基于声发射技术的内燃机润滑油粘度状态非介入式检测研究

润滑油的粘度变化是影响缸套-活塞环间摩擦润滑状态的主要因素之一。为了实现润滑油粘度的非介入式检测,本文通过声发射技术对缸套-活塞环间摩擦润滑状态进行了检测分析,采用小波变换、阈值降噪等方法实现信号的处理,得到了润滑油粘度与摩擦所产生声发射信号的近似关系。结果表明：随着转速的升高,声发射信号的电压幅值明显增加,缸内摩擦明显增大;随着润滑油温度的上升,粘度减小,声发射电压信号幅值逐渐减小,缸内摩擦相应地减小,且具有较好的线性相关性,为润滑油的状态检测与及时更换提供了技术手段,同时证明了声发射技术作为一种缸套-活塞环摩擦研究手段的有效性。     

液黏传动双圆弧油槽摩擦副油膜剪切转矩研究

双圆弧油槽摩擦副广泛应用于液黏传动,为了研究油槽结构参数对油膜剪切转矩的影响,对摩擦副间流体的流动特性进行数值模拟,得到了油膜剪切转矩.建立了集流场参数化建模(CAD)、数值模拟(CFX)、试验设计方法(DOE)及响应曲面法(RSM)为一体的油槽参数影响分析平台,分析了油槽深度、油槽宽度和油槽数目对油膜剪切转矩的影响并建立了近似响应曲面模型.搭建转矩性能试验台进行试验验证,结果表明:油膜剪切转矩随着油槽深度、宽度和数目的增大均减小,而油槽宽度对转矩的影响最大,油槽深度影响次之,油槽数目影响最小.通过理论和试验研究,应用CFX数值模拟和建立摩擦副油槽参数影响分析平台实现了CAD、CFX、DOE及RSM等技术的高度融合,可以准确地分析摩擦副油槽参数对油膜剪切转矩的影响.     

Molecular dynamics simulations of atomic-scale friction in diamond-silver sliding system

Molecular dynamics simulations have been performed to explore the atomic-scale sliding friction, especially the stick-slip friction, in a system consisting of a diamond slider and a silver substrate. The mechanisms of the stick-slip behavior are investigated by considering sliding speeds between 10 m/s and 200 m/s.The analyses of the shear distance between the upmost layer and the downmost layer and displacements of a column of atoms in the slider show that shearing deformation of the slider is the main cause of the stick-slip phenomenon. Our simulations also present that a commensurate fit between the two contact surfaces is unimportant for the stick-slip friction.     

基于LuGre模型的电液伺服马达摩擦力矩补偿

针对大体积飞行器仿真试验时的重力偏载情况,设计并制造了一种仿真转台用中空式电液伺服马达。对影响其超低速跟踪性能的摩擦力矩进行了分析,建立了大摩擦力矩条件下的中空马达数学模型。设计了一种基于LuGre模型的自适应摩擦力矩补偿控制器。为验证该控制器的有效性,进行了不同输入下的数值仿真及试验研究。结果表明与传统的PID控制相比,基于LuGre模型的自适应摩擦力矩补偿控制能够更好地实现马达的低速性能。     

非饱和土基质吸力对抗剪强度参数影响的探讨

分析了前人提出非饱和土抗剪强度理论存在的局限性,通过试验研究和理论分析,验证了非饱和挤密黄土吸力对抗剪强度影响的内摩擦角值并非一个常数,而是随吸力的增大而减小,并得出吸力与内摩擦角之间的非线性函数关系,为研究非饱和土强度问题提供了理论依据．     

偏心压紧装置的力学设计

通过对偏心央紧装置在工作过程中存在着对试件表面造成一定的摩擦拉伤这一问题的分析,对机构进行了改进设计,较好地解决了试件表面摩擦拉伤这一难题,同时也提高偏心央紧装置的增力倍率,减轻了劳动强度,提高了实验数据的精确度．     

灌注桩后注浆技术分析

注浆是岩土工程中一门专业性很强的学术分支,用注浆处理各种岩土工程问题,已成为常用的方法。桩基后注浆技术能够提高桩承载力,减少桩沉降量以及提高桩顶回弹量,文章针对汾河地区进行桩基在注浆与未注浆的条件下,对比静载试验和桩侧摩阻力测试结果,并总结出桩基后注浆技术相关结论与经验。     

多自由度电流变阻尼隔震结构的数值分析

采用电流变智能隔震装置对多自由度结构进行了基础隔震控制.给出了电流变智能隔震装置的基本构造,提出了隔震装置的恢复力模型.根据摩擦结构运动机理,分析了隔震结构的动力特性,给出了隔震结构各阶段的运动方程及其判别准则,编制了结构非线性动力分析程序.对多自由度隔震结构进行了动力时程分析,分别采用3种恢复力模型的隔震装置对结构进行控制.结果表明,采用电流变智能隔震装置对结构进行控制可以有效地限制隔震层的位移.此外,拟限位型隔震装置还可以有效降低结构加速度,拟摩擦装置对结构加速度有所增加.     

Model tests on anomalous low friction and pendulum-type wave phenomena

The anomalous low friction (ALF) and pendulum-type wave (μwave) phenomena were two typical,nonlinear,geo-mechanical,and dynamic responses in deep-block rock mass discovered from in situ observations,which occurred from the movement of the geo-blocks under the impact of external pulses,such as deep confined explosion,earthquake,and rock bursts.With the aim to confirm the existence of the above two phenomena and study the variation laws of them experimentally,laboratory tests on the granite and cement mortar continuum and blocks models were conducted on the self-independently developed multipurpose testing system,respectively.The ALF phenomenon was realized under two loading schemes,the blocks model and working block were acted upon by the joint action of vertical impact and horizontal static force as well as the joint action of both vertical and horizontal impacts with different time intervals.It revealed that the discrete time delays corresponding to the local maximums and minimums of the horizontal displacement amplitudes and residual horizontal displacements of the working block satisfied the canonical sequences with the multiple of √2,most of which satisfied the quantitative expression (√2)~i △/V_p.Besides,the one-dimensional impact experiments were carried out on the blocks granite model,continuum,and blocks cement mortar models,respectively.Based on the comparison and analysis of the propagation properties (amplitudes and the Fourier spectrums of acceleration time histories of blocks) of the 1D stress wave in the above models,it is indicated that the fractures in rock mass have tremendous effect on the attenuation of acceleration amplitudes and high-frequency waves.By comparison of the model test data with the in situ measurement conclusions,the existence of the μ wave was confirmed experimentally in the cement mortar blocks model with larger dimensions,and the frequencies corresponding to the local maximums of spectral density curves of three-directional acceleration time histories of sub-blocks also satisfied several canonical sequences with the multiple of √2.     

涡旋盘端面的摩擦研究

根据运动过程中的润滑状态,摩擦力一般产生于两个方面,一是黏性流体的剪应力,二是摩擦界面相互接触峰元的剪切作用.针对这两方面因素,基于对涡旋盘在运动过程中处于混合润滑状态的分析,考虑到动涡盘受倾覆力矩的作用,在运转过程中瞬间发生弹性变形,接触面上产生楔形角,建立了动静涡旋盘摩擦模型;运用平均雷诺方程和固体接触理论,推导了摩擦力和摩擦功耗的计算公式,并且应用有限差分法和数值积分法对实际的涡旋盘的摩擦力、摩擦功耗作了计算.