断裂的

Based on the foregoing analysis, the critical condition of realizing ductile/brittle transform is confirmed, and then, the model of ductile grinding of engineering ceramic is built.

以陶瓷材料压痕断裂力学、线性断裂力学和微观断裂物理学为理论基础，系统的分析和讨论了磨削加工过程中微裂纹的产生机理及其影响因素，建立了裂纹分布模型，并根据位错产生微裂纹机制，对磨削过程微裂纹的形成采用位错塞积模型来描述，从能量平衡的角度，讨论位错裂纹的稳定性与磨削应力的关系，确定了材料脆性去除和塑性去除转换的临界条件，最终建立以此为基础的工程陶瓷材料延性域去除模型。

For the composites with a low content of TiC particle, the rupture manner was mainly the nucleation of cavity and following ductility splitting fracture. But for the composites with a high content of TiC particle, the cracking and decohesion of TiC particles were the main rupture mechanism. For the composite containing a middle TiC content, the rupture mechanism consisted of the above two styles, but the former was the dominating mechanism and the later was the subordinate mechanism.

对TiC体积分数较低的钢基复合材料，拉伸过程中TiC颗粒界面上的孔洞形核及随后塑性撕开机制是其断裂失效的主要机制；对TiC体积分数较高的钢基复合材料，拉伸过程中TiC颗粒的开裂及脱落是其断裂失效的主要机制：对TiC体积分数介于上述两者之间的钢基复合材料，拉伸过程中TiC颗粒界面上的孔洞形核及随后塑性撕开机制在其断裂失效过程中占主要地位，而TiC颗粒的开裂及脱落占次要地位。

In order to study the fatigue of pressure vessel commonly encountered problem in engineering with large destructibility , based on the theory of fracture mechanics , the pressure vessel existing original crack was equivalent to the problem of infinite flat with center crack .

为了分析工程中常见的破坏性极大的压力容器疲劳问题，基于断裂力学理论将存在初始裂纹的压力容器等效为无穷远处作用均匀拉应力的含中心裂纹无限大板问题，解出表面半椭圆裂纹和穿透裂纹的应力强度因子；利用断裂判据得到裂纹的临界断裂尺寸；采用Paris表达式对裂纹扩展速率进行描述，推导出初始裂纹在不同裂纹尺寸和形式下的裂纹疲劳扩展寿命。

The deformation mechanism is mainly the single-slip and cross-ship, the fracture mechanism is mainly the congregation of transgranular micro-hole, and large uniform deformation occurred before tough fracture, and therefore, the ability of plastic deformation and the mechanical properties of the material were remarkably improved. These fully indicate that the new melt-treatment developed in this work is an effective and advanced technique, and further testify that the improvement of metallurgical quality of the material is the key to enhance its mechanical properties, especially its plastic deformation performance. The results of tensile and compression tests at elevated temperature also indicate that the suitable hot-working temperature range is 400～450℃. 4. A steady-state plastic flow exists during the plastic deformation of the aluminum sheet used for pressure can at elevated temperature. A hyperbolic sine relationship can be satisfied between the steady-state flow stress and strain rate by introducing an Arrhenius term which involves some thermal activation parameters, i.

压力罐用铝材中的主要冶金缺陷为Al〓O〓夹杂物、气孔及富Fe杂质相；高效熔体处理显著改善了材料的冶金缺陷的存在形态，使含杂量明显减少、夹杂物尺寸变细小且分布均匀，富Fe杂质相变为细小、分布均匀的团球状或短棒状的复杂化合物，同时也明显细化了结晶组织；此外，由于高效熔体处理有效地减少了材料中裂纹萌生源数量，因而改变了材料的塑性变形微观过程及断裂方式，主要以单滑移和交滑移进行塑性变形，断裂方式为穿晶微孔聚集型，韧性断裂前产生了大量的均匀变形，不易出现变形失稳，从而显著提高了罐用铝材的塑变能力和力学性能。

Since Watson and Crick have brought forward the model of DNA helix structure and explain about it's reproduce mechanism in molecule level, research work concerning DNA has been continuously lucubrated. However, whether translating inheritance information and rebuilding DNA molecule via menstruating DNA sequence, or to date the most compelling gene project, chromosome protract et. al, there all need a sort of molecule scissors cleaving DNA, DNA cleavage reagent. At present, tool enzyme of cleaving DNA is mostly DNA restriction enzymes founded in 70 years, which only cleave DNA at specific 4-8 base pair sequences that are usually palindromic, so this restricts the at very fast speed developing of gene technology at certain extent.

