Low strain rate compressive behavior of high porosity closed-cell aluminum foams
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摘要: 通过落锤冲击实验研究高孔隙率闭孔泡沫铝的动态压缩性能及抗低速冲击特性, 同时通过高速摄影仪观察试件的动态压缩行为, 并记录落锤冲击速度的衰减过程. 结果表明, 高孔隙率闭孔泡沫铝的抗冲击缓冲效果明显, 且在低速冲击条件下其变形特征与准静态变形类似. 采用有限元方法分析了落锤和泡沫中应力的分布特点以及表面摩擦系数对应力分布的影响. 由于摩擦力阻碍了接触面处泡沫的横向位移, 致使其压缩外形呈``鼓形''; 在低速冲击时, 应力在泡沫铝试件内部的传播周期远小于冲击的缓冲时间, 应力波现象并不明显, 应力的变化与准静态压缩时相似. 在考虑接触面上摩擦力的基础上, 通过第2类Lagrange方程建立了落锤-泡沫材料的碰撞解析模型, 将预测的落锤冲击速度的衰减过程分别与实验和有限元结果进行比较, 取得了较为一致的结论, 并进一步讨论了不同冲击速度和材料参数对冲击过程的影响.
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关键词:
- 碰撞解析模型
Abstract: Drop hammer experimental measurements are carried out tostudy the compressive behavior and energy absorption characteristics of highporosity closed-cell aluminum foam specimens subjected to low velocityimpact loading. The dynamic deformation behavior of the specimen is observedby high speed camera and the velocity attenuation of the drop hammer isrecorded. The results demonstrate that the aluminum foam has excellentenergy absorption capabilities under low velocity impact loadings, with itsdynamic compression behavior similar to that obtained under quasi-staticloading conditions. Finite element method (FEM) is employed to obtain stressdistributions in the drop hammer and foam specimen, with and without theeffects of friction on contact surface considered. The presence of frictionrestrains the transverse displacement of the contact surface, causing theobserved convex shape of the foam specimen. As the propagating period ofstresses in the specimen is far less than the attenuation duration time, thevariations of the stresses are similar to those under quasi-static loadingconditions and no obvious stress wave effect is observed. With the effectsof the friction on the contact surface accounted for, an analyticalcolliding model of the drop hammer-aluminum foam system is established. Thepredicted velocity attenuation is compared with both the experimentalmeasurements and FEM simulation results, with overall good agreementachieved. The effects of different impact velocities and mechanicalproperties of foam material on the attenuation process are discussed.-
Key words:
- analytical colliding model
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