基于选择性激光熔化的钛合金点阵结构等强度设计及工艺参数耦合优化

Aiming at the urgent demand of high ratio strength/stiffness components and equipment in aviation and aerospace fields, this project conducts equip-intensity design and processing parameters optimization on Ti6Al4V lattice structures fabricated using selective laser melting (SLM) in order to tackle the challenge in designing SLM-fabricated lattice structures due to a lack of the“design for additive manufacturing (DfAM)”method. By utilizing theoretical analysis, numerical simulation and experimental study, the key factors which affects the processing quality of the lattice structures are determined and the numerical relationship among geometric parameters of the structures, microstructures of the material and the performance of the lattices is established. The numerical relationship will be also used to establish the optimization method on geometrical parameters of the structures, as well as to conduct compensation modelling in order to design isotropic specimens under the rapid heating and cooling condition. Moreover, the coupling effect of the key processing parameters on the processing quality of the lattice structures will be revealed and thereafter the parameters, which will be customized to fabricated different lattice structures, will be optimized. The proposed design method will be used to fabricate an aviation/aerospace component, which will be tested in real service condition. In total, a full set of equip-intensity design method and optimization method on processing parameters of Ti6Al4V lattice structures will be proposed after the project is completed, which will facilitate the rapid development of the AM technology on fabricating key components used in aviation and aerospace equipment.

本项目面向通用航空航天装备及零部件进一步提升比强度、比刚度的迫切需求，针对缺乏面向增材制造的金属点阵结构等强度设计方法的现状，以基于选择性激光熔化（SLM）的Ti6Al4V钛合金点阵结构为研究对象，结合理论分析、数值模拟和实验研究等手段，分析几何参数和工艺参数两类影响点阵结构力学性能的关键因素，研究高速升温—冷却工况下点阵结构几何参数—材料组织生长—结构宏观性能之间的映射关系，建立面向材料组织均匀性约束的点阵结构几何优化和等强度补偿方法，揭示制约点阵结构高质量成形的关键工艺参数及其耦合作用原理，实现钛合金点阵结构高质量成形的SLM工艺定制，完成基于点阵结构填充的航空航天零件的轻量化设计和应用考核，形成一整套基于SLM技术的钛合金点阵结构等强度设计理论和高质量成形工艺优化方法，促进我国航空航天关键零部件增材制造技术的快速发展。

本项目针对通用航空航天零部件进一步提升比强度、比刚度存在的问题，针对缺乏面向增材制造工艺特性的金属点阵结构等强度设计方法的现状，以选择性激光熔化（SLM）成形的钛合金点阵结构为研究对象，基于相场模拟研究SLM工况下点阵结构成形缺损产生与演变机制，实现面向增材制造工艺特性的钛合金点阵结构的等强度设计，分析影响点阵结构力学性能的关键工艺参数，实现典型钛合金点阵结构的高质量成形，完成基于点阵结构填充的典型航空航天结构样件试验。主要结论如下：.① 建立了基于相场方法的二维熔池动力学模型，揭示不同线性能量密度下成形过程中缺陷产生及演变机制。利用重熔、调整工艺参数的方法消除了孔隙和飞溅现象，为点阵结构等强度设计提供了参考。.② 研究了SLM工艺参数对点阵结构样件的致密度、尺寸精度、顶面形貌以及粘粉现象的影响机制，选择桁架结构和空间极小曲面结构两类点阵结构为对象，设计并加工得到点阵样件，完成了准静态压缩性能测试及其变形特性分析。.③ 以翼结构为典型案例，以减重优化为目标，将重构模型设计为外壳+内填充多孔结构，将内填充多孔结构所占据的空间定义为设计域，并根据原模型应力分布特性划分设计域，且每个设计域内的多孔结构承受的不同的应力极限，得到基于梯度空间极小曲面结构单元的梯度点阵结构填充样件模型，后续测试结果表明该样件的工艺性能满足设计要求。