岩石爆破损伤断裂的细观机理

基于现有岩石爆破机理和岩石细观损伤力学 ,认为岩石爆破损伤断裂过程包含有爆炸应力波的初期动态损伤演化阶段和后期爆生气体作用下的准静态损伤演化阶段 ,并分别建立了这两个阶段的损伤模型和断裂准则 ,阐述了岩石爆破损伤断裂的细观理论。     

Experimental study about nano-deformation field near quasi-cleavage crack tip

Using the nano-moiré method, we measure the near tip nanoscopic deformation on the [111] plane of single crystal silicon with a loaded quasi-cleavage crack running in the [110] direction. The measured strain distribution ahead of the crack tip agrees with the linear elastic fracture mechanics prediction up to 10 nm from the crack tip. Dislocations of Peierls type are detected and they extend from the crack tip over a length of hundreds of Burgers vectors.     

岩心孔隙介质中流体的核磁共振弛豫

弛豫时间是核磁共振研究中的一个重要参数,岩心孔隙介质流体的弛豫过程是自由流体弛豫机制、表面弛豫机制和流体的扩散弛豫机制共同作用的结果,它包含了丰富的孔隙和流体本身的信息. 弛豫时间和自扩散系数的测量及对弛豫时间的分析是核磁共振技术应用于岩心分析和石油勘测的重要内容.     

Method to calculate fatigue fracture life of control fissure in perilous rock

Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰand model-Ⅱstress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters (C and m) of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.     

Rock hyraces: a cause of San rock art deterioration?

San rock art sites are found throughout southern Africa, many showing signs of deterioration. In order to conserve this invaluable heritage, a long‐term multidisciplinary project has been launched to monitor the rate of their deterioration and determine the various chemical processes that are possibly contributing to the decay. This study was initiated to establish if Raman spectroscopy could contribute to this project and since rock hyrax colonies live in close proximity to many of these archaeological sites, the possible influence of their metabolic products on the deterioration process was investigated. The precipitates from the urine of rock hyraces were analysed with Raman and Fourier‐transform infrared (FTIR) spectroscopy. Where the urine was in contact with the faeces, the precipitates are a mixture of vaterite (a rare polymorph of CaCO₃) and the hydrated salt calcium monohydrocalcite (also rarely found in nature). On areas where this contact is at a minimum the common and stable polymorph of CaCO₃, calcite, is the main component. SEM micrographs and XRD analysis support the Raman and FTIR results. XRD, FTIR and preliminary GC‐MS analyses of hyraceum, the fossilised mixture of faeces and urine, identified an inorganic phase (potassium chloride, with small concentrations of other salts, e.g. vaterite and weddelite) and an organic phase, which is a cocktail of various aromatic compounds, mainly amides, alcohols and acids. These compounds could contribute to the crystallisation of these rare carbonates, as well as other uncommon salts detected on the cave walls, such as syngenite. The presence of phosphates in the urine may further act as a stabilizing agent. Copyright © 2007 John Wiley & Sons, Ltd.     

耦合时间精度对模拟飞行器自由运动特性的影响

将亚迭代技术引入流体动力学和刚体动力学方程的耦合求解,获得细长三角翼极限环运动的规律.探讨耦合时间精度对飞行器非定常运动特性的影响,细长三角冀的大迎角自由滚运动最终形成极限环振荡的周期性自维持运动,不同攻角自由滚振幅阶跃式的变化特点较好地吻合了自由滚试验的规律.对于多系统耦合问题,亚迭代耦合求解(耦合时间精度为二阶)对物理时间步长的依赖性不明显;而存在一阶时间滞后的解耦推进方法的数值结果强烈地依赖于物理时间步长选取,稍大的时间步长将导致非物理的数值结果.     

原子光谱和X射线衍射研究禄丰恐龙化石与围岩特征

迄今为止,禄丰老长箐是世界挖掘恐龙化石较多、涵盖时间最长(含有早、中两个侏罗纪的化石)的地区。老长箐恐龙化石的发掘,为古生物研究提供了得天独厚的实验基地。文章首次对该地区3个不同层位的恐龙化石及其围岩的成分和结构做了初步分析。首先采用原子发射光谱分析,发现化石及土样中的含钙量均较高(＞5%);但硅元素的含量则差别较大,在化石中的含硅量较低(3%～8%),围岩中的含硅量较高(＞10%);化石中的含磷量也较高。X射线能谱的进一步分析发现,化石中的主要化学成分是CaCO₃(66%), 其次是SiO₂(17%);围岩中的主要成分是SiO₂(＞80%),其次是CaCO₃(12%)。此外还发现,化石和围岩的最大区别是,化石中含有氟磷酸钙,而围岩中没有该成分。这一点可以作为鉴别伪化石的一个重要特征。文章为化石的鉴别、为人类研究禄丰老长箐恐龙的生态和演化提供了一定的实验依据。     

高压水射流作用下岩石破碎机理及过程的数值模拟研究

根据连续介质力学和有限元理论,给出了高压水射流破岩系统中流体和岩石的控制方程,并建立了相应的有限元列式．运用连续损伤力学和细观损伤力学理论,建立了适用于水射流破岩全过程分析的岩石损伤模型以及宏细观损伤的耦合模式．数值计算的结果较真实地反映了水射流破岩过程中,岩石的动态响应以及水射流动力学特性的演化过程,普通连续水射流破碎岩石主体所用的时间为毫秒量级,破岩的主要形式是卸载及射流冲击所产生的拉伸破坏,并呈“阶跃式”发展．数值计算与相关试验结果基本吻合,表明该分析方法是可行的,可用来指导高压水射流破岩理论的进一步研究及应用．     

单轴拉伸条件下细观非均匀性岩石损伤局部化和应力应变关系分析

岩石在拉应力状态下的力学特性不同于压应力状态下的力学特性．利用细观力学理论研究了细观非均匀性岩石拉伸应力应变关系包括:线弹性阶段、非线性强化阶段、应力降阶段、应变软化阶段.模型考虑了微裂纹方位角为Weibull分布和微裂纹长度的分布密度函数为Rayleigh函数时对损伤局部化和应力应变关系的影响,分析了产生应力降和应变软化的主要原因是损伤和变形局部化.通过和实验成果对比分析验证了模型的正确性和有效性．     

韧脆转变的一种细观随机模糊统计分析

对不同温度和应力状态下40Cr材料进行大子样宏观试验和细观观测,提出了一种新的材料断裂韧脆转变统计随机模糊模型。该模型认为,在统计意义上,材料的韧性断裂为空穴机制,临界空穴扩张比参数可以作为韧性断裂的判据;材料的脆性断裂可以用内嵌币状裂纹的脆性断裂模型来模拟,为此测量断裂特征长度,提出并具体计算了控制币状裂纹失稳扩张的细观临界应力强度因子;在韧脆转变区域内,这两种机理并存并相互竞争,为此提出了模糊准则。对模型参数进行了测量和统计分析,给出分布规律,给出了计算断裂特征的概率模型。计算了韧脆转变区域内的细观机制变化和宏观响应。结果表明,该模型及分析方法可以很好地模拟应力状态及温度对韧脆转变的影响。