隧道穿越高烈度地震区断层带围岩地震响应分析

考虑地震荷载特征及隧道特点,运用多点同时激振的动力时程分析方法,采用结构面单元与实体单元组合模拟断层带的方法,研究了某穿越断层破碎带铁路隧道在未支护条件下的动力响应特性。分析了沿隧道横向、纵向和竖向激振地震动工况下与断层破碎带接触部位所产生的位移差、加速度放大倍率和屈服单元等。结果表明：结构面单元与实体单元组合合理模拟了断层破碎带的地震响应特性;地震运动引起断层破碎带接触部位产生明显的位移差,横向输入地震动时位移差值最大,达到51.8 mm,而沿纵向和竖向输入时,位移差值仅为横向输入的44.3%和23.1%;同一高程处断裂带的加速度放大倍率明显大于混合花岗岩;断裂带与混合花岗岩过渡段出现明显的剪切屈服区域,且横向、竖向输入地震动时尤其突出;断层破碎带对隧道在地震动作用下的响应规律影响显著,穿越断裂带隧道的断裂带部位与过渡段为抗震设计控制性区域,应深入加强抗震措施研究。     

数据驱动的在线MW-MSPCA故障诊断

针对动态非平稳过程数据的时变性和多尺度性导致故障诊断准确率下降及故障准确定位难以实现的不足,引入滑动窗口多尺度主元分析(Moving window multi-scale principal component analysis ,MW-MSPCA)〖BP)〗,通过小波阈值消噪解决统计模型偏离与数据相关性降低之间的矛盾,并在各个尺度上利用滑动窗口主元分析实现模型更新,然后借助三维贡献图描述反映过程行为变化的各独立过程变量对统计过程的贡献程度,进而对故障准确定位,最后给出诊断准确性的定量评价机制。在对6135D型柴油机进行数值实验中,并通过与传统的多尺度主元分析及自适应多向主元分析比较,实验结果从故障的漏报率、误报率及诊断准确率三方面表明新方法能更好地实现传感器故障诊断。     

Compound machining of silicon carbide ceramics by high speed end electrical discharge milling and mechanical grinding

A compound process that integrates end electrical discharge (ED) milling and mechanical grinding to machine silicon carbide (SiC) ceramics is developed in this paper. The process employs a turntable with several uniformly-distributed cylindrical copper electrodes and abrasive sticks as the tool, and uses a water-based emulsion as the machining fluid. End electrical discharge milling and mechanical grinding happen alternately and are mutually beneficial, so the process is able to effectively machine a large surface area on SiC ceramic with a good surface quality. The machining principle and characteristics of the technique are introduced. The effects of polarity, pulse duration, pulse interval, open-circuit voltage, discharge current, diamond grit size, emulsion concentration, emulsion flux, milling depth and tool stick number on performance parameters such as the material removal rate, tool wear ratio, and surface roughness have been investigated. In addition, the microstructure of the machined surface under different machining conditions is examined with a scanning electron microscope and an energy dispersive spectrometer. The SiC ceramic was mainly removed by end ED milling during the initial rough machining mode, whereas it is mainly removed by mechanical grinding during the later finer machining mode; moreover, the tool material can transfer to the workpiece surface during the compound process.     

Formation and mechanical properties of Zr-based bulk metallic glass composites with high oxygen levels

Zr-based bulk metallic glass(BMG) composites with in situ formed Y 2 O 3 particle reinforcements were synthesized by proper additions of Y to ultrahigh-oxygen-containing glass-forming alloy precursors.Microstructures,thermal stabilities,and mechanical properties of the composites were investigated.Glass formation was greatly enhanced by Y additions in the alloys and the resultant particles were homogenously distributed in the glassy matrix,allowing for the fabrication of oxide dispersion strengthened BMG composites.The compressive strength and hardness increased by 10% and 20%,respectively,with the introduction of Y 2 O 3 particles.These results are significant for the design and production of Zr-based BMGs and BMG composites with improved properties using commercial high-oxygen content raw materials under industrial conditions.     

