超声振动铣削加工Ti6Al4V的表面残余应力研究

建立了包含振动铣削、移除铣刀、载荷释放及降温等多个分析步的超声振动铣削三维有限元模型,对铣削表面的残余应力进行了仿真。通过有限元计算,得到了不同振动参数和铣削用量条件下加工表面的残余应力大小与分布情况,并根据振动切削表面残余应力的影响机制对仿真结果进行了分析。研究结果表明,对工件施加超声振动后,切削表面残余拉应力值明显减小;振动参数和铣削速度对残余应力的影响较大,而进给量对残余应力的影响较小,并通过相关实验验证了有限元仿真结果的正确性。     

热双金属片挠度值测量精度分析

热双金属片挠度值测量是检测其热弯曲一致性及稳定性的重要指标。介绍了热双金属片工作原理,分析悬臂梁法热双金属片热弯曲变形过程中产生的水平位移对各点挠度值测量精度的影响。利用CCD激光位移传感器非接触测量热双金属片被测面各点挠度值,通过补偿水平位移误差提高热双金属片各点挠度值测量精度,并实验验证各点挠度测量值的准确性。     

斜视航空相机的斜距离焦补偿

针对斜视航空相机成像时产生的离焦,设计了相应的调焦机构以补偿斜距离焦量。分析了斜距离焦原理,得出了斜距离焦补偿量的计算公式,并提出采用凸轮机构对斜距离焦量进行补偿。考虑传统的基于偏心凸轮的斜距调焦机构的理论模型具有数学近似的缺点,设计了理论模型没有进行数学近似的基于圆柱凸轮的斜距调焦机构。由于斜距调焦机构设计时是基于某一典型高度,当相机工作于其他高度时会产生剩余离焦量,文中分析了剩余离焦量产生的原因、处理方法和处理流程,从而使斜距离焦量在相机所有工作高度和扫描角范围内均得到补偿,为相机获得高质量图像提供了条件。最后,在实验室利用平行光管模拟了不同物距的成像,验证了提出的斜距调焦机构的有效性和准确性。     

标准养护室自动控制系统

本文针对当前标养室普遍存在的温湿度控制不准确 ,室内上下部温湿度不均匀等一系列问题 ,研制并建成一自动控制标养室。研究结果表明 :本自动控制系统能够将养护室内的温度控制在 (2 0± 2 )℃ ,相对湿度控制在 95 %以上 ,完全满足国家标准 (温度 2 0± 3℃ ,相对湿度≥ 90 % )的要求 ,且系统工作状况良好 ,能够较好的满足混凝土标准养护的要求     

土与结构物接触面物理力学特性试验研究

利用改进的直剪仪进行了砂土与结构物的接触面剪切试验 ,研究了不同接触面相对粗糙度对接触面物理力学性质的影响 ;并通过数字照相技术记录了接触面附近砂土颗粒的位移情况 ,分析了土与结构物接触面剪切破坏的变形机理。试验结果表明 ,存在接触面临界相对粗糙度Rcr,土与结构物接触面可依据Rcr 分为光滑接触面和粗糙接触面。光滑接触面剪切变形时沿土与结构物接触表面产生滑动破坏 ,接触面附近体积变化很小 ,剪切破坏时无明显的剪应力峰值 ,为理想弹塑性模式 ;粗糙接触面剪切破坏时在接触面附近产生应变局部化 ,形成剪切带 ,并伴有应变软化和剪胀现象。剪切带厚度约为 5D50 。     

Two types of a passive safety containment for a near future BWR with active and passive safety systems

The paper presents two types of a passive safety containment for a near future BWR. They are named Mark S and Mark X containment. One of their common merits is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. The PCV pressure can be moderated within the design pressure. Another merit is the capability to submerge the PCV and the RPV above the core level. The third merit is robustness against external events such as a large commercial airplane crash. Both the containments have a passive cooling core catcher that has radial cooling channels. The Mark S containment is made of reinforced concrete and applicable to a large power BWR up to 1830 MWe. The Mark X containment has the steel secondary containment and can be cooled by natural circulation of outside air. It can accommodate a medium power BWR up to 1380 MWe. In both cases the plants have active and passive safety systems constituting in-depth hybrid safety (IDHS). The IDHS provides not only hardware diversity between active and passive safety systems but also more importantly diversity of the ultimate heat sinks between the atmosphere and the sea water. Although the plant concept discussed in the paper uses well-established technology, plant performance including economy is innovatively and evolutionally improved. Nothing is new in the hardware but everything is new in the performance.     

Thermal hydraulic behaviors during loss of RHR system at mid-loop operation of Chinese 300 MWe PWR NPP

Thermal hydraulic behavior of nuclear power plant (NPP) is analyzed by using mechanistic computer code for loss of residual heat removal (RHR) system during mid-loop operation of Chinese 300 MWe two-loop pressurized water reactor is presented. In the absence of recovery of RHR or other accident management measures, the reactor core will be uncovered for a long term resulting in core heat-up, degradation and relocation to the lower plenum. The effectiveness of available mitigate measures, such as safety injection system, gravity feed from refueling water storage tank (RWST) and steam generator (SG) reflux-condensation, are investigated. Coolant injection is highly effective in halting the accident progression and make the core recovered. The cooling capability of SG reflux-condensation has a relationship with different availabilities of steam generators and decay heat power. 6 days after shutdown, 2SG operation can keep the water level at mid-line of hot leg. 12 days after shutdown, both 2SG operation and 1SG operation can keep the water level at mid-line of hot leg. The analyses also indicate that the cooling mechanism of safety injection system is more effective than gravity feed from RWST and SG reflux-condensation. Through confirming the success criteria of SG reflux-condensation, time windows can be devided. Then, event trees for loss of RHR system under mid-loop operation are built with considering the analysis results and abnormal procedure.     

脉冲堆余热导出安全性实验研究

实验研究了脉冲堆余热导出的安全性,给出了停堆后燃料芯体温度和堆水池散热能力随时间变化的实验数据及其分析方法和结果.实验及其分析结果表明,脉冲反应堆余热导出是安全的.     

反舰导弹目标分群的位置特征标准化方法研究

针对海上目标分群问题,介绍了反舰导弹对海上目标分群的两种常用的特征空间坐标及其特征标准化方法,提出了用相关系数、聚类树图和学生残差对海上目标分群进行聚类判定和综合检验的方法．以四种典型目标编队为例,运用Mablab7．0进行了层次化聚类编程计算和分析．结果表明,基于大地直角坐标的特征空间描述方式更有助于海上目标的数据聚类．     

地面水平度对武器系统射向的影响

由于地面不水平,武器在布设时,其射向基准发生了偏转．射向就会产生偏差,文中根据建立的数学模型。得到射向偏差的解析解,求解了水平度对射向的影响。结果表明水平度对射向的影响比较大,必须将其控制在一定的范围内,才能保证该武器系统的射击精度。