自密实混凝土叠合剪力墙屈服位移计算方法

在平截面假定的基础上,根据自密实混凝土(SCC)叠合剪力墙的受力特点,提出了其顶端屈服位移的计算方法,并用5个SCC叠合剪力墙试件的屈服位移试验值进行验证。通过计算分析,得到了轴压比、混凝土强度、分布钢筋的配筋率、锚固钢筋的配筋率与SCC叠合剪力墙屈服位移之间的关系。研究结果表明：在设计中选择经济合理的锚固钢筋配筋率、限制SCC叠合剪力墙的轴压比以及适当增加混凝土强度可以提高墙体在屈服状态的变形能力;提出的计算方法合理可靠,求得的计算值与试验值吻合较好。     

强度折减法在边坡稳定性分析中的应用

以一均质土坡为例,首先采用有限元整体强度折减法计算,在此基础上分别选取塑性剪切应变率大于2.0e-5和塑性区为局部强度折减法的折减范围,通过局部强度折减得到边坡滑裂带分布和稳定安全系数,分析不同折减范围下边坡稳定安全系数、特征点位移以及滑裂带的变化规律。比较天然状况和稳定渗流状态下局部强度折减和整体强度折减的计算结果。结果显示:两种方法得到的稳定安全系数基本一致,但折减范围的选择对计算结果影响很大,折减塑性剪切应变率大于2.0e-5的范围得到的稳定安全系数较小。     

惯性矩二次变化变截面梁柱几何非线性分析

为研究考虑剪切变形的变截面梁杆结构几何非线性问题,应用Timoshenko梁理论,采用位移、转角独立插值的方法,获取考虑剪切影响的惯性矩二次变化变截面梁单元的形函数;从严格的虚功增量方程出发,建立同时考虑轴力、剪切、弯曲效应及其耦合项的平面变截面梁柱单元几何非线性增量平衡方程,得到惯性矩二次变化变截面梁单元大位移切线刚度阵;与经典算例进行对比,验证了本文方法的精确性与有效性．     

复杂情况下蒸汽管路的设计与施工

根据蒸汽管路的设计与施工及实际运行情况,介绍了在复杂环境下蒸汽管路的设计与施工应该注意的事项,为同行类似的蒸汽管路设计与施工提供参考.     

两相驱动型时栅位移传感器测角系统误差建模与分析

为了进一步拓展时栅位移传感器的应用范围,在传统场式时栅位移传感器测角系统的基础上,提出了一种两相驱动型时栅位移传感器测角系统,该系统以低分辨率、低成本的圆光栅和直接数字频率合成器构成了一种新的“时间行波”,结合传统时栅位移传感器的处理技术,构成一个新的测角系统。对该测角系统的误差模型进行研究,实验结果表明：该测角系统的主要误差成分为光栅信号的不正交、不等幅与残余直流电平三项误差源,通过该误差模型可以有效地减小时栅位移传感器的原始误差、提高了测角系统的测量精度,精度达到±3.2″。     

On the calibration of cohesive parameters for refractories from notch opening displacements in wedge splitting tests

Cohesive elements are commonly used to describe crack propagation in heterogeneous materials with toughening mechanisms. This work aims to provide a guideline on how these fracture parameters can be calibrated using notch opening displacements (NODs) measured via digital image correlation and force data from wedge splitting tests (WSTs). Weighted finite element model updating was applied to calibrate material and boundary condition parameters in the same framework. The influence of each parameter on force and NOD data are given together with uncertainties for the calibrated parameters. Numerical results were in very good agreement in terms of splitting force, NOD, displacement and gray level residual fields. It is shown that images obtained during WSTs focusing on the crack path (i.e., hiding the loading region) can be used to drive numerical simulations and obtain cohesive parameters.     

聚合物微球在油田深部调驱技术中的研究进展

深部调驱技术作为目前提高低渗非均质油藏采收率的有效办法之一,聚合物微球因具有良好的封堵性能和深入性能得到了广泛研究。本文详细介绍了聚合物微球在地层中的深部调驱机理,介绍了聚合物微球的制备方法,综述了聚合物微球的研究内容和研究现状,并指出引入纳米材料合成功能性聚合物微球能有效解决聚合物微球的稳定性,对低渗油藏后期开发具有重要意义。     

Morphological and microchemical phenomena in the high-temperature oxidation of binary Al-Li alloys

The high-temperature oxidation behavior of binary Al-Li alloys has been characterized by scanning electron microscopy and secondary ion mass spectrometry in order to understand the mechanism of rapid oxidation in these alloys and to correlate the oxide morphology to its microchemistry. The oxide scale developed on polished specimens during short exposures in air at 530°C shows characteristic nodules that usually nucleate at grain boundaries. Examination of the alloy surface after removal of the oxide layer shows that the initial growth of the oxide nodules occurs laterally in addition to thickening normal to the oxide/alloy interface. Microchemical analysis of the oxide film with a scanning ion microprobe reveals a thick Li-oxide layer at the oxide/gas interface indicating preferential oxidation of Li at the free surface; the rest of the oxide film is composed of both Al- and Li-rich oxides, probably Li₂O and LiAlO₂ The presence of trace impurities (K, Na, F, and Cl) in the oxide scale was also detected. A microstructural model for the development of the oxide film in the Al-Li system is presented on the basis of both morphological and microanalytical data obtained in this study; this new model is compared with existing models.     

三自由度平面全柔顺并联机构运动学分析

针对传统方法求解全柔顺并联机构Jacobian矩阵存在奇异性的缺陷,基于三自由度平面全柔顺并联机构的伪刚体模型,提出一种微位移法来求解机构的Jacobian矩阵。先建立机构的伪刚体模型,并采用传统方法和微位移法得到机构的输入输出Jacobian矩阵;通过HyperMesh软件仿真和实验测试分别得到机构动平台中心点位移的仿真值和实验值。最后,将两种方法得到的理论值分别与仿真值、实验值进行对比。对比结果表明:与传统法相比,微位移法的计算精度较高,误差较小,且验证了Jacobian矩阵的有效性,为全柔顺并联机构的运动特性分析提供了参考。     

SLOW PROPAGATION OF FATIGUE CRACK NEAR THRESHOLD

The effect of pearlite interlamellar spacing(d)from 0.31 to 0.77 μm of T8 steel on fatiguecrack propagation near threshold has been investigated at different stress ratios(R).Theclosure stress intensity factor(K_(cl)),the threshold value(ΔK_(th))and crack tip opening dis-placement range(ΔCOD)were measured.The results show that pearlite interlamellar spac-ing in this range has no effect on K_(cl),but has effect on the threshold value in low stress ratio.The threshold value is higher for materials with larger interlamellar spacing.No matter whatthe stress ratio is,during the propagation near threshold,the propagation rate will be thesame,provieded the crack tip opening displacement range is the same.Metallurgical examinations were also carried out to show that the crack propagationpath is sensitive to mierostructure.The crack always propagates along either boundary ofpearlite colony or ferrite lamellar in pearlite.