PVDF压电薄膜用于Hopkinson压杆测量泡沫金属的动态性能

首先对PVDF(polyvinylidene fluoride)压电薄膜在不同温度不同压力作用下的响应进行了系统的试验研究。然后在Hopkinson压杆系统的透射杆之间夹上PVDF压电薄膜,对其动态响应进行了检验。最后应用这个镶嵌PVDF压电薄膜的Hopkinson压杆系统,测试了泡沫铜材料在不同应变率下的应力应变关系。结果表明:(1)PVDF压电薄膜的压电常数D33是随温度和压力而变,实际应用时应对其进行标定;(2)PVDF压电薄膜可有效的用于Hopkinson压杆系统来测试低强度泡沫材料或低阻抗材料的动态响应;(3)当应变率小于0.1/s时,泡沫铜的塑性流动应力对应变率不敏感,在约400/s到5000/s应变率范围,应变小于40%下泡沫铜对应变率也不敏感。但当应变大于约20%,应变率高于400/s时,与低应变率下的值比较,塑性流动应力的应变率敏感性增加。

A Hopkinson Pressure Bar with PVDF Thin Film for Measuring Dynamic Behavior of Metallic Foams

In the present paper,first,the mechanical response of a PVDF(polyvinylidene fluoride)thin film is systematically investigated at different temperatures and different pressure forces.Then the PVDF thin film is embeded in the transmission bars of the Hopkinson pressure bar to set up a PVDF-embedded split Hopkinson pressure bar system.With this system,the dynamic response of the PVDF thin film is verified.Finally,using this system,the stress strain curves of Cu foams are measured at different strain rates.Results show that,1) the constant D_(33) of the PVDF thin film changes with temperatures and pressure forces,it must be calibrated in practical application;2) the PVDF thin film can be good for embeding in the transmission bars of the Hopkinson pressure bar to measure the dynamic behavior of foam and lower impedance materials;and 3) below 0.1/s,the palstic flow stress of Cu foams show weaker dependence of strain rates.During the range between 400/s and 5000/s,when strain is lower than 40%,the palstic flow stress of Cu foams also show weaker dependence of strain rates.But when strain is over 20% and strain rate is higher than 400/s,comparing with the palstic flow stress of lower strain rates,the dependence of strain rates of the palstic flow stress of Cu foams increases.