基于关系模型的机载导航数据库快速解析生成方法

导航数据库可用于导航计算、导航台自动调谐管理等,是飞行管理系统所必须的数据源。为了能有效提高机载导航数据库的使用、更新及维护效率,大大减少相关工作人员的工作量,提出了一种基于关系模型的机载导航数据库快速解析生成方法,针对ARINC424协议中包含的大量数据对象进行建模,定义出协议中各个对象之间的逻辑关系和约束关系,并对数据结构进行优化,通过中间关系表确立各个数据之间的交叉引用关系,从而实现数据库的快速解析生成。测试结果表明,基于关系模型的机载导航数据库快速解析生成方法能有效提高数据查询效率,降低数据解析和生成的时间消耗,减少数据冗余,使数据库性能更优异。     

某大负荷涡轮过渡段设计探索

对某大负荷过渡段进行了探索设计和数值模拟。对比分析表明:在支板数很少的情况下，支板厚度分布对主流区的流动影响很小，主要通过叶型曲率分布来影响支板表面逆压梯度和分离。凹曲率和凸曲率搭配可以有效控制轮毂、机匣和支板叶尖的流动分离。可以通过支板周向倾斜改变支板叶型在S1流面的安装角，从而起到改变攻角效应和控制流动分离的作用。在条件允许的情况下应尽可能将支板部分或全部置于主流逆压梯度较小的区域以减小支板表面压力梯度和分离风险。      

A hybrid chemical modification strategy for monocrystalline silicon micro-grinding: Experimental investigation and synergistic mechanism

For high performance manufacturing of micro parts and features, a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition. The strategy, namely UV-light and IR-laser hybrid chemical modification (UVIR-CM) strategy, includes two steps, an ultraviolet light (UV-light) catalytic advanced oxidation and an infrared laser (IR-laser) assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon. The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation, cross-section transmission electron microscopy (TEM) observation, Raman spectroscopy analysis and nanoindentation test. Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’ IR-laser scanned area. And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium. But for the UVIR-CM strategy, a uniform and amorphous silicate layer is detected in a certain boundary. The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step. Attributing to synergism of photochemical, photothermal and kinetic effects induced by IR-laser, the modified layer displays layered structure with about 600 nm thickness, (2.7 ± 0.60) GPa nanohardness, and (93.7 ± 22.9) GPa indentation modulus. And the layered structure is amorphous layer, nanocrystal and micro-twins layer from the surface to the interior of sample. Consequently, it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area. Meanwhile, its original excellent mechanical properties also are maintained under a certain depth. The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.     

干式铣削Al-50wt%Si高硅铝合金刀具磨损与表面粗糙度评价

本文以Al-50wt%Si高硅铝合金为研究对象，采用单因素试验方法进行无涂层硬质合金刀具干式铣削试验，分析切削参数对刀具磨损和表面粗糙度的影响。结果表明：表面粗糙度受每齿进给量的影响最显著，随每齿进给量的增加而增加，当每齿进给量从0.07 mm/z增加到0.16 mm/z时，表面粗糙度增加2倍；刀具磨损受切削速度的影响最显著，随切削速度的增加而增加，当切削速度从140 m/min增加到260 m/min时，切削总长度降低3倍，而刀具后刀面磨损量仅是260 m/min速度下的0.8倍；表面粗糙度随刀具磨损的增加呈现先增加后降低的变化趋势，切削长度从350 mm增加到1 750 mm，刀具磨损量平均增加4.5倍，而表面粗糙度却下降2倍；硬质合金刀具主要的磨损形式为磨粒磨损、崩刃。