周铣加工表面形貌仿真新算法

考虑主轴偏心，基于周铣过程中刀具切削刃上任意点与工件相对运动的轨迹方程和周铣过程几何特征，构造出可以求解周铣加工表面上任意一点形貌高度值的三维表面形貌仿真算法，并给出了相应的仿真算例。该算法无需对刀齿进行微段离散，并且不依赖于工件网格划分，加工表面上任意一点形貌高度值的计算次数等于刀具齿数，具有通用性好、运算速度快、结果准确度高的特点。     

Experimental study on RC beams with FRP strips bonded with rubber modified resins

This paper presents the effects of adhesive properties on structural performance of reinforced concrete (RC) beams strengthened with carbon fiber reinforced plastic (CFRP) strips. The epoxy adhesives modified with liquid rubber of different content were used to bond the CFRP strips, and four point bending experiments were carried out on RC beams. The experimental results show that different CFRP strip thickness of 0.22 and 0.44 mm resulted in a transition of failure mechanism from interfacial debonding along the CFRP-concrete interface to concrete cover separation starting from the end of CFRP strips in the concrete. Moreover, it is suggested that no matter interfacial debonding or concrete cover separation, the rubber modifier enhanced the structural performance by increasing the maximum load-carrying capacity and the corresponding ductility, compared with the beams bonded with a neat epoxy resin. The improvement of structural performance due to modified adhesive was associated with the modification of stress profiles along the CFRP-concrete interface especially the stress concentration at the end of FRP, and the enhanced interlaminar fracture toughness. Rubber modified epoxy therefore is worth further studying in practical repair applications.     

Magnetoelectric coupling in ferroelectromagnets with antiferroelectric and antiferromagnetic orders

This paper reports a theoretical prediction of magnetoelectric-coupling-induced ferromagnetic ordering behavior in ferroelectromagnets with antiferroelectrically and antiferromagnetically ordered components. A Monte-Carlo algorithm based on Janssen model with an intrinsic magnetoelectric coupling between electric polarization and Ising spin is developed. A mean-field approach based on the Heisenberg model is proposed. The simulation reveals that both weak ferromagnetic order and weak ferroelectric order below certain temperature can be activated by the magnetoelectric coupling and by applying external electrical field. The mean-field approach confirms the weak-ferromagnetic phase transitions revealed by the simulation.     

万向联轴器法兰叉架的法兰强度计算及厚度确定

分析了万向联轴器法兰叉架的法兰破坏的原因 ,对法兰不同轴向截面进行受力分析 ,提出法兰厚度的计算公式。用这个计算公式可以对承担任何公称扭矩的任何轴向截面的法兰叉架的法兰进行强度计算及厚度确定。     

Investigation of Optimal Megnetic Properties in NdFeB Magnets by Artificial Neural Network

In order to study the effect of alloy component on magnetic properties of NdFeB magnets, the experiment schemes are carried out by the uniform design theory, and the relationship between the component and the magnetic properties is established by artificial neural network(ANN) predicting model.The element contents of alloys are optimized by the ANN model.Meanwhile, the influences of mono-factor or multi-factor interaction on alloy magnetic properties are respectively discussed according to the curves ploted by ANN model.Simulation result shows that the predicted and measured results are in good agreement.The relative error is every low, the error is not more than 1.68% for remanence Br, 1.56% for maximal energy product (BH)m, and 7.73% for coercivity Hcj.Hcj can be obviously improved and Br can be reduced by increasing Nd or Zr content.Co and B have advantageous effects on increasing Br and disadvantageous effects on increasing Hcj.Influence of alloying elements on Hcj and Br are inverse, and the interaction among the alloying elements play an important role in the magnetic properties of NdFeB magnets.The ANN prediction model presents a new approach to investigate the nonlinear relationship between the component and the magnetic properties of NdFeB alloys.     

Effect of Rare Earth Element Ce on Microstructure and Properties of Aluminum Rod for Electrical Purpose

The effect of rare earth element Ce on microstructure, electrical conductivity and mechanical properties was studied.Using optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffractometer, the microstructure and phase composition of aluminum rod for electrical purpose were measured and analyzed.The results indicate that rare earth element Ce can considerably refine grain size of aluminum rod for electrical purpose,improve the regular distribution pattern of the impurity, such as silicon and iron which present in the aluminum matrix,form stable metal compound with pernicious impurity.This metal compound precipitates on the crystal boundary.As a result, the solid solubility of impurity in aluminum reduce, and the electrical conductivity of aluminum rod for electrical purpose is improved.It is found that the mechanical properties of aluminum rod for electrical purpose are improved by rare earth element in certain range of RE addition.     

Electrical Properties and Electroluminescence of 4H-SiC p-n Junction Diodes

Homoepitaxial growth of 4H-SiC on off-oriented Si-face(0001 ) substrates was performed by using the step-controlled epitaxy technique in a newly developed low-pressure hot-wall CVD (LP-HWCVD) system with a horizontal aircooled quartz tube at around 1500 ℃and 1.33 × 104 Pa by employing SiH4 C2H4 H2. In-situ doping during growth was carried out by adding NH3 gas into the precursor gases. It was shown that the maximum Hall mobility of the undoped 4H-SiC epilayers at room temperature is about 430 cm2 ·V -1 ·s -1 with a carrier concentration of ～ 1016 cm-3 and the highest carrier concentration of the N-doped 4H-SiC epilayer obtained at NH3 flow rate of 3 sccm is about 2.7 × 1021 cm-3 with a mobility of 0.75 cm2 ·V -1 ·S -1. SiC p-n junctions were obtained by epitaxially growing N-doped 4H-SiC epilayers on Aldoped 4H-SiC substrates. The C-V characteristics of the diodes were linear in the 1/C3-V coordinates indicating that the obtained p-n junctions were graded with a built-in voltage of 2.7 eV. The room temperature electroluminescence spectra of 4H-SiC p-n junctions are studied as a function of forward current. The D-A pair recombination due to nitrogen donors and the unintentional, deep boron center is dominant at low forward bias, while the D-A pair recombination due to nitrogen donors and aluminum acceptors are dominant at higher forward biases. The p-n junctions could operate at temperature of up to 400 ℃, which provides a potential for high-temperature applications.     

线接触热弹流润滑的数值分析

基于Ree—Eyring流变模型，建立线接触热弹流润滑方程，通过数值计算得出了载荷参数、速度参数、材料参数和滑滚比对于二次压力峰、最小油膜厚度和最大油膜温度的重要影响。     

新一代顺序式X射线荧光光谱仪——飞利浦PW2400型X射线荧光光谱仪

介绍了飞利浦ＰＷ２４００型新的Ｘ射线荧光光谱仪，它采用了多种新技术，包括脱Ｘ射线管（ＳＳＴ），直读光学定位传感器（ＤＯＰＳ）多道分析器（ＭＣＡ）及新的窗式软件。