冷却液及粒度对电镀CBN砂轮端面磨削的影响

实验研究了电镀小直径ＣＢＮ砂轮端面磨削沟槽底面时磨粒粒度、冷却液供给方式对磨削效果的影响。砂轮磨粒尺寸较小时,在砂轮作业面上容易发生切屑粘结和电镀镀粒层剥离等异常损伤;选取较大尺寸的磨粒可以实现砂轮的正常磨削,采用轴心普通冷却液供给和外部高压冷却液供给并用的冷却液供给方法有较长的砂轮寿命,得到的已加工表面粗糙度在Ｒｚ４μｍ以下。     

Molecular-dynamics-based cohesive zone law for brittle interfacial fracture under mixed loading conditions: Effects of elastic constant mismatch

One approach for performing a finite-element simulation of interfacial fracture is to use a cohesive zone model. The cohesive zone model defines the interfacial traction–separation relation. Experimental determination of such a relation has been difficult. Most previous work has been confined to tensile loading, and much less has been devoted to mixed-mode loading conditions. Even so, specific laws are often assumed rather than predicted. Our recent work has used molecular dynamics (MD) simulation methods to derive a general cohesive zone law for the fracture between two brittle materials under any mixed-mode loading conditions. Here we extend our method and use it to explore the effect of elastic constant mismatch between adjacent materials. In particular, we construct two bilayer structures where the cohesive energies and lattice constants of the constituent materials are kept the same, but the elastic constant mismatch of the two materials in one structure differs from that in the other. We then use MD simulations to study the fracture and to derive the cohesive zone laws for both structures. The effect of elastic constant mismatch on fracture will then be discussed.     

Fabrication of superhydrophobic 3-D braided carbon fiber fabric boat

A novel superhydrophobic carbon fiber fabric boat was prepared by combination of macro-scale rough surface and low surface energy material treatment. The loading capacities of the boats, fabricated from the resulting superhydrophobic fabrics, were also performed. The highest loading weight, 14.80 g, was obtained by a fabric boat treated with 12.0 wt.% HFTES. The striking loading capacity of the superhydrophobic boat is attributed to the air film trapped around the fabric surface.     

In-core fuel management strategy for the basket-fuel-assembly molten salt reactor

Molten salt reactor, with good economics and inherent reliability, is one of the six types of Generation IV candidate reactors. The Basket-Fuel-Assembly Molten Salt Reactor(BFAMSR) is a new concept design based on fuel assemblies composed of fuel pebbles made of TRISOcoated particles. Four refueling patterns, similar to the fuel management strategy for water reactors, are designed and analyzed for BFAMSR in terms of economy and security.The MCNPX is employed to calculate the parameters, such as the total duration time, cycle length, discharge burnup,total discharge quantity of ~(235)U, total discharge quantity of ~(239)Pu, neutron flux distribution and power distribution. The in–out loading pattern has the highest burnup and duration time, the worst neutron flux and power distribution and the lowest neutron leakage. The out–in pattern possesses the most uniform neutron flux distribution, the lowest burnup and total duration time, and the highest neutron leakage.The out–in partition alternate pattern has slightly higher burnup, longer total duration time and smaller neutron leakage than that of the out–in loading pattern at the cost of sacrificing some neutron flux distribution and power distribution. However, its alternative distribution of fuelelements cut down the refueling time. The low-leakage pattern is the second highest in burnup, and total duration time, and its neutron flux and power distributions are the second most uniform.     

螺栓加载拉伸技术的应用

主要介绍了直径较大的螺栓实现预紧的一种新方法－螺栓加载拉伸技术，讨论了螺栓加载拉伸技术原理，拉伸量计算方法，螺栓拉伸实现的步骤及校验的方法，这种技术对设备损伤小，密封组受力均匀，从而使容器密封的可靠性大大提高。     

Generating pallet loading patterns with considerations of item stacking on end and side surfaces

In late 1979 a two phase heuristic algorithm employing dynamic programming was presented by Steudel for solving the two-dimensional cutting stock problem where all the small rectangles were of the same dimensions, but withour any restrictions that the cutting be performed in a purely “guillotine” fashion. The algorithm was applied to solving the common problem of loading rectangular items of size l by w on a rectangular pallet of size L and W so as to maximize the number of items per layer on the pallet deckboard. In this paper, a new three-phase heuristic is presented which extends the 1979 recursive procedure and evaluates the option of stacking items on their end and/or side surface within the best loading pattern of bottom-stacked items. The resulting pattern is then projected into the third dimension to generate the total “cubic” pallet load. Computation results show that end and/or side stacking (when applicable) can yield average improvements in the range of 5% in items per pallet load.     

浅谈火工品药剂的粘合作用

本文探讨了火工品药剂的粘合作用，简要介绍了粘合剂的分类，对起爆药、烟火药粘合过程的理论进行了分析。对火工品药剂中粘合剂的用量提出了分析和建议。     

Using a CATS database for alternative machine loading

Industry is currently utilizing the computer to generate shop time standards. A logical extension of these systems is to include the ability to generate alternative standards, which then permits alternative machine routings. The purpose of this paper is to discuss the advantages of using alternative machine routings to improve the productivity of the machine shop. Through an example problem, it is shown that total production requirements are completed sooner by using alternative machines, and overall machine utilization is improved.     

可提高Buck型DC/DC转换器带载能力的斜坡补偿设计

提出了一种新颖的可提高Buck型DC/DC转换器带载能力的斜坡补偿设计。针对电流模DC/DC转换器在大占空比下的不稳定性,以及采用斜坡补偿后系统带载能力下降等问题,通过产生分段线性斜坡补偿信号并进行箝位,既保证了系统的稳定性,又提高了系统的带载能力。该电路基于0.5μm CMOS工艺设计,在不同的温度与电源电压下,经Hspice仿真验证,达到设计目标。     

The effect of loading time on flexible pavement dynamic response: a finite element analysis

Dynamic response of asphalt concrete (AC) pavements under moving load is a key component for accurate prediction of flexible pavement performance. The time and temperature dependency of AC materials calls for utilizing advanced material characterization and mechanistic theories, such as viscoelasticity and stress/strain analysis. In layered elastic analysis, as implemented in the new Mechanistic-Empirical Pavement Design Guide (MEPDG), the time dependency is accounted for by calculating the loading times at different AC layer depths. In this study, the time effect on pavement response was evaluated by means of the concept of “pseudo temperature.” With the pavement temperature measured from instrumented thermocouples, the time and temperature dependency of AC materials was integrated into one single factor, termed “effective temperature.” Via this effective temperature, pavement responses under a transient load were predicted through finite element analysis. In the finite element model, viscoelastic behavior of AC materials was characterized through relaxation moduli, while the layers with unbound granular material were assumed to be in an elastic mode. The analysis was conducted for two different AC mixtures in a simplified flexible pavement structure at two different seasons. Finite element analysis results reveal that the loading time has a more pronounced impact on pavement response in the summer for both asphalt types. The results indicate that for reasonable prediction of dynamic response in flexible pavements, the effect of the depth-dependent loading time on pavement temperature should be considered.