摘要
采用激光选区熔化(SLM)技术制备了镍钛(NiTi)合金螺旋二十四面体薄片(G-sheet)和螺旋二十四面体实体(G-solid)点阵结构,结合有限元模拟系统研究了SLM成形两种螺旋二十四面体(Gyroid)点阵结构的成形质量、相变行为和压缩性能等。研究结果表明:两种SLM成形Gyroid点阵结构的压缩曲线均呈现出三个阶段:弹性变形阶段、弹塑性变形阶段、结构逐层失效阶段。此外,两种SLM成形镍钛合金Gyroid点阵结构具有优异的能量吸收能力,G-solid点阵结构的吸收总能量低于G-sheet点阵结构。值得注意的是,在压缩过程中G-sheet和G-solid点阵结构的应力分别集中在倾斜曲面的连接处和斜杆中间位置,并且随着压缩量的增加而增大。总体而言,通过激光选区熔化技术制造的两种NiTi合金Gyroid点阵结构结合了NiTi合金和三周期极小曲面(TPMS)点阵结构的优点,展现出优异的能量吸收性能。研究结果为NiTi合金Gyroid点阵结构在能量吸收装置中的应用提供了设计思路和理论指导。
Objective The main methods of energy dissipation under impact loading are plastic deformation and fracturing of dot structures prepared from conventional metallic materials,which cannot satisfy the demands of multiple reuses and reversible energy absorption.NiTi shape memory alloy dot matrix structures prepared via selective laser melting not only have excellent mechanical and functional properties but also exhibit reversible energy absorption.When impacted,the B2-phase austenite in the NiTi alloy matrix transforms into B19'martensite,which converts mechanical energy into the internal energy of the triply periodic minimal surface(TPMS)dot matrix structure and causes energy dissipation.The aim of this study is to provide design ideas and theoretical guidance for the potential application of NiTi alloy gyroid lattice structures in energyabsorbing devices by investigating the formation quality,phase-transition behavior,and mechanical properties of different types of NiTi alloy gyroid lattice structures fabricated via laser selective melting(SLM).Methods In this study,the mathematical models of Gsheet and Gsolid lattice structures were constructed using MATLAB.Samples of these two lattice structures were successfully prepared via SLM using nearequiatomic NiTi alloy powder.Subsequently,the forming quality of the samples was systematically analyzed using scanning electron microscope(SEM),threedimensional(3D)topography,and microfocusing Xray computed tomography(microCT).Additionally,the phasetransition behavior of the samples was analyzed using Xray diffraction(XRD)and differential scanning calorimetry(DSC).The mechanical and energy absorption properties of the lattice structure samples were comprehensively evaluated by combining the obtained findings with the results of uniaxial compression test and numerical simulation using the Abaqus software.Results and Discussions The results show that the two SLMformed gyroid lattice structures possess good forming quality,high surface smoothness,and clear metal luster.The profile of the lattice structure shows clear and regular shapes,thus indicating that the internal defects of the lattice structure are well controlled during the manufacturing process(Fig.11).The two gyroid lattice structures show three different stages on the compression curve:elastic deformation,elasticplastic deformation,and structural layerbylayer failure.The compressive modulus,nominal yield strength,and ultimate yield strength of the Gsheet lattice structure are higher than those of the Gsolid lattice structure(Fig.13).This is because the bending section modulus of the Gsheet lattice structure is much smaller than that of the Gsolid lattice structure.Under the same compressive load,the internalstress coefficient of the Gsheet lattice structure is smaller than that of the Gsolid lattice structure,and the Gsheet lattice structure has a greater bearing capacity(Fig.14).Compared with the Gsheet lattice structure,the Gsolid lattice structure absorbs less total energy.During the elastic deformation stage,the energyabsorption efficiencies and unitvolume energy absorptions of the two lattice structures are similar.In the elasticplastic deformation and early layerbylayer failure stages,the energyabsorption efficiency of the Gsolid lattice structure is slightly higher than that of the Gsheet lattice structure.This is because the smaller the realtime compressive stress,the greater is the energyabsorption efficiency.When the compressive stress reaches its valley value,the energyabsorption efficiency reaches its peak value,thus indicating that the energy generated by the external stress on the sample is absorbed.The higher the degree,the greater is the energy absorbed by the gyroid lattice structure through the fracture of the support wall and support layer.The energy absorption per unit volume of the Gsheet lattice structure is much higher than that of the Gsolid lattice structure in the elasticplastic deformation and later layerbylayer failure stages.This is because compared with the Gsolid lattice structure(Fig.16),the Gsheet lattice structure has a higher elastic modulus,thus resulting in better structural stiffness and energyabsorption performance.The fracture behavior of the two lattice structures is dominated by brittleness,and ductility exists in the local areas(Fig.17).The stressdistribution cloud diagram obtained from finiteelement simulation shows that the stress of the Gsheet lattice structure is concentrated at the junction of the inclined plane,whereas that of the Gsolid lattice structure is concentrated in the middle of the inclined rod(Fig.18).Conclusions In this study,homogeneous Gsheet and Gsolid lattice structures with volume fractions of 20%were designed.The formation accuracies,phasetransformation behavior,compression performance,and stress distributions of different types of gyroid lattice structures formed via SLM were systematically investigated via experiments and simulations.The overall size of the two SLMformed gyroid lattice structures satisfies the design requirements,whereas the lattice structure has stickier powder,thus resulting in greater surface roughness.The forming quality of the overhanging section of the Gsolid lattice structure is unsatisfactory.The two SLMformed gyroid lattice structures are composed of an austenite phase(B2 phase)and a martensite phase(B19'phase),and the phase transformation behavior shows B2¬¾®¾B19'.The compression curves of the two SLMformed gyroid lattice structures show three stages:elastic deformation,elasticplastic deformation,and layerbylayer failure.The energyabsorption efficiency of the Gsolid lattice structure is higher than that of the Gsheet lattice structure in the early stages of elastic deformation,elasticplastic deformation,and structural layerbylayer failure.The energyabsorption efficiency of the Gsolid lattice structure is lower than that of the Gsheet lattice structure in the later stage of layerbylayer failure.In the elastic deformation stage,the unitvolume energyabsorption values of the two gyroid lattice structures are basically the same,whereas in the elasticplastic deformation and structural layerbylayer failure stages,the energy absorption per unit volume of the Gsheet lattice structure is much higher than that of the Gsolid lattice structure.The compressive fracture behavior of the two SLMformed gyroid lattice structures is brittle fracture.During the compression of the Gsheet lattice structure,the stress of the sample under compression load is primarily concentrated at the connection of the inclined surface,whereas during the compression of the Gsolid lattice structure,the stress of the sample under compression load is primarily concentrated in the middle of the inclined rod,and the center of the inclined rod shows a higher yield trend.
作者
李毅
王晓强
陈志桥
文世峰
史玉升
Li Yi;Wang Xiaoqiang;Chen Zhiqiao;Wen Shifeng;Shi Yusheng(School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China)
出处
《中国激光》
北大核心
2025年第8期179-191,共13页
Chinese Journal of Lasers
基金
国家重点研发计划(2023YFB4603300)
国家自然科学基金面上项目(52275332,52274400)。
