and the complete compression impact constitutive model of EPE is established by combining the density term and temperature term.Based on the constructed constitutive model and Low Density Foam model in ABAQUS,the drop hammer impact test was simulated.The peak acceleration error between the simulation results and the experimental results was within 5 g,which verified the accuracy of the EPE constitutive model and the simulation model.(3)The time-acceleration curves and peak acceleration-static stress curves of EPE with different densities(15 kg/m~3,21 kg/m~3,28 kg/m~3,36 kg/m~3)at different drop heights(460 mm,660 mm,760 mm,970 mm)and different ambient temperatures(0°C,20°C,40°C,60°C)were obtained by finite element simulation.The influence of density and temperature changes on the dynamic cushioning curves of EPE at different drop heights was studied,and the influence law was consistent with the results obtained by the existing experimental methods.The simulation method and results can provide technical means and reference for cushioning packaging design.(4)Based on the tensile experimental data of EPE,the tensile constitutive models of density and strain coupling and strain rate,strain and density coupling are constructed.Combined with the tensile constitutive model and finite element simulation technology,the uniaxial tensile process of EPE was simulated,and the accuracy of the tensile constitutive model was verified.Finally,the cushioning process of EPE cushioning pad when it falls on the corner and surface is simulated,and the situation of cushioning pad under tensile load during the cushioning process is revealed.The results show that the compression and tensile mechanical properties of foam materials need to be comprehensively considered when the cushioning characteristics of EPE cushioning pad are analyzed by finite element simulation.