裂纹

Based on the alterative information of vibration mode and natural frequency in the presence of cracks, the thesis focus on the study of diagnosis index of cracks for plate and intelligent diagnosis of cracks using BP neural network.

本文主要依据板有无裂纹的振型和固有频率的变化信息，研究适于板的裂纹诊断指标，在此基础上，采用BP神经网络开展板的裂纹的智能诊断研究。

Three are three major actions that Mn effects fracture behavior in the alloy at room temperature, as follow: One is that Mn fines grains, antiphase domains and weakens dislocation clog, which retain formation of cleavage crackle. The second is that Mn decreases APB energy and promotes slop and cross slip, in particular, a large number of cross slip make deformed APBs transform from line type into zigzag type and the APBs interact and cross each other, resulting in propagation of cleavage cracks. The last is that Mn raises the relative proportion of cleavage strength to grain-boundary strength and then restrains formation and propagation of cleavage crack.

Mn对合金室温断裂行为的影响主要反映在三个方面，一是Mn的存在细化晶粒和反相畴，使得位错塞积程度减小，从而阻碍解理裂纹源的生成；二是Mn的存在提高解理强度与晶界强度的相对比值，从而抑制了解理裂纹的形成和扩展；三是Mn降低反相畴界能量、促进超位错的滑移、交滑移，特别是断裂前位错大量的交滑移使形变反相畴由直线型变为折线"Z"字型，反相畴界间的相互作用、相互交错阻碍了解理裂纹的扩展。

The germination, expansion and reciprocity of the crack inside the material embody on the crystal bound of the material. So, in this study we can change the bourgeon and extend condition of the tiny crack inside the material by design and control the crystal interface structure effectively and provide new research approach for the design and manufacture of the machinability ceramic.

由于材料的破坏和加工都决定于材料内部微裂纹生成的难易程度和扩展程度，而材料内部裂纹的萌发、扩展和相互作用集中表现在材料的晶界和相界面上；因此，本研究通过有效的设计和控制界面结构，改变材料内部微裂纹的萌生和扩展条件，为可加工陶瓷的设计和制备提供新的研究途径。

The problem of a curved rigid line or crack crossing the interface of the circular inclusion are studied by the principal part analysis method of Cauchy type integral equation. The singular stress index at the intersection and the singular stress at the angular regions near the intersection are obtained. The singular stress coefficients of rigid line at intersection and the stress intensity factors of crack at intersection are defined by using the singular stress.

利用Cauchy型奇异积分方程的主部分析方法对曲线型刚性线和曲线裂纹和圆夹杂界面的相交问题进行了研究，得出刚性线以及裂纹和界面交点处的奇性应力指数以及交点处角形域内的奇性应力，并利用奇性应力分别定义了刚性线在交点处的应力奇异因子和裂纹在交点处的应力强度因子。

The results showed that chemisorption of Hg atoms could facilitate dislocation emission and motion.

结果表明：加载裂纹吸附Hg原子后能促进位错的发射、增殖和运动；当吸附促进位错发射和运动达到临界状态时，脆性微裂纹就在原裂纹顶端或在无位错区中形核并解理扩展。

Self-fluxing Fe-Cr-Ni-B-Si alloy prowders are laser clad on medium carbon steel substrate of dimensions 80×35×10mm〓. The investigation results of this clad layer are: micro-defects, micro-cavity and occluded forin substance, are the micro-cracks and crack resourses in clad layer; crack of coating propagates along the boundary of two kinds of eutectic sutructure; The included angle θ between the cracking direction and laser scanning direction in multitrack overlapping clad is smaller than that in one-track clad because of crack propagating along crystalline growth direction and crystalline direction in overlapping zone being different from it in one-track clad.

在调质态的45〓钢表面，采用预置粉末法进行FeCrNiBSi合金的多道搭接激光熔覆，对其熔覆层进行分析表明：多道搭接激光熔覆层裂纹扩展方向与激光扫描方向间的夹角θ与单道熔覆时相比明显变小，前者θ0°，后者θ角基本都为90°，这主要是因为多道搭接时，搭接区结晶方向发生了变化以及裂纹沿结晶方向扩展所致；激光熔覆层裂纹大多是以覆层与基材交界面的孔洞、熔覆层内不同方向共晶团间的显微缩孔、夹杂物的边界等三种显微缺陷作为裂纹源，并沿低熔点物相形成元素偏析造成弱化膜的共晶团界面扩展延伸。

The rub-impact between rotor and stator often occurs because the rotor shaft stiffness decreases following the occurrence of the crack in the rotor shaft, and thus the coupling fault with rub-impact and crack is hackneyed fault type. Based on the nonlinear dynamical model of the cracked rotor-bearing system with rub-impact, the stability of the periodic motion and instability way were studied in unbalance-rotating speed plane and rotor/stator clearance- rotating speed plane and crack depth- rotating speed plane, and the main results were validated by the experiment.

转子轴承系统裂纹故障的出现会引起转子系统转静件之间碰摩故障的发生，因此裂纹碰摩耦合故障也是转子系统常见的故障类型，本文在裂纹碰摩耦合故障转子轴承系统的非线性动力学模型基础上，分析了系统在不平衡量-转速、碰摩间隙-转速、裂纹深度-转速等参数域内，周期运动的稳定性及其失稳规律，并用实验验证了主要理论结果。

Secondly, considering the complexity and heterogeneity of rock-like materials, two new models, namely the Inner Open Sliding Crack Model and the Single Wing Crack Model , are proposed. The two new models and the well-known Sliding Crack Model are consolidated as Zigzag Crack Model in this dissertation.

第二，针对岩石类材料的复杂性和非均质性提出两种新的模型：内张型滑动裂纹模型和单翼滑动裂纹模型，并将这两种模型和经典滑动裂纹统一为锯齿形裂纹模型。

The crack is modeled by distributed line spring ,the local compliance matrix of which is determined according to fracture mechanics.

管道的振动用Flügge方程来描述，通过将裂纹模拟为分布的线性弹簧，运用断裂力学理论，得到裂纹区域的局部柔度矩阵，从而建立外力作用处以及裂纹两侧区域的位移和内力的连续性条件对裂纹管道的功率流进行求解。

The experimental result shows that when the discharge time was more than 1.5μs, small crack emerged in the fuses due to mechanical force on the heated fuse, and the metallized layer would be evaporated as the crack became long enough to generate disruptive discharge. When the discharge time was less than 150ns, small crack emerged in the fuses due to the current heat, and the metallized layer would be evaporated as the crack became long enough to generate disruptive discharge.

实验结果表明：当熔丝的通流时间大于1.5 ms时，电流热效应产生的机械力使安全膜熔丝的金属层产生微小裂纹，当裂纹达到一定长度，两端发生击穿放电，金属层因蒸发而断开；当熔丝中通过较大的电流时，短时间内(50 ns)的电流热效应使熔丝金属层发生熔化产生裂纹，裂纹两端发生击穿放电，金属层因蒸发而断开。

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。