β单相区固溶温度对Ti-55531合金组织及性能的影响

研究了β单相区不同的固溶温度对Ti-55531合金片层组织参数及力学性能的影响规律。结果表明,经不同温度固溶处理,再经相同的时效处理后,合金的β晶粒尺寸随固溶温度的改变而改变,进而影响时效析出α片的含量及尺寸,最终导致合金力学性能的差异。当固溶温度在830～900℃之间时,随着固溶温度的升高,原始β晶粒尺寸增大,后续时效析出的α片长、宽及长宽比均先增大后减小,合金强度直线下降,塑性先降低后增加。固溶温度为860℃时,合金对应的强度塑性匹配最好。合金的断裂失效机制为以微孔聚集为主,沿晶开裂和穿晶断裂并存的混合断裂机制。     

服役工况下高速动车组齿轮箱箱体振动特性分析

为探究某高速动车组齿轮箱箱体在服役工况下的振动特性,对齿轮箱开展线路跟踪服役试验,通过分析测试系统在齿轮箱箱体多路线工况下采集的数据,研究其所真实反映的齿轮箱箱体及轴箱在实际运营线路中的振动特性.结果表明:齿轮箱箱体的振动比轴箱的振动更易受到列车速度变化的影响,且箱体的振动加速度与列车运行速度变化趋势基本一致;试验动车...     

中厚煤层切顶卸压无煤柱自成巷技术关键参数研究

现阶段切顶卸压无煤柱自成巷开采技术在薄煤层条件下应用较多,而对于中厚煤层的应用研究较少。为提高煤炭资源采出率,同时为避免以传统充填手段实现沿空留巷导致充填体位置产生应力集中,以切顶短壁梁为理论基础,以西山煤电集团公司杜儿坪煤矿62711工作面为工程背景,分析了切顶卸压无煤柱自成巷开采技术在中厚煤层的工艺流程及关键技术参数。通过理论分析和数值模拟的方法,分别对传统长壁式采煤法及切顶预裂爆破高度为4、6、8 m及切顶角度为5°、10°、15°、20°时巷道围岩应力分布及顶板位移情况进行了分析,结果表明：在合理的预裂爆破切顶高度和切顶角度条件下,不仅可以迫使顶板岩层在工作面回采后及时垮落并充满采空区,还可以有效切断巷道与采空区顶板岩层之间的应力传递路径,使得应力集中区域向实体煤深处转移,改善巷道围岩所处的应力环境,起到切顶卸压的作用。     

Influence of peak temperature during in-service welding of API X70 pipeline steels on microstructure and fracture energy of the reheated coarse grain heat-affected zones

In this investigation, thermal simulated specimens were used to investigate the effect of second peak temperature during in-service welding on characteristic fracture energy and microstructure feature of the subcritically (SC), intercritically (IC), supercritically (SCR), and unaltered (UA) reheated coarse grain heat-affected zones (CGHAZs). The API X70 high-strength pipeline micro-alloyed steel was subjected to processing during in-service welding by applying double thermal cycle shielded metal arc welding process with heat input of 9.3 kJ/cm and thermal cycles to simulate microstructure of reheated CGHAZs. This consisted of first thermal cycle with a peak temperature of 1350 °C, then reheating to different second peak temperatures of 600, 800, 1000, and 1200 °C with a constant cooling rate of 60 °C/s. Toughness of the simulated reheated CGHAZs were assessed using Charpy impact testing at −20 °C, and the corresponding fractographs, optical micrographs, and electron micrographs have been examined. It is found that accelerating cooling rate during in-service welding has an improving effect on the microstructure of CGHAZs. Owing to small heat-input and accelerating cooling, the grain size in reheated CGHAZs is relatively small and the brittle microphases are eliminated or minimized. The Charpy impact results show that the CGHAZ fracture energy is improved after the second thermal cycle. The SC CGHAZ showed higher absorbed impact energy and the IR CGHAZ had less absorbed energy, but the phenomenon of embrittlement in IR CGHAZ is not serious. Therefore, it can be concluded that the fracture energy of CGHAZ and IR CGHAZ can be improved by accelerating cooling with appropriate cooling rate.     

