低应变速率下形状记忆合金的特性实验研究

形状记忆合金以其特有的形状记忆效应和超弹性,被广泛应用于医学、航空和建筑防震。在耗能性机构中,需要形状记忆合金能够在变速率条件下工作。为了获得非静态条件下的行为特性,比较静态和非静态条件下形状记忆合金的行为特性的差异,本文采用一种新的分析方法,即以形状记忆合金的特性参数为对象,来分析不同应变速率对形状记忆合金特性的影响。在不同的应变速率(0.0005/s,0.001/s,0.005/s,0.01/s,0.05/s,0.1/s)下,对50.8at%-Ni-Ti记忆合金丝的形状记忆效应和超弹性特性进行了实验研究。在低应变速率范围内,由实验结果得到:随应变速率增大,两种特性行为中的各纯相的杨氏模量保持不变;拉伸过程相变起始和终了临界应力会增大,卸载过程相变起始和终了临界应力会减小,滞后环面积增大;相变硬化系数在形状记忆效应行为中会增大,而在超弹性行为中基本不变。

Experiment Research of Shape Memory Alloy with Low Strain Rates

Shape memory alloy(SMA) has been applied widely in medicine,aerospace and architecture vibration due to its unique shape memory effect(SME) and super-elasticity(SE).In dissipation device it is often required to operate at different strain rates.In order to obtain its non-static behavior properties and to compare the difference between static and non-static conditions,a new kind of analysis method which chooses characteristic parameters based on shape memory effect and super-elasticity was adapted to analysis the effect of different strain rates on SMA characteristic.Then uniaxial loading and unloading experiments are carried out at strain rates 0.0005 /s,0.001 /s,0.005 /s,0.01 /s,0.05 /s and 0.1 /s under constant temperature.Within these strain rates the following results are obtained.With strain rate increasing Yang module of every pure phase in the SME and SE always keeps constant,the start and finish critical stresses increase during loading and decrease during unloading,furthermore the area of hysteresis loop increases,the value of transformation coefficient probably increases in SME,and almost keeps invariability in SE.