疲劳

The thermal fatigue behavior of the cast hot-work die steel and H13 steel was also contrasted.

结果表明，铸造热作模具钢的热疲劳属高周热疲劳，其热疲劳性能取决于钢的热强性和热稳定性。

Thermal fatigue property of the cast hot-work die steels with different V/C was investigated with the self-restricting test method.

采用自约束热疲劳试验方法，研究了不同V/C对铸造热作模具钢热疲劳性能的影响，并对比研究了铸造热作模具钢和H13钢的热疲劳性能。

During the prior fatigue life, fatigue damage induces a very small stiffness reduction value that always may be neglected. In the final fatigue life, the stiffness reduction evidently minishes following the power function.

在疲劳寿命前期，疲劳损伤对复合材料层板产生的刚度降变化很小，可忽略不计；在疲劳寿命后期，刚度降则按幂函数变化显著减小。

Through above numerical analysis of the TiN coating/substrate system, some typical rules about the fatigue failure are found:(1) the fatigue damage of a coating/substrate system appears first on the interface, then expands along the interface and to the substrate, and finally causes the coatings broken and spalled;(2) under the cyclic loadings of tangential sliding and radial extrusion, the equivalent plastic damage on the interface is mainly generated by the shear stress and the accumulated plastic contributed by the increments of shear stress. Thus the change of the shear stress is the main factor for the contact fatigue damages of coating/substrate system;(3) the frictional coefficient, external loading and coating thickness have some influence on the carrying capacity and contact fatigue life for a coating/substrate system.

通过对TiN涂层／基体系统的数值模拟分析，得到了涂层／基体系统疲劳失效的一些典型规律：(1)、涂层基体的初始损伤首先出现在交界面处，然后沿界面并向基体中扩展，最后导致涂层断裂而发生剥落失效；(2)、在切向滑动和径向挤压循环载荷作用下，交界面处的塑性损伤主要是由剪应力τ产生，塑性累积也是由于△τ的变化引起，说明循环过程中剪应力变化是影响涂层接触疲劳破坏的主要因素；(3)、材料摩擦系数、外界载荷大小以及涂层厚度都对涂层／基体系统的承载能力以及疲劳寿命都有一定影响。

Considering to the fatigue calendar characteristics of materials, the sequence effects of loading spectrum and the mechanical behavior of cyclic hardening/softening of metals, the cumulative fatigue damage is proved to have character of Markov process. Also, the distribution of the cumulative fatigue damage and its critical value is deduced to vary with the pre-exposure calendar time of materials.

考虑载荷次序效应、材料循环硬化/软化效应及材料的大气环境腐蚀老化效应，论证了疲劳累积损伤随机过程的Markov性，及疲劳累积损伤的正态分布特性，同时证明了临界累积损伤的统计特性随日历时间的变化关系，在此基础上建立了一新的全动态疲劳累积损伤统计干涉模型。

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。

By means of self-designed test method ,thermal-fatigue resistance and influence factor for surfacing metal of three self-produced flux-cored wires and one solid wire for roller hardfacing were studied deeply.The mechanisms of thermal-fatigue crack initiation and extension were investigated .

通过设计的热疲劳试验方法，对三种自制药芯焊丝和一种国产堆焊轧辊用实心焊丝的耐热疲劳性能及其影响因素进行了深入研究，同时对堆焊金属中热疲劳裂纹形成以及扩展机理做了进一步探讨。

In practical application item, UIC515 Code is firstly applied for analyzing the complete welded frame by finite element method to get the area with bigger nominal stress and lower fatigue behavior, and then study the hot spot stress fatigue strength evaluation approach of the typical fillet ring joint at the connection of tubular transom and side frame, the plate to plate end weld between side frame web plate and anti-yaw damper hold and the non-close ring end weld at the connection of braking unit hold and tubular transom.

在热点应力疲劳评估时，首先对焊接构架中的环向角焊缝、板间端焊缝以及非闭合环向端焊缝进行简化，得出了相应的几何应力集中系数和热点应力疲劳极限，为热点应力疲劳评估提供了依据。

In the light of the shortcomings of the traditional method for predicting the fatigue life of coiled tubing, a new method for the reliability analysis of coiled tubing is offered, that is, normalizing the fatigue test data of coiled tubing with different materials and stress states by introducing a compound random variable X=NS2 based on low cycle fatigue curves.

预测连续油管疲劳寿命传统方法是将许多试样在不同应力水平的循环载荷作用下进行试验直至失效，从而作出S－N曲线，供工程参考，这样不仅费用高，且模拟实际应力条件也较困难。为此，根据低周疲劳曲线，通过引入复合随机变量X=NS2，对不同材料和应力水平下的连续油管疲劳实验数据进行了归一化处理。

Since historical times,England ,where the early inhabitants were Celts, has been conquered three times .

从有历史以来，英国，在此地早期居住的是凯尔特人，已经被征服了三次。

Bluetooth OBEX File Transfer Enables the sending and receiving of files on your phone via Bluetooth.

蓝牙OBEX文件移动允许经过蓝牙传送和接受文件。。。。