Transport properties of a rectangular array of highly conducting cylinders

The method of functional equations is applied to evaluate the effective conductivity tensor for a rectangular array of highly conducting cylinders. The Rayleigh sum S ₂ is calculated by Eisenstein and Weierstrass functions. Approximate analytical formula for the effective conductivity tensor are deduced.     

环形腔中非线性周期结构介质的双稳态和光限

研究了环腔中的非线性周期结构介质的光学双稳态和光限现象，建立了输入光强与输出光强关系的表达式。理论上给出了临界入射光强低达１０＾７Ｗ／ｃｍ＾２的光学双的条件和非常有效的限光作用的条件。     

石墨拉西环制备工艺研究

本文选用胶体石墨为主要原料,采用烧结工艺制备石墨拉西环。详细探讨了粘结剂、成型工艺及热处理工艺对石墨拉西环性能的影响。结合ＳＥＭ对拉西环进行了结构分析。所制得的拉西环性能优于同类规格的进口产品。     

圆环对撞问题的理想刚塑性小变形分析及讨论

本文对对经受到撞击的圆环的刚塑性动力响应进行了小变形分析,计算结果与大变形分析作了对比。指出二者之间的差别主要是由于动力学方程不同引起的。     

坯料加热温度对H62同步齿圈精密成形工艺的影响

本文通过大量试验,现场测试,金相组织对比及理论分析,论述了在H62同步齿圈精密成形工艺中坯料的加热温度对模具的使用寿命,成形件的充满,内部质量及组织状态等方面所产生的影响,提供了最佳的坯料加热温度及其确定的依据与方法。     

The penny crack beneath the surface of a half-space: with application to the blister test

The crack tip stress intensities are found for a penny shaped crack lying beneath the free surface of a half-space, and parallel with it. This is done by employing a novel distributed dislocation approach using axi-symmetric Somigliana dislocations as the kernel of an integral equation, and provides a precise solution at the expense of little computing cost. A comparison is made with the crack tip stress intensity factors for a simple plane crack, and predictions are made for the preferred crack extension direction.     

6D μ cooling using a solenoid-dipole ring cooler for a muon collider

Six dimensional cooling of large emittance μ⁺ and μ⁻ beams is required in order to obtain the desired luminosity for a muon collider. We propose to use a ring cooler that employs both dipoles and solenoids with the additional requirement that the arcs of the ring be achromatic. We describe the lattice and the beam dynamics of the proposed ring, and demonstrate that the lattice gives substantial cooling in all 6 phase space dimensions.     

Effect of heat treatment on mechanical properties of alloy 909

Abstract

Alloy 909 is a Ni–Fe–Co alloy that exhibits a low coefficient of thermal expansion and high strength at elevated temperatures. These characteristics are suitable for demanding high temperature uses such as turbine components for aerospace and energy generation. The mechanical properties are achieved by heat treatment (solution and aging) that affects the microstructural characteristics such as grain size and precipitation of intergranular and transgranular particles. This work summarises the results of trials conducted to determine the conditions that assure the desired mechanical properties in high temperature ring rolled pieces. Results of tensile, hardness and stress rupture tests are complemented by microstructural analyses. These studies allowed for establishing a robust method for the manufacture of rings; no degradation of the product, either metallurgical or due to properties, has been reported after the method was implemented.     

Ring opening polymerization of oxetane by the use of a montmorillonite clay as catalyst

Maghnite-H⁺ was found to be an effective solid catalyst for the ring opening polymerization of oxetane. Maghnite-H⁺ is a proton exchanged montmorillonite clay. Effect of weight ratio of initiator/monomer and reaction time on the conversion of monomer and the molecular weight is investigated. Increasing maghnite-H⁺ proportion produced an increase in oxetane conversion and a decrease in Mn. A cationic mechanism for the reaction was proposed.     

Heat treating of a ring rolled Ni–Fe–Cr superalloy

Abstract

Haynes HR-120 alloy (UNS N08120) is a nickel–iron–chromium alloy that exhibits high strength at elevated temperature and resistance to carburising and sulphidising environments. These properties make this alloy suitable for the production of components of land based turbines, including rings. Manufacture and heat treating of such rings require strict control of the processing variables, such as temperature and deformation ratios, as well as the time and temperature of the solution treatment, due to their effect on microstructure and mechanical properties. It is common practice to treat this alloy at temperatures above 1100°C to promote dissolution of undesired particles and recrystallisation of deformed structures, but it has been found that grain coarsening can occur during treatment. The present work presents the results of a series of solution heat treatments that were performed within a broad range of temperatures on industrial ring rolled pieces. It was found that the increment in time and temperature enhances the dissolution of intergranular precipitates that result in the improvement of mechanical properties, but grain coarsening is observed to occur when the material is treated for long times and high temperatures. The best combination of mechanical properties and grain size was obtained by treating the material for half an hour at 1050°C.     

环形阵列微变形镜两种设计准则的分析比较

在波前校正中,环形阵列的分立式微变形镜充分利用了各个单元。环形阵列的分立式微变形镜有等单元面积和等单元宽度两种设计准则,以37单元环形阵列微变形镜为例,从校正波前适配误差和校正后剩余波前的Strehl比两方面对两种设计准则进行比较。结果表明,采用等单元面积设计的环形微变形镜校正畸变波前的性能更好。特别是波前畸变严重时,这种效果更加明显。     

Reliability indicators

This is a review paper. It describes the state-of-the-art of the research on reliability indicators for either electronic or mechanical components. Typical component failure patterns are presented and discussed. The concept of component screening using reliability indicators is then outlined. The paper sketches a theoretical approach to the problem of detecting flaws in components. The approach is based on an old concept of energy imbalance in flawed objects.     

缸套-活塞环零部件模拟磨损试验方法

随着内燃机强化技术和排放标准的提高，对缸套-活塞环配对副的耐磨性要求也更加严格，同时近年来再制造和再修复技术以及各种功能性润滑添加剂的研究，对缸套和活塞环零部件的评价方法也提出更加迫切的要求。基于磨损试验的模拟准则和试验方法，在往复式摩擦磨损试样试验机的基础上，设计了一套模拟活塞环背压的弹性膨胀加载方法，解决了缸套活塞环零部件摩擦磨损的关键技术，并制备了缸套-活塞环零部件摩擦磨损试验机。试验表明，这是一种快速、经济、准确的评价方法。     

基于环形激光陀螺调制输出的寻北系统

利用环形激光陀螺对角速度输入量具有较高灵敏度的特点,提出了一种新型的激光陀螺寻北系统,将一环形激光陀螺垂直安3 水平的恒速转台上,使输入轴与台面平行,通过测量地球自转角速度的向向分量,实现寻北过程,通过与其对称放的加速度计可以测量出由于轴系安装和系统调平引起的台面倾斜误差,从而对激光陀螺的数据出量进行补偿,同时采用单周期多位置采集技术和多周期重复测量的方法,有效地抑制了激光陀螺的测量噪声,最大限度地减少了随机误差和系统误差的影响,提出了系统的寻北精度,适合多种领域的需要。     

基于环形激光的深孔内膛形貌检测系统研究

提出了一种基于环形激光的深孔内膛检测系统,该系统主要由环形激光发生器、反射锥镜、CCD相机以及驱动装置等组成。通过对环形激光器投射在被测身管内膛上的环形光斑进行成像和分析计算,可对身管内膛的一个截面形廓进行检测,并在驱动装置的驱动下,实现对深孔内膛形貌的三维检测。