漕河渡槽深厚卵石层钻探取芯样技术探讨

对深厚卵石层钻探完整取芯样问题一直是水电勘探中的一大难题,近十年来由于采取了SM植物胶金刚石钻进工艺,岩芯采取率和钻进效率都有一定的提高;随着实践经验的积累和技术参数、配制方法的不断调整,此钻进工艺得到了不断完善.槽河渡槽是南水北调中线工程河北省段最大的建筑物,河床段卵石层深厚且含砂量小,钻探取样难度极大;就漕河渡槽深厚卵石层勘探中钻具的选用、技术参数的选择及植物胶配制方法、注意事项、取芯样技术进行了较详细的叙述并进行了总结,可供以后类似地层勘探时参考.     

航空发动机燃烧室机匣破裂安全性预测方法

针对航空发动机燃烧室机匣安装座环焊缝疲劳寿命的研究,提出了一种安装座焊接结构双轴拉伸模拟件的设计方法。首先,通过分析机匣安装座的载荷工况及几何特征,给出了相应的设计准则和几何等效分析,同时设计出模拟件的雏形。然后,根据优化目标提出了一种优化数学模型,以有限元计算的方式讨论了模拟件在中心试验区直径D₁,夹持臂楔形角度ω,安装座通孔直径D₂的3种尺寸变量下的应力变化规律,进而确定了模拟件的最终尺寸。最后,采用该模拟件进行双轴拉伸疲劳试验。试验结果表明,裂纹源出现在模拟件试验区的焊缝处,并且沿着焊缝向两侧进行扩展,证明了该设计的合理性。

     

不锈钢Ⅲ型试样的氢致开裂和应力腐蚀

研究了奥氏体不锈钢Ⅲ型试样的氢致开裂和应力腐蚀。结果表明,动态充氢时Ⅲ型试样也能发生氢致滞后断裂,且裂纹沿原缺口平面形核和扩展。从而可获得宏观平滑的扭转断口,但断口上存在少量沿45°面的二次裂纹,一系列实验表明动态充氢能促进奥氏体不锈钢室温蠕变,故在恒扭矩下充氢能使扭转角不断增大,直至试样被扭断。奥氏体不锈钢Ⅲ型试样在42%沸腾MgCl₂溶液中也能发生应力腐蚀开裂,且裂纹在与缺口平面成45°的平面上形核和扩展。实验表明,无论是Ⅰ型还是Ⅲ型,应力腐蚀的门槛值均比氢致滞后断裂门槛值要低,例如K_ⅠSCC/K_ⅠX=0.18,K₍ⅠH/K_ⅠX=0.58,K_ⅢSCC/K_ⅢX=0.13 K_ⅢH/K_ⅢX=0.62。     

Numerical study of compact shear (Mode II) type test specimen geometry

The Iosipescu shear test specimen geometry has been investigated by a number of research workers in recent years with conflicting results. The paper describes a numerical study of a compact shear test specimen, based on the Iosipescu geometry, which is proposed to investigate size effects in shear failure. A range of geometries has been studied and the extreme cases are reported. Results are presented for the largest absolute principal stresses together with a detailed study of the stresses between and around the roots of the two notches introduced in the test specimens. The results for the largest absolute principal stresses show that tensile stresses are created at the roots of the two notches. These tensile stresses may result in Mode I failure and probably account for the Mode I or mixed mode fracture observed in tests using the Iosipescu geometry. The results for the distribution of stresses between the roots of the two notches show that deep notches increase the likelihood of shear fracture prior to tensile failure. Shallow notches give a stress distribution similar to that developed in the indirect tensile test and hence tensile failure is likely to precede shear failure in such cases. Further numerical and experimental work is proposed.      

用Charpy试样研究核压力容器钢的韧性转变温度曲线

用一个标准Ｃｈａｒｐｙ试样及试验过的该试样的两个半截试样所获得的８个“再造Ｃｈａｒｐｙ复合试样”评定核压力容器用Ａ５０８ＣＬ３钢冲击韧性或断裂韧性的温度转变曲线。研究结果表明，用这种方法可得到一条较为可靠而完整的核压力容器钢的冲击韧性或断裂韧性随温度的转变曲线。这相当于在核监测计划中，只需取出一个Ｃｈａｒｐｙ试样即可得到完整的材料性能曲线，这对于提高核压力容器中子辐照脆化监测的可靠性很有价值，特别是对于运行时间较长（堆芯内监测试样数量已经不多）的核容器寿命预测和安全监视尤为重要。     

不同方法评定核压力容器用A508CL3钢动态断裂韧性的比较

采用示被冲击试验及预制疲劳裂纹Ｃｈａｒｐｙ试样，通过几种不同的单试样试验方法对核压力容器用Ａ５０８ＣＬ３钢的动态断裂韧性进行了评定，比较了各种方法的优缺点。研究载荷能量法过高地评定了材料的动态裂韧性值；而柔度变化度法的评定值则过低，断口延伸带宽度测试法的评定结果具有较大误差，且试验过程复杂，成本较高；能量修正法是一种方便而精确的评定核压力容器钢动态断韧性的单试样方法。     

45号钢带孔板件磁记忆检测试验研究

研究了带单个圆孔的45号钢板状试件在拉伸载荷作用下的磁记忆信号变化规律,并使用TSC-1M-4应力集中磁检测仪,对试件在不同应力阶段进行了检测和数据分析。结果表明:磁记忆检测信号特征参量的变化规律能准确地表征试件应力集中区域位置,是检测板状材料应力集中程度的有效方法。     

FRP筋应力松弛试样端部锚夹方法研究

将FRP筋作为预应力筋使用,必须了解其应力松弛特性.要测定FRP筋的应力松弛特性,关键是要找到一种有效的试样端部锚固方法.FRP筋一般的锚具系统应用于松弛特性测试时存在这样或那样的缺陷,为此本文提出了一种创新的测试FRP筋应力松弛特性的试样端部加强锚固的方法,实现了松弛试验时端部近似为零的滑移,保证了试验段应变的恒定,从而可准确测定FRP筋的应力松弛性能.     

X80级管线钢管屈服强度测量影响因素的分析

针对西气东输二线管道用X80级螺旋埋弧焊管生产中,在不同位置、采用不同形式试样所测得的屈服强度结果存在的差异,通过分析指出产生这种差异的主要原因在于：材料的各向异性,试验设备的精度及试样装卡,试样形式,试验方法的选择,时效现象,包辛格效应的影响。     

Generating Cloned Goats by Somatic Cell Nuclear Transfer—Molecular Determinants and Application to Transgenics and Biomedicine

The domestic goat (Capra aegagrus hircus), a mammalian species with high genetic merit for production of milk and meat, can be a tremendously valuable tool for transgenic research. This research is focused on the production and multiplication of genetically engineered or genome-edited cloned specimens by applying somatic cell nuclear transfer (SCNT), which is a dynamically developing assisted reproductive technology (ART). The efficiency of generating the SCNT-derived embryos, conceptuses, and progeny in goats was found to be determined by a variety of factors controlling the biological, molecular, and epigenetic events. On the one hand, the pivotal objective of our paper was to demonstrate the progress and the state-of-the-art achievements related to the innovative and highly efficient solutions used for the creation of transgenic cloned does and bucks. On the other hand, this review seeks to highlight not only current goals and obstacles but also future challenges to be faced by the approaches applied to propagate genetically modified SCNT-derived goats for the purposes of pharmacology, biomedicine, nutritional biotechnology, the agri-food industry, and modern livestock breeding.