Reaction behaviors and specific exposed crystal planes manipulation mechanism of TiC nanoparticles

Titanium carbide (TiC) nanoparticles with well-designed exposed crystal planes perform intriguing prospects for functional and engineering applications. In this study, a simple and controllable in situ synthesis strategy was proposed for the synthesis of TiC nanoparticles with specific morphology. Reaction behaviors suggested that most of TiC nanoparticles were formed by an instantaneous reaction between Al₃Ti and Al₄C₃ in the Al-rich melt and the resultant morphology was controlled by the discrepant growing rates of (100) and (111) crystal planes. In addition, a growth morphology control model was presented for the prediction and manipulation of the morphology of TiC nanoparticles by the doping of different alloying elements Me (Me = Cu, Mg, Mn, Zn, and Si). According to the morphological observations and density functional theory analyses including the interface energy, charge density differences, and orbital hybridization: Cu, Mg, and Zn atoms could stabilize the Al/TiC(111) interface, whereas Mn and Si atoms promoted the rapid growing and disappearance of the TiC(111) planes in the Al melt. This work provides a feasible way to intelligently design and manipulate TiC nanoparticles with desirable exposed crystal planes, and exhibits a promising prospect for personalized applications.     

Studies regarding simulation process to static loading of the structures obtained from polylactic acid, 3D printed

Being a relatively new process, additive manufacturing needs many studies to be able to produce parts with the required properties. The aim of the paper is to establish whether, based on the physical and mechanical properties determined by tensile testing and by applying finite element analysis (FEA), viable results can be obtained regarding the behavior of the 3D printed structures at the different, static loading. The application of FEA for the tensile testing of 3D specimens led to the results close to those obtained by the tests. The values of the results obtained by simulation are higher by up to 7.2% compared with those recorded by tests. The simulation was applied both for the printed specimens from a single material and from two materials (multi-material). Regardless of the materials used in printing and the simulation method, the results of applying FEA are close to those recorded by testing.     

Mechanical characterization and modeling stress relaxation behavior of acrylic–polyurethane-based graft-interpenetrating polymer networks

The stress relaxation behavior of acrylic–polyurethane (PU)-based graft-interpenetrating polymer networks (IPNs) was characterized via dynamic mechanical analysis (DMA) and modeled using finite element method (FEM) analysis. Stress relaxation of glassy IPN specimens was experimentally studied under flexural testing, while rubbery IPN specimens were tested in tension. The effects of varying the styrene content in the acrylic copolymer phase, compatibility of the two phases in IPNs, and changing the concentration of acrylic copolymer and PU were studied. A higher percentage of styrene content resulted in higher homogeneity of IPN specimens, and decrease in initial modulus for acrylic copolymer specimens. Additionally, glassy IPN specimens with 90% styrene shows resistance to relaxation as high as acrylic copolymer samples. Experimental results were used to develop a numerical model to study stress relaxation response of specimens. While polymer systems have been studied computationally, numerical modeling of IPN systems is still in its infancy. A three-dimensional FEM model was developed using the Generalized Maxwell model and four-term Prony series constants, which were extracted from the stress relaxation experiments. With four terms in the Prony series, a good match was observed between experimental observations and results from the FEM model.     

高电压磷酸钴锂正极材料性能调控研究

高性能、高安全储能电池的迫切需求加速了橄榄石型高电压正极材料的研究步伐。为了改善高电压磷酸钴锂(LiCoPO₄)的综合电化学性能,采用溶剂热法研究了溶剂比、过渡元素(Fe、Mn)单掺杂和双掺杂(掺杂元素总量占10%)对正极材料形貌、尺寸、反位缺陷和电化学性能的影响。结果表明,当溶剂比为2.3时,未掺杂LiCoPO₄在0.1C下表现出163.1 mAh·g^-1的最高理论比容量;双掺杂LiCo_0.9Mn_0.05Fe_0.05PO₄正极材料具有突出的循环性能,在0.5C电流密度下,循环100圈后的容量保持率为78.9%,循环稳定性得到明显改善。     

On the calibration of cohesive parameters for refractories from notch opening displacements in wedge splitting tests

Cohesive elements are commonly used to describe crack propagation in heterogeneous materials with toughening mechanisms. This work aims to provide a guideline on how these fracture parameters can be calibrated using notch opening displacements (NODs) measured via digital image correlation and force data from wedge splitting tests (WSTs). Weighted finite element model updating was applied to calibrate material and boundary condition parameters in the same framework. The influence of each parameter on force and NOD data are given together with uncertainties for the calibrated parameters. Numerical results were in very good agreement in terms of splitting force, NOD, displacement and gray level residual fields. It is shown that images obtained during WSTs focusing on the crack path (i.e., hiding the loading region) can be used to drive numerical simulations and obtain cohesive parameters.     

