Study on the friction interface evolution during rotary friction welding of tube

In this study, evolution characteristics of the friction interface during rotary friction welding of tube were investigated. The friction interface that obtained at different welding stage were observed by confocal laser scanning microscopy. The results show that the friction interface transforms from sliding friction state to visco-plastic deformation state when the welding torque reaches the peak value. In addition, based on the thermodynamic framework extracted from the maximum entropy production principle, an analytical model for transition criterion from sliding friction to visco-plastic deformation was established. The model was verified by the corresponding experimental results of eight alloys, which indicated that the accuracy and generality of the model is satisfactory.     

在处理三废时应注意新的污染

人类文明的增长,对环境的要求亦相应增长,同时,对于生态和环境的破坏亦随之增加。所以,我们治理环境,需从全球的平衡来考虑三废的治理,依靠科研,依靠政策的扶持,用建立优化的人工生态系统来保护环境。     

Finite‐deformation irreversible cohesive elements for three‐dimensional crack‐propagation analysis

We develop a three‐dimensional finite‐deformation cohesive element and a class of irreversible cohesive laws which enable the accurate and efficient tracking of dynamically growing cracks. The cohesive element governs the separation of the crack flanks in accordance with an irreversible cohesive law, eventually leading to the formation of free surfaces, and is compatible with a conventional finite element discretization of the bulk material. The versatility and predictive ability of the method is demonstrated through the simulation of a drop‐weight dynamic fracture test similar to those reported by Zehnder and Rosakis. The ability of the method to approximate the experimentally observed crack‐tip trajectory is particularly noteworthy. © 1999 John Wiley & Sons, Ltd.     

“三高井”试油测试工艺探讨

总结了三高井测试的设计原则、常用的试油测试工艺及工序,分析了试油施工中出现的意外情况,归纳出三高油气井试油施工的注意事项。     

表面织构形状对牙轮钻头轴承摩擦学性能影响的实验研究

牙轮钻头滑动轴承作为钻头破岩过程中传递载荷的关键部件,在低速重载的钻井过程中易发生黏着磨损失效。为改善牙轮钻头滑动轴承的耐磨性能,利用纳秒激光雕刻技术,在牙轮钻头滑动轴承轴颈表面加工了面积比为10%、深度为20μm的圆形、矩形、三角形及复合织构;基于赫兹相似理论,设计近似模拟钻头轴承工况的环-块配对副单元实验方案,并在UMT摩擦试验机上开展织构形状对钻头滑动轴承摩擦副摩擦因数、磨损量、温升变化和微观形貌影响规律的实验研究。结果表明:仿生织构的形状及布置方式对减摩和耐磨效果影响极大,其中圆形、矩形织构的减摩和耐磨性能最优,其次为三角形织构,而复合织构反而增大了摩擦因数及磨损量;单一织构对试件磨损量及温升的影响不大,而复合织构在增加摩擦的同时温度有明显升高,不利于井下高温环境下延长牙轮钻头寿命。     

磁悬浮控制力矩陀螺高速转子的高精度位置控制

在受到陀螺效应、动框架效应等影响后产生的磁力非线性问题是磁悬浮控制力矩陀螺(MSCMG)高速转子位置精度下降的主要因素。为解决以上问题,提高转子位置精度,本文分析了转子所受磁力的特性,建立了转子系统非线性动力学模型,提出了神经网络滑模控制方法。设计滑模控制律,采用径向基函数神经网络逼近控制律中的非线性模型,自适应算法根据误差在线调整神经网络的权值,同时可以保证整个系统的稳定性。仿真和实验结果表明,所提出方法的转子位置精度达到99%,稳态误差为0.000 2 mm。神经网络滑模控制可以实现MSCMG转子系统的高精度位置控制。     

钢结构桥梁高空滑移操作平台

本文研究制作了一种高空滑移操作平台,为钢结构桥梁悬挑部分的高栓、焊接以及涂装等作业提供了一个安全、舒适的施工平台,极大的提高了高空悬空作业的安全系数。此操作平台制作简单,滑移方便,在解决施工难题的同时也节约了工程成本,加快了工程进度。     

滑动测微计在某发电厂桩基内力测试中的应用

结合某火力发电厂桩基试验的工程实例，详细介绍了滑动测微计在桩身内力测试中的应用原理和方法，计算了该工程试桩的极限侧摩阻力和端阻力以及不同土层的侧摩阻力系数，对该工程的桩基优化设计及工程桩检测具有较大的参考价值。     

弹簧限位抗震支座在五棵松文化体育中心体育馆大跨钢屋架设计中的应用

五棵松文化体育中心体育馆为2008北京奥运会篮球馆,钢结构屋架跨度为122.3m,采用了非等高(6.3~9.3m)双向正交钢桁架体系。桁架结构支承在周边20根钢筋混凝土柱上。除与四角柱为双向固定铰接外,钢屋架与其它柱在平行于桁架方向采用了有弹簧限位的滑动支座,垂直于桁架方向为固定铰接。滑动支座有效地控制了屋架传给承重柱的推力,尤其在地震作用下。在考虑竖向荷载组合、多遇地震荷载组合和设防地震荷载组合的情况下,均能满足承载力极限状态和正常使用极限状态要求。     

Friction behavior of Al-Cu-Fe-B polycrystalline quasicrystals

Dry sliding friction between the polycrystalline Al59Cu25.5Fe12.5B3 quasicrystals(QCs) and coating of the diamond-like carbon(DLC) was carried out by self-made tribometer under different conditions. The influences of four parameters(temperature, sliding velocity, applied load, atmosphere) on friction of quasicrystal surface were studied. Microstructure of quasicrystal, morphology of worn surface, and wear debris were observed by scanning e-lectron microscope(SEM). The results show that for QCs, the friction coefficient and the roughness of worn surface is influenced by the parameters, especially greatly by the temperature. With increasing the applied load and sliding velocity, the friction coefficient decreases. The dominant wear mechanism at 350℃ is delamination for QCs. The cracks forms on the worn surface during friction. Moreover, phase transformation is not observed on worn surface of QCs at 350℃.