ITER校正场线圈剪切销氧化铝涂层低温绝缘性能研究

采用大气等离子喷涂方法在316LN不锈钢剪切销表面喷涂了Al₂O₃+3%TiO₂绝缘涂层,采用NiAl作为粘结层,得到了性能优良的绝缘保护涂层。按照ITER实际运行环境,采用ANSYS分析方法对剪切销进行应力分析,并在低温(液氮,77K)环境下对剪切销加载后进行循环往复摩擦磨损试验。循环5000、10000以及30000周后采用2点和3点法分别测定了涂层的表面电阻和体积电阻,剪切销表面电阻率均大于10⁹Ω•m^-2,体积电阻率均大于10¹⁰Ω•m,表明涂层具有较高的绝缘电阻,满足ITER所需工程条件。     

Numerical study on the shear-flow behavior and transport process in rough rock fractures

This paper presents a systematic research for understanding mechanical shearing effects on the fluid flow and the solute transport behavior of rough fractures through a numerical simulation approach. The aperture fields were modeled based on a real rock fracture geometry and the normal displacement obtained from the shear-flow test. The fluid flow through the rough fracture under shear was simulated using a finite element code that solves the Reynolds equation, and the transport behavior through the rough fracture under shear was simulated calculating the advection–dispersion equation. The results show that the fracture apertures increase as the shear displacement increases, with a few major flow channels detected through the fracture. The shear-induced flow channels increase both flow connectivity and transport connectivity, which accelerate the movement of solutes in a particular direction and lead to early breakthrough of the contaminants. Adsorption, acting as a retardation term, has a decisive influence on the transport process. These results can give a basic knowledge of the hydromechanical and solute transport progress through fracture, and will be helpful to safety assessment for high-level radioactive waste disposal facilities.     

弯折波导杆的超声斜入射方法*

波导杆技术是一种有效的超声辅助检测方法,在提升高温关键承压设备安全运行方面具有重要作用。现有的波导换能器因直入式发射声波,常被用来在线监测壁厚的腐蚀进程,难以对指定方向的缺陷进行有效检测。为了解决这个难题,基于斯涅耳定理以及导波的频散特性提出了一种弯折结构的波导杆来实现超声斜入射。首先分析了弯折波导杆中水平剪切波的传播特性,探究了波导杆的厚度、弯折角度对杆中声波传播的影响规律;然后,进一步研究了弯折波导杆在半无限空间内的声束指向性;最后通过一对弯折波导杆在线检测结构内部缺陷的试验证明了波导超声斜入射的应用价值。研究结果为基于斜入射技术的波导超声在线监测提供了坚实的理论基础。     

银铜钛膏状钎料钎焊石墨和铜合金接头的微观组织及性能

利用银铜钛(Ag-Cu-Ti)膏状钎料采用真空钎焊的方法对两种不同石墨和铜合金进行钎焊连接实验,研究了钎焊温度、中间缓冲层、母材尺寸等工艺参数对接头性能的影响。采用自行设计模具对接头的剪切强度进行了测试,利用扫描电镜和配带的X射线能谱分析仪分析了接头界面组织形貌及元素物相成分。研究结果表明:当钎焊温度为910℃,保温时间10min时,Ag-Cu-Ti膏状钎料能够与石墨和无氧铜两侧母材形成良好的结合界面;与GA石墨相比,阿泰克石墨与无氧铜接头强度更高;采用1mm无氧铜做中间缓冲层钎焊石墨和铬锆铜时,能有效缓解钎焊热应力,接头强度有明显提高。     

残余应力的超声横纵波检测方法

基于声弹性原理,研究板材厚度方向、螺栓轴向方向(以下简称z轴方向)宏观残余应力分布的超声无损检测方法。针对被测构件厚度不均匀对应力检测精度的影响非常大、检测原理繁杂不适合工程应用、拉伸实验中拉伸形变对应力系数测量精度的影响很大等问题,采取超声横波、纵波相结合的方法重新推导检测公式,并提出采用一发一收模式进行拉伸实验,通过对实验数据进行拟合,由公式计算出声弹性系数代替应力系数。然后结合插值、互相关等算法,采用VC++编制z轴方向残余应力超声检测软件并搭建检测系统。分别对性能为A2-70,4.8,8.8,长度依次为135 mm,100 mm,100mm的M20的螺栓进行拉伸实验,比对计算拉伸应力与检测拉伸应力,结果表明,该测量系统的绝对误差限为20 MPa,相对误差小于25%,且应力值较大时,相对误差有所减小,当应力值大于100 MPa时,相对误差小于5%,非常实用。     

微小型矩形槽道平板热管传热性能的数值模拟

在充分考虑槽道内汽-液界面剪切摩擦力下,建立了微小型矩形槽道平板热管的数学模型,通过迭代计算得出工质质量流量、流体和蒸汽平均流速、汽一液界面弯月面半径及蒸汽和液体压力沿轴向分布规律,最后对热管外壁面温度值的计算结果和实验结果进行了比较,两者数值基本一致,证明了所建数学模型与实际相符,对热管的理论分析具有指导意义。     

The propagation of Quasi-static region during granular impact

In this paper, through experiments and DEM simulations, it is found that there is a ring-shaped region named Quasi-static Region between the particles expanding outward and the particles collapsing inward during the impact process. Quasi-static Region is always generated from the impact point at the same time, and then spreads out at a uniform speed. During the propagation of Quasi-static Region, the velocity of the particles in the particle extend region varies linearly in space and time. And the change rate is only related to the properties of the particle system. The simulation results show that the particle flow in Quasi-static Region is elastic-inertial flow, while the particle flow expanding outward and collapsing inward is inertial flow.     

Structural design and impact resistance of three-dimensional structure-reinforced flexible polymer composites

Three-dimensional (3D) structure-reinforced flexible polymer composites have great potential as personal protective materials. These composites exhibit excellent mechanical properties and failure mechanisms than typical rigid composites because of the complex dynamic reaction processes caused by the 3D structure in response to impact. This paper comprehensively reviews the impact resistance mechanism of 3D structure-reinforced flexible polymer composites by combining current results with relevant investigations. 3D woven fabric reinforcements and flexible matrix materials of flexible polymer composites systems are presented in this paper. The classification for 3D woven fabric reinforcements is reviewed, as well as the effect of reinforcement structures on the impact resistance of the flexible composites. Furthermore, several flexible matrix are introduced. Several external factors affecting the impact resistance of composites are then discussed. Finally, the impact damage mechanism of 3D structure-reinforced flexible polymer composites is summarized and analyzed.