裂纹

In this paper, a method is proposed to estimate the plastic zone size, by extending the Dugdale model to three dimensional (3D) crack problems and the crack opening displacement at the tip of a sptatial penny shaped crack by combining the Barenblatt Dugdale model with the principle of 3D J integral, then the relationship between J integral and COD is obtained.

将Dugdale模型推广到三维裂纹问题计算了圆盘状裂纹前缘塑性区尺寸，并结合断裂力学中的Barenblat－Dugdale裂纹模型和三维J－积分原理计算了圆盘状裂纹前缘张开位移，得到了J－积分与裂纹张开位移的关系。

It is shown that preventing welding hot cracking by mechanical methods can avoid the limitation of metallurgical methods and is very effective both for solidification cracking and for liquation cracking, thus has more freedom in choice of the parent metal and filler metal.

研究表明，采用力学方法防止焊接热裂纹可以避免冶金措施的局限性，对两类热裂纹（即焊缝凝固裂纹和近缝区液化裂纹）同样有效，因此，对焊丝成分和母材的选取有较大的自由度，是一种解决焊接热裂纹问题的重要的新途径。

The micro mechanism considers that the inclusion in material, called micro defect crack, is the nucleus of internal crack initiation, interaction, between the stress field of the micro defect crack tip as loading and strain field of crystal lattice caused by crystal point passim (as vacancies or interstitial atom, H, O, N et al), will trap the point passim, and cause the enrichment of point passim around the micro defect crack.

其中疲劳裂纹内部萌生的核心是材料中的第二相粒子、夹杂物或微空洞，称为微裂纹；而微裂纹的长大是材料中间歇原子或空位等点缺陷在微裂纹尖端富集沉淀的过程，微裂纹的长大速率受到点缺陷富集扩散速率和疲劳载荷的双重影响。

In order to know the character of them,the contact between them and the crack, and their forming process,we designed a special experiment- prefabricate crack in the shaped blank.

为了弄清此类异质颗粒的性质及其与裂纹之间的联系，以及具有该相同特征的裂纹组织的形成过程，特设计预制裂纹实验方案进行验证，通过试验研究，发现了异质颗粒的性质及其与裂纹之间的联系，判断出具有该相同特征的裂纹组织的形成过程，总结出了影响异质颗粒形成及大小的主要因素。

With the use of the dislocation method of complex potential function, this paper studies the interaction between the interface macrocrack and the interface or beneath-interface microcracks by the construction and numerical solution of singular integral equations .

采用复势函数的位错解方法，通过对奇异积分方程的建立和数值求解，研究了界面主裂纹同界面及基体微裂纹之间的干涉。结果表明远场载荷角ψ同Dunder's参数α对界面微裂纹及基体中水平微裂纹同主裂纹干涉的影响都很显著，而ψ对屏蔽区的影响则远小于α对其的影

The corrosion fatigue crack growth and near-threshold characteristcsof high tensile steel HT60 were investigated by using the compact specimens underexposure to synthetic sea water. The da/dN vs △K_ relation in air may be conser-vetivel estimated for that in sea water. In the high △K region with high stressratio, owing to the acceleration of crack growth promoted by stress-induced dissol-ution, the crack opening stress intensity factor K_ represents only the result ofcrack surface in contact with corrosion products, so as to give an overestimation ofK_ at crack tip.

对高拉力钢HT60的腐蚀疲劳裂纹扩展特性和门槛值区域特性，采用紧凑拉伸试件在人工海水中进行了实验和研究，结果表明：在空气中的da/dN与ΔK_关系可以作为在海水中的da/dN与ΔK关系的一个偏保守的预测；在高应力比的高ΔK区域，由于应力诱起溶解促进了裂纹扩展的加速；该裂纹开口应力强度因子K_仅反映了裂纹表面同腐蚀生成物接触的结果，从而导致了K_在裂纹尖端的偏大的估计结果。

Secondly, the paper carries on the destruction processes and the stress distribution situation numerical simulation of the concrete three point bending specimen with bias crack under static load function,, and analyze specimen crack expansion and the destruction mechanism, obtain the reason that the crack expanding flectional way is because the material nonuniformity, in the same time, from the specimen destruction process chart we can see that the crack bias degree has some influence on the crack expansion way.

其次论文对含偏置裂纹的混凝土三点弯曲试件在静态载荷作用下的破坏过程和应力分布情况进行了数值模拟，并对试件的裂纹扩展和破坏机理进行了分析，得出裂纹扩展的曲折性是由于材料不均匀性所引起的，同时从试件的破坏过程图中可以看出，裂纹的偏置程度对裂纹的扩展路径有一定的影响。

Although the EPRI give a set of the approximate engineering solution method, actually the crack of parts in engineering project mostly presents inner 3D effect. If using 2D elastic-plastic or 3D elastic analysis, the result can't be precise. Because these methods have neglected the reassignation of the stress and strain which happened at nearly the top of cracks, carrying on 3D elastic-plastic analysis and J-integral calculation become the foundational work to study the expander and safety assessment of the pressure vessel cracks.

虽然EPRI给出了一套近似的工程解法，但实际上工程中构件的裂纹大多呈现内在的三维效应，若使用二维弹塑性或三维弹性分析必然不够精确，因为对裂纹的&等效&二维表达忽视了发生在靠近裂纹端部的应力和应变的再分配，所以对压力容器裂纹进行三维弹塑性分析及其J积分是研究压力容器裂纹扩展和安全评定的基础工作之一。

The microfracturing process of Jinping marble specimen in Sichuan province under uniaxial compression is recorded by using the testing scheme. Quantitatively investigated the propagation and coalescent of cracks at meso-scale with digital technology, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, are obtained from binary images after segmentation. The failure mechanism of specimen under uniaxial compression with the quantitative information is studied from macro/micro scopic perspective. The result shows that during the damage of the specimen the distribution of microcracks in the whole specimen are still subjected to exponential distribution with some microcracks concentrated in certain regions.

应用于四川锦屏大理岩预制裂纹试样中进行单轴压缩破坏全程的数字化试验，对微裂纹的萌生、生长及贯通过程进行数字化定量分析，得到试样在受荷过程中微裂纹的面积、方位角、长度、宽度和周长基本几何数据，从宏细观角度描述了岩石试样单轴压缩过程中的破坏机制，并分析得出试样单轴受压破坏过程中虽然微裂纹在某些区域集中，但在整个试样中微裂纹的统计分布依然是服从某一指数分布的这一结论。

Under different combustion pressuring rates of the solid motor, the relations among the convecting combustion flow characteristics, especial the pattern of flame spreading, and the variation of stress intensity factor at the crack tip are discussed in detail.

文中详细描述了在固体火箭发动机燃烧室环境中，药柱裂纹对流燃烧流场特性和固相裂纹体变形特性；燃烧室增压率对裂纹中火焰传播方式的影响；燃烧室增压率、燃烧室平衡压力的设计值、药柱裂纹径向长度对固相裂纹尖端应力强度因子、燃烧室压力的影响。

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。