基于拓扑优化的多复合材料3D打印增强方法及实验研究

针对多复合材料3D打印制造中利用连续纤维增强模型强度问题,提出利用拓扑优化技术对模型进行增强的方法,提升其力学性能。基于变密度法中的固体各向同向材料惩罚(Solid Isotropic Material with Penalization,SIMP)方法,引入体积分数常量,求解出模型的拓扑结构;建立采用增强材料填充拓扑结构、基础材料填充空洞结构的多复合材料3D打印材料分布模型,从而使得模型的整体结构得到强化。为验证该方法的可行性,以120 mm×80 mm×10 mm的矩形小板为例,利用ANSYS软件建立静力学仿真模型,与未增强模型力学分析结果进行对比,得到采用层间增强、轮廓增强和拓扑增强的模型在Y方向上的位移降低幅度分别为88.90%、87.10%和94.13%,采用拓扑增强的模型位移降低幅度最大;拓扑增强相对于轮廓增强和层间增强在Y方向位移上分别降低了50.79%和54.65%,表明该方法适用于多复合材料3D打印。根据仿真内容进行静力学实验分析,实验结果表明优化结构对比未优化结构在位移上减小了39.6%,证明了该方法对于复合材料3D增强打印具有实用价值。

产品服务系统理论和关键技术探讨

针对当前制造企业正在向服务业拓展,产品服务系统作为一种新的制造系统模式正在迅速发展的态势,从用户对服务的需求、企业通过服务促进产品创新、企业差异化竞争的需要、企业争取客户的需要、环境保护的需求,以及信息及网络技术对产品服务的推动作用等角度分析了其背景.综述了产品服务系统相关研究和实践的发展,分析了各种产品服务的特点和产品服务系统理论,以及产品服务系统的共性的关键技术,主要包括:产品服务全生命周期管理理论和方法、产品服务系统的组织和过程优化理论;面向产品服务的设计技术、面向产品服务的用户需求挖掘技术、产品维修服务技术、产品服务信息采集技术、产品服务的人性化技术等.综述了一些产品服务系统的功能和特点.

Cutting Characteristics of CFRP Boards Using Electroplated Diamond Wire Tools

CFRP （carbon fiber reinforced plastic）, which is composed of carbon fibers in a resin matrix, is an extremely strong and light composite material that has found use in the aerospace and automotive industries. CFRP boards are very difficult to machine using common machining processes. Various machining artifacts, such as burrs and delamination, occur frequently when machining CFRP. Adequate techniques for machining CFRP have not yet been established. Recently, electroplated diamond wire machining technology has found use in cutting hard, brittle materials such as silicon and sapphire. In this study, we used an electroplated diamond wire saw to cut a CFRP workpiece. We quantified the cutting forces imposed on the workpiece and observed the surface state of the workpiece after cutting. We demonstrated that an electroplated diamond wire tool is suitable for the high-quality machining of CFRP boards.

Tailored microstructures and strengthening mechanisms in an additively manufactured dualphase high-entropy alloy via selective laser melting

Dual-phase high-entropy alloys(DP-HEAs)with excellent strength-ductility combinations have attracted scientific interests.In the present study,the microstructures of AlCrCuFeNi3.0DP-HEA fabricated via selective laser melting(SLM)are rationally adjusted and controlled.The mechanisms engendering the hierarchical microstructures are revealed.It is found that the AlCrCuFeNi3.0fabricated by SLM at the scanning speed of 400 mm s-1falls into the eutectic coupled zone,and increasing the scanning speed will make this composition deviate away from the eutectic coupled zone due to the increased cooling rate.The enrichment of Cr and Fe solutes with large growth restriction values ahead of the solid/liquid interface can develop a constitutional supercooling zone,thus facilitating the heterogeneous nucleation and nearequiaxed grain formation.The synergy of the near-eutectic DP nano-structures and near-equiaxed grains instead of columnar ones effectively suppresses cracking for the as-built DP-HEA.During the tensile deformation,the intergranular back stress hardening similar to the grain-boundary strengthening is discovered.Meanwhile,the near-eutectic microstructures comprised of soft face-centered cubic and hard ordered bodycentered cubic(B2)DP nano-structures lead to plastic strain incompatibility within grains,thus producing the intragranular back stress.The Cr-rich nano-precipitates inside the B2 phase are found to be sheared by dislocation gliding and can complement the back stress.Additionally,multiple strengthening mechanisms are physically evaluated,and the back stress strengthening contributes obviously to the high performances of the as-built DP-HEA.

Flexible high-performance microcapacitors enabled by all-printed two-dimensional nanosheets

Chemically exfoliated nanosheets have exhibited great potential for applications in various electronic devices.Solution-based processing strategies such as inkjet printing provide a low-cost,environmentally friendly,and scalable route for the fabrication of flexible devices based on functional inks of twodimensional nanosheets.In this study,chemically exfoliated high-k perovskite nanosheets(i.e.,Ca_(2)Nb_(3)O_(10)and Ca_(2)NaNb_(4)O_(13))are well dispersed in appropriate solvents to prepare printable inks,and then,a series of microcapacitors with Ag and graphene electrodes are printed.The resulting microcapacitors,Ag/Ca_(2)Nb_(3)O_(10)/Ag,graphene/Ca_(2)Nb_(3)O_(10)/graphene,and graphene/Ca_(2)NaNb_(4)O_(13)/graphene,demonstrate high capacitance densities of 20,80,and 150 nF/cm^(2) and high dielectric constants of 26,110.and 200,respectively.Such dielectric enhancement in the microcapacitors with graphene electrodes is possibly attributed to the dielectric/graphene interface.In addition,these microcapacitors also exhibit good insulating performance with a moderate electrical breakdown strength of approximately 1 MV/cm,excellent flexibility,and thermal stability up to 200℃.This work demonstrates the potential of high-k perovskite nanosheets for additive manufacturing of flexible high-performance dielectric capacitors.