硬质聚氨酯泡沫塑料的应变率效应研究

Research on the Strain Rate Effect of Rigid Polyurethane Foam

利用直径37 mm口径分离式霍普金森压杆(Split Hopkinson pressure bar,SHPB)对硬质聚氨酯泡沫塑料(Rigid polyurethane foam,RPUF)开展了应变率范围为1000~2300 s^(−1)的动态压缩试验,试验结果表明RPUF材料具有明显的应变率效应。将RPUF材料视为不含应变率效应的理想弹塑性模型,并利用有限元软件ABAQUS开展RPUF材料SHPB试验的数值模拟,仿真结果表明RPUF材料的动态屈服强度随着应变率的增加而明显增大,横向惯性效应对试验结果的影响不可忽略。接着开展了RPUF材料的三轴围压(1 MPa、2 MPa、5 MPa和10 MPa)试验,试验结果表明,RPUF材料的屈服强度和静水压呈线性关系,因此研究RPUF材料应变率效应时需要考虑材料本身静水压效应对其的影响。为了获取RPUF材料的实际应变率效应,基于SHPB和三轴围压的试验数据提出一种含静水压效应和应变率效应的本构模型,并将其应用于RPUF材料的SHPB数值模拟中,该方法虽然消除了材料静水压效应对试验结果的影响,但仿真结果仍比试验值偏大,这是因为横向惯性效应对试验的影响并未在数值模拟中消除。最后通过引入横向惯性效应的修正系数对材料参数进行修正,仿真结果与试验数据一致,说明所提本构模型及修正后的材料参数能够真实反映RPUF材料本身的力学性能,从而得到RPUF材料的实际应变率效应。

The dynamic compression experiments with a strain rate ranging from 1000 s^(−1)to 2300 s^(−1)were carried out on rigid polyurethane foam(RPUF)using a split Hopkinson pressure bar(SHPB)with a diameter of 37 mm.The experimental results show that the RPUF material has obvious strain rate effect.The RPUF material is regarded as an ideal elastoplastic model without strain rate effect,and the finite element software ABAQUS is used to carry out the numerical simulation of the SHPB experiment of the RPUF material.The simulation results show that the dynamic yield stress of the RPUF material increases significantly with the increase of the strain rate.Therefore,the influence of the transverse inertia effect on the experimental results cannot be ignored.Then,the triaxial confining pressure(1 MPa,2 MPa,5 MPa and 10 MPa)tests of RPUF material were carried out.The experimental results show that the yield stress of RPUF material is linear with the hydrostatic pressure.Therefore,the hydrostatic effect of the material itself needs to be considered when studying the strain rate effect of RPUF material.In order to obtain the actual strain rate effect of RPUF material,based on the experimental data of SHPB and triaxial confining pressure,a constitutive model including hydrostatic pressure effect and strain rate effect was proposed and applied to the SHPB numerical simulation of RPUF material.Although this method eliminates the effect of material hydrostatic pressure on the experimental results,the simulation result is still larger than the experimental value.This is because the influence of the transverse inertia effect on the experiment is not eliminated in the numerical simulation.The material parameters were corrected by introducing the correction coefficient of the transverse inertia effect,and the simulation results are in good agreement with the experimental data,indicating that the proposed constitutive model and the corrected material parameters can truly reflect the mechanical properties of the RPUF material itself,thus obtaining the actual strain rate effect of RPUF material.