硬质合金在牙轮钻头滑动轴承上的应用研究          下载免费PDF全文

王镇泉  巩立根  谭春飞  翁行芳 《探矿工程》1997,(2):31-34

在分析牙轮钻头轴承摩擦损机理的基础上，提出改进其轴承摩擦表面材料是提高其寿命的有效途径，通过对硬质合金的力学性能和摩擦性质的分析，论证了硬质合金可以用于齿轮钻头滑动轴承摩擦表面，并提出了硬质合金脆性的解决方法。  相似文献   

岩体节理形貌的分形维数与摩擦角的关系研究   总被引：1，自引：0，他引：1  

陈乃明 《岩土力学》1996,17(3):54-58

在土木工程设计和施工中，岩体节理的摩角是一个重要参数，该值的获取既费时又费力。本文首先简要介绍节理形貌的描述方法和分形几何理论，然后将分形理论引人岩体节理摩擦角的研究中，得出了用分形维数表示摩擦角的经验公式。关键词  相似文献   

喷,锚,网结构在基坑支护中的应用   总被引：5，自引：1，他引：5  

傅治栋 《岩土力学》1996,17(3):65-69

高层建筑地下室基坑开挖时，边坡需要支护。本文就应用喷、锚、网结构进行边坡支护的作用机理、计算方法、施工中应注意的几个问题作了介绍和讨论。  相似文献   

Pore-Pressure Rise, Frictional Strength, and Fault Slip: One-Dimensional Interaction Models     

Tien-Chang Lee 《Geophysical Journal International》1996,125(2):371-384

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Multiple‐tuned liquid column dampers for torsional vibration control of structures: theoretical investigation     

Y. L. Xu  K. M. Shum 《地震工程与结构动力学》2003,32(2):309-328

This paper presents a theoretical investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). The analytical model is first developed for torsional vibration of a structure with an MTLCD under either harmonic excitation or white noise excitation. The experimental results are then used to verify the analytical model for coupled MTLCD‐structure systems under harmonic excitation. The performance of an MTLCD and its beneficial parameters for achieving the maximum torsional response reduction to white noise excitation are finally investigated through an extensive parametric study in terms of the distance from the centre line of the MTLCD to the rotational axis of the structure, the ratio of the horizontal length to the total length of liquid column, frequency bandwidth, head‐loss coefficient, the number of TLCD units in an MTLCD, frequency‐turning ratio and the spectral level of excitation moment. The results show that there is an optimal head‐loss coefficient and an optimal frequency bandwidth for an MTLCD to achieve the maximum torsional response reduction. It is also demonstrated that the sensitivity of an optimized MTLCD to the frequency‐tuning ratio is less than that of an optimized STLCD, and it can be further improved by increasing the bandwidth but at the cost of less torsional vibration reduction. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

非对称结构扭转振动多重调谐质量阻尼器(MTMD)控制的最优位置   总被引：1，自引：1，他引：1  

李春祥  韩传峰 《地震工程与工程振动》2003,23(6):149-155

研究了非对称结构扭转振动多重调谐质量阻尼器(MTMD)控制的最优位置。本文采用的MTMD具有相同的刚度、阻尼，但质量不同。基于导出的设置MTMD时非对称结构扭转角位移传递函数，建立了扭转角位移动力放大系数解析式。MTMD最优参数的评价准则定义为：非对称结构最大扭转角位移动力放大系数的最小值的最小化。MTMD的有效性评价准则定义为：非对称结构最大扭转角位移动力放大系数的最小值的最小化与未设置MTMD时非对称结构最大扭转角位移动力放大系数的比值。基于定义的评价准则，研究了非对称结构的标准化偏心系数(NER)和扭转对侧向频率比(TTFR)对不同位置MTMD最优参数和有效性的影响。  相似文献   

钻孔扩底灌注桩的设计与检测          下载免费PDF全文

韩建强  宋庆东  杨明 《地质与勘探》2003,39(4):90-91,94

结合钻孔扩底灌注桩在某高层建筑物基础中的成功应用,对钻孔扩底灌注桩的成桩原理进行了有关的阐述,认为扩底钻头的扩张角α≤25°为宜,且扩底高度范围内岩石层的饱和单轴抗压强度标准值一般不大于6MPa;同时在单桩竖向承载力的设计计算时,要求对桩身侧阻力与桩底端阻力进行相应修正。为确保钻孔扩底灌注桩桩端扩大头的施工质量,根据其自身特点,提出采用传统的钻孔取芯法进行检测,并针对工程应用情况进行了定性评价。  相似文献   

Analytical model of structures with frictional pendulum isolators     

Jos L. Almazn  Juan C. De la Llera 《地震工程与结构动力学》2002,31(2):305-332

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Intelligent technology-based control of motion and vibration using MR dampers   总被引：1，自引：0，他引：1  

周丽  张志成  苏磐石 《地震工程与工程振动(英文版)》2002,1(1):100-110

Due to their intrinsically nonlinear characteristics, development of control strategies that are implementable and can fully utilize the capabilities of semiactive control devices is an important and challenging task. In this study, two control strategies are proposed for protecting buildings against dynamic hazards, such as severe earthquakes and strong winds, using one of the most promising semiactive control devices, the magnetorheological (MR) damper. The first control strategy is implemented by introducing an inverse neural network (NN) model of the MR damper. These NN models provide direct estimation of the voltage that is required to produce a target control force calculated from some optimal control algorithms. The major objective of this research is to provide an effective means for implementation of the MR damper with existing control algorithms. The second control strategy involves the design of a fuzzy controller and an adaptation law. The control objective is to minimize the difference between some desirable responses and the response of the combined system by adaptively adjusting the MR damper. The use of the adaptation law eliminates the need to acquire characteristics of the combined system in advance. Because the control strategy based on the combination of the fuzzy controller and the adaptation law doesn’t require a prior knowledge of the combined building-damper system, this approach provides a robust control strategy that can be used to protect nonlinear or uncertain structures subjected to random loads. Supported by: Hong Kong Research Grant Council Competitive Earmarked Research Grant HKUST 6218 / 99E and by the National Science Foundation under grant CMS 99-00234.  相似文献   

非线性粘滞阻尼器消能结构减振效果分析   总被引：5，自引：1，他引：4  

蒋通  贺磊 《世界地震工程》2005,21(2):57-63

应用并完善了非线性粘滞阻尼器消能结构地震反应预测的反应谱方法,通过与时程分析计算结果对比证明了方法的可行性。利用本方法研究了支撑刚度及阻尼器参数对非线性粘滞阻尼器减振效果的影响。通过数值分析,给出了位移降低率达到最佳时支撑刚度取值的建议式。提出了为保证剪力降低率不大于1时非线性粘滞阻尼器参数的控制方法。  相似文献