裂纹

New boundary integral equations for the torsion problem of an isotropic bar with curvilinear cracks are derived by using integration by parts and other techniques to the traditional boundary integral formulations. And the boundary integral equations for the torsion problem of an anisotropic bar with curvilinear cracks are also derived by using the isotropicalized boundary element method. Then the anisotropic problem can be solved on the base of the boundary element method of isotropic problem.

然后用各向同性化方法，将各向异性材料裂纹柱体的扭转问题转化为各向同性材料的问题，在各向同性材料裂纹柱体扭转问题的新的边界积分方程的基础上，推导出了适用于各向异性材料裂纹柱体扭转问题的边界积分方程，然后按已推导出的各向同性问题的边界元法求解。

On the research of the propagation of the fatigue crack in the past 10 years, Paris and Zheng-hart have developed good formulas of the propagation of the fatigue crack of metal , but of which only describe the process of the propagation of the fatigue crack.

在近几十年对疲劳裂纹的扩展的研究中，Paris和Zheng-hirt对金属材料疲劳裂纹扩展的研究给出了很好的扩展表达式，但都是对疲劳裂纹扩展部分过程的描述。

These T-stress effects depend on the sign and the magnitude of the T-stress as well as on the geometry of the microcrack arrangement.

当考虑T应力影响时，各向异性材料中的微裂纹对主裂纹的屏蔽效应比相同情况下各向同性材料中的微裂纹屏蔽效应更显著。

The mixed boundary problem was reduced to a system of singular integral equations by means of Fourier transform.

利用Fourier积分变换技术将混合边值问题转化为一对奇异积分方程，通过数值求解奇异积分方程获得含裂纹功能梯度板条分别在剪切和法向载荷作用下的I型和Ⅱ型应力强度因子，并讨论了材料的非均匀性和裂纹相对尺寸对裂纹尖端应力强度因子的影响。

First, FEM with nonhomogeneous elements is used to analyze the fracture problem of two dimensional FGM strips with inner cracks or edge cracks in the plane strain condition. The influences of geometric parameters, material graded modality and nonhomogeneity constant of the structure on the stress intensity factors at crack tips are investigated.

首先，本文采用该方法研究了平面应变状态下，含有内部裂纹和边裂纹的二维功能梯度条的断裂问题，分析了结构的几何参数、材料梯度形式和梯度参数对裂纹尖端应力强度因子的影响。

Therefore, on the foundation of abroad research, this text describes the first and second order of crack turning theory, the influence of plasticity zone of crack tip and fracture resistance orthotropy of material to crack propagating trajectory.

因此，本文在国外文献的基础上，对裂纹转折的一阶和二阶理论以及材料裂纹尖端塑性区和断裂韧性各向异性对裂纹扩展路径的影响进行了描述。

Based on the principle of PEC, surface cracks mainly affect the high frequency components and subsurface crack mainly affect the low frequency components, so the PEC signals can be analyzed in frequency domain, which can eliminate the influence of noises during measurement. A method of frequency spectrum separating point is proposed for flaw classification, which enhances the accuracy in classification of defects. The agreement between theory and experiment shows that the present method is valid and applicable.

通过对脉冲涡流的理论分析发现，表面裂纹主要影响脉冲频谱中的高频成分，而表面下裂纹主要影响脉冲频谱中的低频成分，因此可以将时域中易受噪声影响的脉冲涡流信号变换到频域分析，提出了"频谱分离点"的方法来对裂纹进行分类识别，提高了缺陷分类识别的正确率，理论分析和实验结果相一致，证明了该方法的正确性和有效性。

In the equation, the unknown parameters are determined by the crack initiation angle, the crack length and the angle between the direction of the maximum principal stress and the crack surface.

采用双曲线翼型裂纹路径和试验中所得翼型裂纹路径进行了对比分析，二者吻合得很好，验证了采用双曲线近似表示真实存在的翼型裂纹模型的正确性。

For both the collinear and wavy microcracks configurations, the critical linkage dominated fracture becomes less probable as the standard deviation of ligament size increases.

对于共线微裂纹和波折微裂纹构型，临界串接主导破坏概率均随着韧带尺寸标准方差的增加，即随着微裂纹随机分布不均匀性的增加而减小。

Usually, layer and vertical crack are caused by moulding,and horizontal and reticulate crack are caused by sintering .

通常层裂和竖向裂纹是机压所致，横向裂纹和网状裂纹是烧成造成的。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。