SLM NiTi记忆合金负刚度结构的能量吸收与形状恢复

Energy absorption and shape recovery of NiTi shape memory alloy negative stiffness structure fabricated by selective laser melting

采用选区激光熔化技术制备了具有不同几何参数的Ni_(50.6)Ti_(49.4)负刚度结构,分析了成形质量及相变行为,研究了几何参数及循环次数对其准静态压缩变形模式、比能量吸收及形状恢复的影响。结果表明:屈曲面几何参数对负刚度结构的变形模式、比能量吸收及形状恢复率有重要影响;非对称屈曲对负刚度结构的比能量吸收及形状恢复十分不利,通过设计合理的几何参数可以限制非对称屈曲;选区激光熔化制备的NiTi均匀负刚度结构在循环压缩后(50%应变)加热可恢复至初始高度的95%以上,且首次压缩过程中的比能量吸收可达328.3 J/kg;将不同几何参数的负刚度单元进行组合可以对整体结构的承载能力和能量吸收进行编程,实现梯度变形及吸能;此外循环次数会降低NiTi负刚度结构的承载能力和能量吸收,但对其形状恢复率几乎无影响。

Here,Ni_(50.6)Ti_(49.4) negative stiffness structures with different geometric parameters were fabricated with selective laser melting technology.Their forming mass and phase transition behavior were analyzed.Effects of geometric parameters and cycle number on their quasi-static compression deformation mode,specific energy absorption and shape recovery were studied.The results showed that geometric parameters of buckling surface have important effects on deformation mode,specific energy absorption and shape recovery rate of negative stiffness structure;asymmetric buckling is very unfavorable to specific energy absorption and shape recovery of negative stiffness structure,asymmetric buckling can be limited by designing reasonable geometric parameters;NiTi uniform negative stiffness structures fabricated with selective laser melting can recover to more than 95% of their initial height through heating after cyclic compression to reach 50% strain,and their specific energy absorption in the first compression process can reach 328.3 J/kg;by combining negative stiffness elements with different geometric parameters,load-bearing capacity and energy absorption of the overall structure can be programmed to realize gradient deformation and energy absorption;increase in cycle number can reduce load-bearing capacity and energy absorption of NiTi negative stiffness structure,but have little effect on its shape recovery rate.