裂纹

And it can be turned into surface circumferential crack and surface axial crack .

套管裂纹缺陷中最危险的是表面裂纹，可分解成表面周向裂纹和表面轴向裂纹问题。

Firstly, achieving a new low and high cycle noninterfering loading, the high frequency induction local heating, the control of high cycle vibration frequency and amplitude, and the crack propagation real-time detection, an experimental system of L-HCCF at elevated temperature is established. Secondly, under two vibration frequency (50Hz and 100Hz), the contrast experiment of light and serious corrosion disc slots is done. It is found that the experimental L-HCCF life of serious corrosion disc is less than that of light's, but its dispersion is larger, and the experimental failure is identical with the service's.

首先，进行大量试验工作，提出了高低周疲劳载荷的新型加载方案，并解决了高频感应局部加温、振动调频及裂纹实时监测等多个技术难点，建立了涡轮盘全尺寸高温复合疲劳试验系统；验证试验做到了故障再现；接着进行了两种频比（振频50HZ与100HZ）的轻、重腐蚀盘的对比试验；由对榫槽第一齿进行裂纹实时跟踪，得出了枞树型榫槽的复合疲劳裂纹扩展特点规律；对榫齿断口进行的金相分析表明：裂纹首先由第一齿开始，断口系复合疲劳；试验结果显示：重腐蚀盘试验寿命较轻腐蚀盘有显著的下降，而且分散性较大。

Some typical torsion problems of a cylinder involving a straight,kinked or curvilinear crack were calculated.The obtained results for the case of straight crack...

对圆弧裂纹、曲折裂纹以及直线裂纹的典型问题进行了数值计算，并与用Gauss_Chebyshev求积法计算的直裂纹情形结果进行了比较，证明了方法的有效性和正确性。

In view of the concrete crack image characteristic, it emphatically discussed the recognition system three core issues. Firstly, it particularizes image preprocessing technology for reducing noise of concrete crack image. On the base of anglicizing the noise of specimen crack image and the characteristic of the noise , it propose the scheme that a hybrid filter will be used to reduce noise and introduce the principle of a hybrid filter.

随后，针对混凝土裂纹图像的特点，着重讨论了识别系统的三个核心问题：首先，详细讨论了对混凝土裂纹图像进行降噪的图像预处理技术，在分析了试件表明裂纹图像噪声的基础上，结合试件裂纹图像噪声的特点，提出组合滤波器的降噪方案，并介绍了组合滤波器的原理。

It follows that the microstructures of the cladding may not show a visible change after multi irradiation with the YAG pulsed laser beam, however, multi irradiation do promote the appearance of cracking on claddings.

试验结果表明：脉冲激光多次辐照，对熔敷层的组织及硬度影响不大；激光辐照次数的增多，促进了熔敷层裂纹萌生，其裂纹形态为沿晶高温液化裂纹；对基材热输入的增多，促进了基材再热裂纹的萌生

Under the ratios of various initial cracking relative length,height and volume of gas concrete beam,the whole curve of opening displacement s at several testing points about fracture toughness,fracture energy,and in the area of load,cracking-tip-opening-displacement,cracking tip opening displacement cracking-tip-area are researched systematically.

在本研究中对加气混凝土梁在不同初始裂纹相对长度、不同高度以及不同体积比例等情况下的断裂韧性、断裂能以及载荷—裂纹口张开位移—裂纹尖端张开位移—裂纹尖端前沿区若干测点张开位移全曲线进行了系统研究。

Crack sliding induced microcrack surface normal dilation and normal dilation induced microcrack further self-similar propagation are considered, the ineracting of sliding and propagation is clarified. The fourth-order tangent homogeneous stiffness tensor of shear microcrack is deduced, and at last the constitutive model of low porosity is expressed in increment formulation though unit sphere surface integral.

3在评述当前常用的微裂纹滑移准则的基础上，提出了本文的滑移准则，考虑了微裂纹滑移引起的裂纹面法向膨胀，以及由法向膨胀引起的微裂纹进一步扩展，阐明了滑移-扩展相互影响的细观力学机制。

The conclusions are: The sonic velocity determined by the material's properties is the upper limit of the crack velocity; Bridging fibers plays a key role in increasing the composite's toughness and stopping the crack's propagation; The semi-infinite crack propagating in infinite region with the fiber bridging traction action is equal to the semi-infinite crack propagating in strip.

结论有：(1)由材料性能决定的音速是裂纹传播速度的上限；(2)桥联纤维在增韧复合材料和组织裂纹扩展中起了关键作用；(3)受桥联纤维力作用的半无限长裂纹在无限域中扩展等效于半无限长裂纹在带域中扩展。

Through studying mechanism of drilling string failure in the action of interaction of cyclicstresses and corrosion, we find fracture source is accord with pitting corrosion inside surface ofdrilling string, crack from pitting corrosion lead to drilling string failure, the process of drillingstring failure is new drilling string → corrosion pit forming and crack initiation → corrosionfatigue crack propagation→piercement or fracture.

通过研究在钻柱交变应力和腐蚀的交互作用下的机理发现，腐蚀疲劳裂纹源与钻杆内壁蚀坑对应，蚀坑萌生裂纹造成钻柱失效，钻柱腐蚀疲劳破坏过程归结为：新钻杆—蚀坑形成及裂纹萌生—裂纹扩展—刺穿和断裂。

With analysing the the fatigue mechanism, the general mode of interply fatigue damage propagation is denoted by delamination length and crack density. Based on the power-law, the relationship between number of cycles and delamination length and crack density are established. The specimen is modeled as an equivalent six-ply material system. Starting with the analysis of interply stress, the interply shear stress under cyclic loading is calculated by using nonlinear three-demension FEA. According to the stage regularity of fatigue damage propagation, such models as average strain, effective modulus, ratio of delamination length and crack density, experimental relationship between crack density and effective modulus, are proposed by introducing subsection coefficient.

通过对疲劳机理的分析，确定了以脱层长度和裂纹密度表示的层间疲劳损伤演化的一般模式，利用指数法则建立了脱层长度和裂纹密度随疲劳循环周次变化的关系；从层间应力分析入手，以等效六层的材料模型对循环载荷下的层间剪切应力进行了三维非线性有限元分析；根据疲劳损伤扩展的阶段性，引入分段系数，分别建立了平均应变与载荷循环周次的分段线性模拟模型、有效刚度随载荷循环周次的变化关系模型、裂纹密度变化和脱层长度变化关系随载荷循环周次变化的分段线性模型以及疲劳裂纹密度和有效刚度关系的经验模型。

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。