微裂纹

The effects of pre-existing macrostructures, such as joint, bedding plane on AE occurrence rate and b-value are the same as that of microcracks. AE spatial distribution is controlled by the pre-existing macrostructures and the macrostructure clustered by AE events usually controls the coming final fracture.

宏观结构的存在对声发射率和b值的影响与微裂纹相同，而且宏观结构对声发射的空间分布具有控制作用，声发射丛集的宏观构造通常控制著未来的主破裂。

There are no fine cracks in the interface,and the bonding states between conjoint layers are ideal.

层间界面结合良好，不存在微裂纹，从而具有较好的力学性能。

For rock samples under uniaxial compression test, its failure forms include friction slippage, self-similar propagation and crankle expansion of microcracks.

对于单轴压缩的岩石试件，其破坏型式主要是微裂纹的摩擦滑移、自相似平面扩展和弯折扩展。

Thermal oxidation treatment can increase the surface hardness and elastic modulus significantly and reduce the E /H ratio of the TC4, which indicate the treatment can enhance the wear resistance of TC4 alloy. Long time treatment can increase the thickness of the oxide layer, but the outside layer is apt to desquamate during the scratching. The oxide layer closing to substrate has better bonding properties, but microcrack forms as a result of high stress loading, which lead the layer to flake off completely.

长时间的高温氧化可以增加氧化层的厚度，但在划擦过程中氧化层发生两次脱落，表明氧化层由外表层和次外层组成，外层结合力差，易发生一次脆性剥落，内层与基体的结合强度较高，但在较大载荷作用下会产生微裂纹，导致氧化层的二次剥落。

Glassiness SiO2 layer is formed on the surface of coatings after exposure long time,which can isolation of oxygen and fills in interstice on the surface of coatings.

采用加入其他元素的方法使硅化铌改性可达到减少穿透硅化铌涂层微裂纹的生成和降低铌基材氧化速度的目的，但使用温度一般不超过1 300℃[1~3]。

On one hand, the grain boundaries are the sites of microcrack nucleation, microcracks first occur at grain boundary zone, whose propagation type depends on lamellar orientation of both side of grain boundary.

一方面，微裂纹首先萌发于晶界区，其扩展方式取决于晶界两侧片层的取向。

Key words: sandstone; microcracks; wave velocity; mechanical properties

关键词］砂岩，微裂纹，超声波速度，力学性质

Therefore, it is important to discover the existence of the microcrack in time before the marine accidents occur.

因此，在发生海损事故前，及时发现各构件存在的微裂纹是十分重要的。

It is put forward that microcrack in the material is the major reason for breaking.

提出材料表面的微裂纹是材料脆性断裂的根本原因。

A nonequilibrium statistical description of microcrack growth dynamic process has been given.

二、建立了微裂纹长大动力学过程的非平衡统计描述。

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。