自从Watson和Crick提出DNA的双螺旋结构并对其复制机制在分子水平上进行解释后，使得对DNA的研究不断深入，但无论是通过测定DNA的序列来破译遗传信息、改造DNA分子，还是目前最令人关注的基因工程、染色体绘制等，都需要一种断裂DNA分子的&剪刀&——DNA断裂试剂，目前断裂DNA的工具酶主要是上个世纪70年代发现的DNA限制性内切酶，但所知的Ⅱ型限制性内切酶的DNA序列识别长度较短（约为4～8个碱基对），而且一般要求回文结构，这就给飞速发展的基因工程技术带来一定的限制。

In designing capsuling self-repair ing smart composites,the key factor is to control the fracture features of basement material and capsuling material,and have them primely matched.

微胶囊型自修复复合材料设计的关键是基体材料和胶囊壳体材料的断裂韧性要在一定的范围内，使得基体材料的断裂特性和胶囊壳体材料的断裂特性达到最佳的匹配，这样才能保证自修复过程的实现。

Combined with the macro-morphology appearance analysis and working conditions of failure casing, the paper reached a conclusion that it is due to the impact and friction which come from the drill tools made the fatigue cracks formation on the casing thread root, and eventually leading to casing rupture failure, the material defects in failure casing accelerated crack initiation and growth.

摘 要：某井在钻井作业过程中，发生了上层Φ244.5 mm技术套管断裂失效事故，为了分析事故原因，对失效套管材料的化学成分、金相组织和力学性能进行了检测分析，结合套管失效形貌的宏观分析和套管使用过程中的现场工况分析，得出了套管螺纹发生断裂失效的原因是钻具对套管的撞击、摩擦，使套管螺纹根部产生疲劳裂纹，最终导致套管断裂失效，失效套管的材料缺陷加速了裂纹的萌生和扩展。

It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than that in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.

失效分析表明，钻杆属于早期疲劳断裂，断裂主要原因是在空气钻井过程中钻具受到的震动载荷远大于钻井液钻井过程中的震动载荷，在交变的震动载荷作用下，钻具容易产生疲劳裂纹；由于现有的井口检测仪表不能精确及时反映钻杆刺穿之后产生的泵压变化，无法及时采取预防措施，疲劳裂纹不断扩展，最终导致了钻杆断裂失效。

It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.

失效分析表明，钻杆属于早期疲劳断裂，断裂主要原因是在空气钻井过程中钻具受到的震动载荷远大于钻井液钻井过程中的震动载荷，在交变的震动载荷作用下，钻具容易产生疲劳裂纹；由于现有的井口检测仪表不能精确及时反映钻杆刺穿之后产生的泵压变化，无法及时采取预防措施，疲劳裂纹不断扩展，最终导致了钻杆断裂失效。

As an example of application, the study on small scale shear failure of Al-Zn-Mg-Cu plate under complicated strain and stress states, especially within the plastic zone ahead of a pre-crack, would promote our understanding of the fracture mechanism, of the shielding effect caused by cracking path deflection, and of the mechanism of fracture toughness anisotropy of textured high strength aluminium alloys.

作为一个应用实例，本文关于Al-Zn-Mg-Cu厚板在复杂应力应变状态下的小尺度剪切失效机制的研究，对于了解工业高强变形铝合金的断裂过程、了解裂纹扩展途径偏斜所引起的shielding效应、了解断裂特征和断裂韧度的各向异性等实际问题也是很有启发的。并已被Materi-als Science and Technology认为是&an interesting piece of work containingsome original idea s&。

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。