化学灌浆在新疆达坂隧洞管片裂缝处理中的应用

本文介绍了新疆达坂隧洞管片裂缝的化学灌浆修补工艺,通过有效的检测手段对裂缝的成因、性质作出精准的判断,实施了有针对性的修补方案,验证了钻孔灌浆与表面涂刷在裂缝修补中的适宜性,成功解决了裂缝修补施工难题,选用的化学灌浆材料经济适用,为类似工程提供了借鉴。     

氢蚀对15CrMo钢疲劳裂纹扩展寿命的影响

对15CrMo钢在氢蚀环境下和疲劳裂纹行为作了研究，重点考察了不同温度、压力和时间等情况下的扩展特性，并找出了对Paris公式中系数的影响趋势。     

控制板坯三角区裂纹的措施

从转炉钢水、工艺参数、工艺操作和连铸设备等方面，分析了影响板坯三角区裂纹的原因并提出控制措施。     

双栅极空气计数器猝熄脉宽算法

针对双栅极空气计数器放电猝熄的物理过程，提出了计数器猝熄脉宽的一种新算法。该算法理论简便实用，能够较好地用于计数器的优化设计，算例结果验证了这种算法的有效性。     

磁光盘径向偏摆测试的新方法

简述研制磁光盘机械特性测试仪的必要性，介绍径向测试可供选择的几种方案，并进一步提出光栅定标过道信号的测试方法。     

现浇楼板裂缝产生原因及处理措施

介绍了某学生公寓工程质量事故的鉴定过程。依据相关标准对该学生公寓进行了倾斜观测、沉降观测、钢筋检测、楼板厚度检测、混凝土强度检测等现场检测工作，并观测了现浇板开裂情况，分析了其形成原因，提出了相应的处理措施。     

Numerical investigation on stress concentration of corrosion pit

Localized (pitting) corrosion has been observed in steel and high-strength aluminium alloys in aqueous environments and has been identified as a potential origin for fatigue crack nucleation. In the present study, under uniaxial tension loading, stress distribution at the semi-elliptical corrosion pits has been investigated by conducting a series of three-dimensional semi-elliptical pitted models, systematically. Based on the finite element analyses, it is concluded that pit aspect ratio (a/2c) is a main parameter affecting stress concentration factor (SCF). An attempt has been made to construct simple equations to SCF depending on characteristic of pit parameters. At the bottom of hemispherical pit, contribution of secondary (premature) pit formation to SCF is very pronounced.     

Failure analysis of a boiler tube in USC coal power plant

This paper presents failure analysis of final superheater tube in ultra-supercritical (USC) coal power plant. Visual inspection was performed to find out the characteristics of fracture of the as-received material. And the micro-structural changes such as grain growth and carbide coarsening was examined by scanning electron microscope. Detailed microscopic studies were made to find out the behavior of the scale exfoliation on the waterside of tubes. From those investigations, the creep rupture may be caused by the softened structure induced by carbide coarsening and accelerated by the metal temperature increase by the impediment of heat transfer due to voids.     

Damage tolerance investigations on rails

The paper summarises damage tolerance investigations on railway rails which the authors have carried out in the context of the German-French joint project NOVUM (novel methods for quantitative prediction of rail performance at increased service loads) [Girardi L, Heyder R, Dider L, Boulanger D. IDR2-NOVUM promises lower rail maintenance costs. Railway Gazette Int 2005;(July):439-41[1]]. The investigations include the determination of the crack driving force as a function of the various loading components a rail is subjected to and the simulation of residual lifetime. Features such as the local load input at the rail-wheel interface, dynamic effects and statistical aspects of crack resistance are explicitly taken into account.     

A fast dual boundary element method for 3D anisotropic crack problems

In the present paper a fast solver for dual boundary element analysis of 3D anisotropic crack problems is formulated, implemented and tested. The fast solver is based on the use of hierarchical matrices for the representation of the collocation matrix. The admissible low rank blocks are computed by adaptive cross approximation (ACA). The performance of ACA against the accuracy of the adopted computational scheme for the evaluation of the anisotropic kernels is investigated, focusing on the balance between the kernel representation accuracy and the accuracy required for ACA. The system solution is computed by a preconditioned GMRES and the preconditioner is built exploiting the hierarchical arithmetic and taking full advantage of the hierarchical format. The effectiveness of the proposed technique for anisotropic crack problems has been numerically demonstrated, highlighting the accuracy as well as the significant reduction in memory storage and analysis time. In particular, it has been numerically shown that the computational cost grows almost linearly with the number of degrees of freedom, obtaining up to solution speedups of order 10 for systems of order 10⁴. Moreover, the sensitivity of the performance of the numerical scheme to materials with different degrees of anisotropy has been assessed. Copyright © 2009 John Wiley & Sons, Ltd.