裂纹

Firstly, the equation for stress intensity factors under static uniform pressure is used as the reference case, and then the weight function for a thick-walled cylinder containing a radial edge crack can be worked out. Secondly, the dynamic stresses in uncracked thick-walled cylinders are solved under internal impulsive pressure by using mode shape function method. The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary conditions, and the history and distribution of dynamic stresses in thick-walled cylinders are derived in terms of Fourier–Bessel series. Finally, the dynamic stress intensity factor equations for thick-walled cylinder containing a radial edge crack subjected to internal impulsive pressure are given by dynamic weight function method.

首先采用静态内压下的应力强度因子作为参考解，得到了带径向边裂纹厚壁圆筒的权函数；然后用振型函数方法推导无裂纹厚壁圆筒在冲击内压下的动应力响应，分析中将相应的弹性动力学方程解分为满足非齐次边界条件的准静态解和满足齐次边界条件的动态解的叠加，利用傅立叶-贝塞尔级数展开，推导出了厚壁圆筒内动应力的响应历程和分布规律；最后由动应力权函数方法导出带径向边裂纹厚壁筒在冲击内压下的动态应力强度因子计算公式。

According to this theory, the stress intensity factor around the crack-tip is a function of several variables, while Irwin's stress intensity factor K1 is a constant, therefore the factor K1 becomes a particular case of the generalized factor K1g.

作为钝角裂纹模型的K1g将在无限细的数学裂纹的尖点上退化为K1。广义应力强度因子的表达形式为风K1g＝ηK1，其中η是一个多变量函数，它是一个对于K1；的修正系数。在数学裂纹尖点上有η＝1。

Fatigue cracks develop in the shape of semi-ellipse, and the pattern of fatigue crack growth looks like headstand Y with the head pointing at the origin of the cracks.

疲劳裂纹源和裂纹扩展区部分的图像呈放射状的人字形条纹，人字纹指向裂源，其反向为裂纹的扩展方向。

Theobserved strain is 10~2 times as local point strain at the same observed stress.This indicates that macroscopical symmetrical rock is quasi-brittle materialwith microcosmic heterogeneousness and its macroscopical mechanicalbehavior is the results of reciprocity and magnification between microcosmiccharacteristic, not simple sum.(4) The degree of irregularity of strain increases with the number of cycle.But degree of irregularity of transverse strain fluctuates larger at the samecycle. Moreover degree of irregularity of transverse strain is larger than that ofaxial strain. This shows that deformation and failure of rock is process ofevolvement of small crack. Small crack evolves from even and out-of-orderstatus to heterogeneous and ordinal status.(5) Ultrasonic speed decreases with the number of cycle. The decreasecourse is such: Firstly, ultrasonic speed fluctuates in a steady scope in somecycles; And then ultrasonic speed quickly decreases to a certain more smallvalue; Afterwards in succedent cycles, ultrasonic speed fluctuates about thevalue. That is to say, ultrasonic speed fluctuates and decreases at intervals ofcycles. In deformation process of rock, quantitative change and qualitativechange of its small crack evolvement carry through crosswise.(6) Strength and modulus of rock decrease with exponential function asscale of specimens increases.

同一表观应力下，局部点应变与表观应变相差可达2个数量级，表明宏观上均匀的岩石是具有细观特征的准脆性材料，其宏观力学行为是细观特征相互作用、放大的综合结果，而不是简单的叠加；(4)岩样轴向应变不均匀程度和横向应变不均匀程度随循环次数的增加渐进增大，但是在同一个循环内，横向应变离散系数随应力的变化波动较大，且同一循环级别下，横向应变不均匀程度大于轴向应变不均匀程度，表明岩石内部微裂纹的演化是岩石变形破坏的本质特征，这一演化表现为微裂纹从均匀无序分布逐渐向非均匀有序发展；(5)随循环次数的增加，所有岩样内部超声波速会出现衰减，衰减过程表现为在某几次循环内超声波速在某一相对范围内波动，然后急剧减小到某一较小值，在随后的循环内，超声波速又会保持在这一较小值附近波动，即超声波速表现为波动和急剧减小间隔形式衰减，表明从宏观看来平稳的岩石变形过程，内部结构演化过程(微裂纹发展及其相互作用)却表现为均匀量变和突发质变不断交叉进行的现象；(6)岩石强度和弹性模量随尺度增大呈指数函数规律减小。

Scale, homogeneousness, direction of crack, length of a single crackand density of crack have influence on strength of specimens.

1试件尺度、均质度、裂纹方向、单一裂纹长度、裂纹密度对试件强度都有影响。

The order ofinfluence degree from bigness to smallness is homogeneousness, density ofcrack, direction of crack, length of a single crack and scale.

它们对强度的影响程度从大到小依次排列为：均质度，裂纹密度，裂纹方向，单一裂纹长度和试件尺度。

Finally three representative features are picked up, difference sum of the characteristic crack image projection in horizontal and vertical direction, as well as the pixel number of crack sub image.

基本思想是首先将二值化后的裂纹图像进行分块处理，得到一个特征裂纹图像，最后提取三个具有代表性的特征：特征图像在水平方向和垂直方向上的投影的差分累加和Ph，Pv以及裂纹子图像像素总数Num。

The proposed approach is verified by two cantilever beam experiments under ideal boundary conditions and uncertain end conditions, and the approach presented here is suitable for crack identification in engineering even if small frequency measuring errors exist.

对于理想边界条件下的裂纹参数识别，在测量频率存在小误差情况下，该方法仍能给出比较满意的结果，对于非完全固支边界条件下的裂纹参数识别，利用本文方法能得到比Narkis的方法更精确的裂纹位置识别结果。

The results of the tests indicate that the spots where the fatigue short cracks initiated are at the bottom surface of the circle indention and some disfigurement places in that surface. The propagation paths of the cracks are very complex and the decentralization of the obtained data is very severe due to the micro organism of the material. While the distribution of the short fatigue cracks exist self-regularity on their length, angle, density and expansion rate of the cracks, which are less affected by the outer factors.

试验中观察到短裂纹形状多为Z型，试验结果表明疲劳短裂纹往往萌生于试样缺口底部表面和缺口表面缺陷处，其扩展复杂，路径曲折，数据分散性大，强烈地受材料微观组织的影响，疲劳短裂纹在长度、角度、密度和扩展速率方面虽数据分散但具有自身的规律，受外部因素的影响较小。

The influence of indentor radius on the plastic deformation has been discussed and some important results are as follows:(1) The influence of the ratio of ceramic coating thickness to indentor radius on the failure of coating, plastic deformation of substrate and crack propagation are obvious.(2)The propagation of crack in ceramic coating is assumes to be of semi-elliptical shape under normal contact with a rigid sphere.(3)Fatigue life of ceramic coating is mainly decided by substrate and load, the lower substrate elastic moduli and load, the more cycles of fatigue.

分析了压头半径对塑性变形的影响，模拟结果表明；(1)陶瓷涂层厚度和压头半径之比对涂层失效、基体塑性变形及裂纹的形成有显著影响；(2)在刚性球压头静态挤压条件下，陶瓷涂层中的预制裂纹按照椭圆形裂纹规律扩展；(3)陶瓷涂层的疲劳寿命与基体和载荷有很大关系，基体弹性模量越小，疲劳寿命延长。

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。