基于X-射线CT方法的岩石小裂纹扩展过程分析

岩石的小裂纹起裂及扩展过程是岩石力学研究的一个关键问题。对软硬两种砂岩进行单轴加载试验,同时用高分辨率的螺旋CT扫描机进行实时扫描。通过对获得的CT图像的分析处理发现,CT差值图像中的方差值与小裂纹的扩展速率有密切的关系,建立CT差值图像中的方差值与应力关系曲线,可以直观地看出:1)岩石样品中小裂纹起裂门槛值:软砂岩样品小裂纹扩展的门槛值为岩石强度的55%,小裂纹的扩展强度占整个强度的73%。硬砂岩小裂纹扩展的门槛值为岩石强度的64.5%,小裂纹的疲劳强度占整个强度的79%;2)小裂纹的扩展规律,即:在加载的初期岩石中小裂纹的扩展速率缓慢增大,在小裂纹扩展的门槛值出现之前快速下降,小裂纹扩展的门槛值出现之后又快速增加,最后当裂纹长度达到一定值时与长裂纹扩展速率基本一致。     

Re effects in model Ni-based superalloys investigated with first-principles calculations and atom probe tomography

The phase partition and site preference of Re atoms in a ternary Ni-Al-Re model alloy,including the electronic structure of different Re configurations,are investigated with first-principles calculations and atom probe tomography.The Re distribution of single,nearest neighbor(NN),next-nearest neighbor(NNN),and cluster configurations are respectively designed in the models withγandγphases.The results show that the Re atoms tend to enteringγphase and the Re atoms prefer to occupy the Al sites inγphase.The Re cluster with a combination of NN and NNN Re-Re pair configuration is not preferred than the isolated Re atom in the Ni-based superalloys,and the configuration with isolated Re atom is more preferred in the system.Especially,the electronic states are analyzed and the energetic parameters are calculated.The electronic structure analyses show there exists strong Ni-Re electronic interaction and it is mainly contributed by the d-d hybridization.The characteristic features of the electronic states of the Re doping effects are also given.It is also found that Re atoms prefer the Al sites inγside at the interface.The density of states at or near the Fermi level and the d-d hybridizations of NN Ni-Re are found to be important in the systems.     

土工织物防护工程反滤准则试验研究

土工合成材料的出现,为岩土工程施工技术带来了重要的影响。但将土工合成材料应用在堤岸防护工程中所出现的一些问题还有进行深入科学研究的必要。尤其是保土性准则一直是研究的热点问题。本文结合较大孔径织造布在堤岸防护工程中多年应用实践,通过室内反滤试验,野外淘刷试验及工程应用实例分析研究,提出了O90≤（2¹0）d90防护工程中织造布保土性设计新准则,突破了目前普遍采用的O90≤（1²）d90设计指标。