Electromagnetic modification of faceted-faceted Ni<Subscript>31</Subscript>Si<Subscript>12</Subscript>-Ni<Subscript>2</Subscript>Si eutectic alloy

In an electromagnetic field, the morphology of a binary faceted-faceted (FF) Ni31Si12-Ni2Si eutectic microstructure and the alloy’s mechanical properties were investigated. Hardness experiments demonstrated that the solidified ingots were significantly strengthened, and the hardness was improved to 63.1 and 786.6 on the Rockwell hardness C and Vickers hardness scales, respectively. Tests of friction and wear in stirred FF eutectic alloys showed excellent anti-fatigue and anti-adhesion wear performance. Alloy changed from an anomalous microstructure to a refined quasi-regular structure, and there was an increase in the lamellar microstructure fraction. The formation process of the refined quasi-regular microstructure and the resulting mechanical properties were investigated.     

模拟电路故障诊断的最小二乘支持向量机方法研究

介绍模拟电路故障诊断的现状及特点,提出一种基于最小二乘支持向量机的模拟电路故障诊断新方法.该方法可以对模拟电路有效地进行故障诊断,有较高的诊断效率.     

吹填淤泥自重沉积物理力学性质变化特征

吹填淤泥自重沉积阶段物理力学性质具有时空变异特征.通过对某围海造陆区吹填后淤泥自重沉积阶段物理力学性质的测试分析,对吹填淤泥的物理力学性质沿土层深度及自重沉积时间的变化特征进行了分析,结果表明:1)吹填淤泥的含水量(孔隙比)沿深度减小,变异性沿深度增加,强度沿深度明显增加,具有较大的变异性,应考虑变异性对选取土性指标的影响;2)吹填淤泥的含水量(孔隙比)在吹填施工完成前两个月减小速率很快,特别是表层1 m淤泥减小速率最显著,与相邻中间层淤泥层差距逐渐增大,两个月后整个吹填淤泥层进入缓慢失水状态.     

基于GA-BP算法的隧道围岩力学参数反分析

建立智能位移反分析系统,用其确定隧道围岩的力学参数.针对BP神经网络易陷入局部极小值和训练时间过长等缺点,利用遗传算法全局寻优能力优化BP神经网络的权值和阈值.结合均匀设计法在围岩力学参数初始域范围内设计实验方案,这样不仅减少了迭代时间和次数,还提高了预测精度.通过对绿春坝隧道围岩力学参数的反演,验证了该方法的可靠性及适用性.将反演得出的围岩力学参数代入到数值模型中进行计算,结果表明,数值计算值与现场实际监测值的误差分别为-8.9%和4.5%.     

铜铝冷轧复合薄带热处理工艺研究

利用金相显微镜和万能材料试验机,通过界面组织观察和力学性能测试,系统研究了铜/铝/铜冷轧复合薄带的热处理工艺,并讨论了热处理工艺参数对铜铝冷轧复合薄带界面组织和力学性能的影响规律.通过研究,得出如下结论:随退火温度升高或保温时间的延长,复合带强度降低,塑性增强;退火后复合带界面宽度为2～5μm,界面有脆性化合物CuAl2,CuAl和Cu9Al4生成;410℃退火,保温10 min时复合带综合性能最佳,为复合薄带的最佳热处理工艺.     

一种基于CSM模型的TBM刀盘比能预测方法

为了解决全断面掘进机在掘进时刀盘比能预测的难题,以岩石断裂力学为理论基础,深入分析了TBM滚刀的受力情况和破岩机理,基于CSM预测模型提出了一种新的TBM刀盘比能预测方法.通过建立滚刀与岩石相互作用的力学模型,推导出TBM刀盘的比能预测模型,并通过实例计算对刀盘的比能水平进行了量化研究,验证了模型的正确性.该预测模型基于滚刀破岩的机理,能够实时预测刀盘的比能,为TBM的刀盘优化设计以及性能预测提供了一定的理论依据.