深切河谷区地应力场分布规律研究

 基于对南水北调西线工程7个坝址区水压致裂法地应力测试结果的统计分析,初步得出深切河谷区最大水平主应力量值随深度呈分段线性关系的结论。分析结果还表明在河谷埋深较浅部位(即应力释放区),最大水平主应力值随深度的增加幅度较小,而在较深部位(即应力集中区),最大水平主应力值随深度的增加幅度较大。此外,利用有限差分程序FLAC3D,对阿达坝址区的地应力场进行反演。研究结果表明：(1) 河谷卸荷作用对浅部谷坡的地应力场影响较大,在该区域采用水压致裂法确定地应力场误差可能会比较大;而对河床区域应力场方向的影响较小,采用水压致裂法来确定河床区域的应力场是可行、可靠的;(2) 不仅河谷区地应力场存在3个分区即应力释放区、应力集中区和应力平稳区,岸坡地应力场也存在上述3个分区;(3) 阿达坝址区河谷底应力集中范围在河床下60～140 m范围内;(4) 深切河谷区应力集中区的深度受岩体卸荷强弱程度和地形地貌的差异影响较大。     

飞秒激光行波泵浦BBO晶体光参量放大

采用飞秒钛宝石激光放大器二次谐波为泵浦源，行波泵浦ＢＢＯ晶体光参量放大器，获得了可调谐输出（０．４４～２．６μｍ），最大输出能量约４０μＪ／脉冲，测量了参量激光的调谐特性、能量分布和线宽，理论与实验符合较好。     

一种提升架的设计

介绍了带电超高压输电线路整体提升技术的设计思路,阐述了提升架的组成、工作原理和作用,并对提升架的稳定性进行了校核。     

细晶高强钢筋混凝土梁柱组合体非线性有限元分析

为了能对这种细晶钢筋增强混凝土结构的抗震性能有较为准确的定量分析,采用ANSYS有限元软件对十字形梁柱组合件进行了受力全过程的非线性有限元分析,并将分析结果与试验结果进行对比,从而进一步了解细晶高强钢筋混凝土梁柱组合件在反复荷载下的受力性能特点。有限元分析所得裂缝分布、钢筋应力分布以及梁端力-位移曲线反映出,高强钢筋混凝土框架梁柱组合件在低周反复荷载作用下梁端塑性铰区裂缝开展充分,钢筋应力最大,核芯区内钢筋未发生粘结破坏。有限元分析结果较好的描述了试件的受力特点和过程。     

Situation of China's Refractories Industry in Last Sixty Years

The annual output of China's refractories in 1949 was 74 thousand tons,and was 29.11 million tons in 2007,which was 65% of the world total refractories output.The export of China's refractory products and raw materials in 2008 was 6.18 million tons,which were exported to hundreds of countries and regions in the world.China is a big country in the field of refractories production and refractories export,which has devoted a lot to relative high temperature industry.     

一种基于数据平面可编程的软件定义网络报文转发验证机制

针对软件定义网络(SDN)中OpenFlow协议匹配字段固定且数量有限,数据流转发缺少有效的转发验证机制等问题,该文提出一种基于数据平面可编程的软件定义网络报文转发验证机制。通过为数据报文添加自定义密码标识,将P4转发设备加入基于OpenFlow的软件定义网络,在不影响数据流正常转发的基础上,对网络业务流精确控制和采样。控制器验证采样业务报文完整性,并针对异常报文下发流规则至OpenFlow转发设备,对恶意篡改、伪造等异常数据流进行转发控制。最后,构建基于开源BMv2的P4转发设备和基于OpenFlow的Open vSwitch转发设备的转发验证原型,并构建仿真网络进行实验。实验结果表明,该机制能够有效检测业务报文篡改、伪造等转发异常行为,与同类验证机制相比,在安全验证处理开销保持不变的情况下,能够实现更细粒度的业务流精确控制采样和更低的转发时延。