混合励磁磁通切换电机电磁特性分析与实验验证

混合励磁磁通切换电机通过调节励磁电流进而可以调节气隙磁场的大小,因此在电动汽车等工业控制领域有着较为广泛的应用前景。本文首先介绍12/10极HEFSM的拓扑结构,介绍了磁通切换和混合励磁的工作原理,接着利用Ansys/Maxwell软件建立电机的有限元仿真模型,对电机的磁场分布、磁链、反电势和转矩等电磁特性进行了仿真分析,研究了过饱和效应对HEFSM电磁特性的影响。结果表明:励磁电流在一定范围内对电机的电磁特性有明显的调节作用。并对电机不同工况下反电势进行测量,与有限元仿真结果进行比较,证明了电机有限元模型的正确性。     

基于响应面法的双边长初级永磁直线同步电机多目标优化设计

永磁直线同步电机由于存在边端效应以及齿槽效应,在运行中不可避免地产生推力波动。针对高速大推力密度应用场景,对一种双边长初级PMLSM开展了优化设计。将有限元法与解析法结合,首先独立分析了轴向长度、极弧系数和初级轭部高度等单个参数对电机水平推力和推力波动的影响,并进一步采用Taguchi法筛选显著性较高的结构参数。在此基础上,以提高电磁推力、减小推力波动为优化目标对电机进行响应面分析,得到最终的电机尺寸优化参数。最后制作样机并搭建实验平台,验证了所提优化方法的有效性。     

感应式球形电机结构设计与参数分析

针对目前多自由度电机结构复杂,控制难度高的问题,提出一种新型多自由度球形感应电机。该电机由三个空间对称分布的弧面定子驱动球形转子实现多自由度运行。首先,介绍了电机的基本结构和运行原理并对根据直线感应电机的设计理对电机主要参数进行计算;然后,建立Ansoft/Maxwell有限元仿真模型对电机进行稳态磁场仿真;同时对电机在不同转子参数以及不同激励时的稳态运行特性进行分析,为这类电机的优化设计与运动控制提供依据。结果表明:在额定激励下,感应式球形电机单个定子可产生1N·m的稳态转矩,稳定转速可达350r/min,满足多自由度运行要求。     

基于田口法的双余度永磁同步电机优化设计

双余度永磁同步电机有两个余度单元,具有容错率高、体积小、功率密度大等特点,在航空航天、国防、机器人等领域得到广泛应用。针对双余度电机的多目标优化设计问题,基于其典型工作模式,提出二次田口法迭代的多目标优化设计方法。首先,依据双余度度永磁同步电机的应用需求,确定优化目标参数;在初始设计参数基础上,筛选出对目标优化参数影响大的尺寸参数作为优化因子。其次,首次应用田口法筛选出双余度模式下的准最优参数;进而在单余度模式下再次应用田口法对准最优参数进行二次优化;综合两次优化结果确定最终优化参数。最后,通过有限元仿真分析对优化前后的目标参数变化进行验证分析,证明了所提出方法的有效性,也拓宽了对于该类电机的多目标优化设计思路。     

FE approach and experiments for an axisymmetric micro-yoke part forming using grain element and grain boundary element

Until present, an axisymmetric yoke part of electro-magnetic micro-speaker/receiver had manufactured by machining through the material’s removal. However, this machining process have some problems such as long production time, high precision of tool and costs. In this study, a program based on finite element method developed to establish milli-structure forming technology for micro-yoke component, one of the key parts in the multi-functioned micro-speaker/receiver. This developed program is applied for the milli-part forming in order to replace the machining process of micro-yoke. A new numerical approach is proposed to simulate intergranular milli-structure in forming the miniature yoke, in which grain elements and grain boundary elements are introduced. The results of the finite element analysis for micro-yoke part are confirmed by a series of experiments.