不同围压实验变形物质中的微观滑移方式标志研究

通过不同围压条件下岩石破裂粘滑或稳滑实验样品的微观对比观测研究，分析了压力对滑移方式标志的可能影响，提出在不同围压条件下，变形物质中赋存的微观粘滑或稳滑的识别标志，为类似围压条件下形成的天然样品微观滑移方式标志的识别提供了实验判据。     

具有局部非线性动力系统周期解及稳定性方法

对于具有局部非线性的多自由度动力系统，提出一种分析周期解的稳定性及其分岔的方法该方法基于模态综合技术，将线性自由度转换到模态空间中，并对其进行缩减，而非线性自由度仍保留在物理空间中在分析缩减后系统的动力特性时，基于Ｎｅｗｍａｒｋ法的预估－校正－局部迭代的求解方法，与Ｐｏｉｎｃａｒé映射法相结合，推导出一种确定周期解，并使用Ｆｌｏｑｕｅｔ乘子判定其稳定性及分岔的方法     

Multiple Non-Smooth Events in Multi-Degree-of-Freedom Vibro-Impact Systems

The behaviour of a multi-degree-of-freedom vibro-impact system is studied using a 2 degree-of-freedom impact oscillator as a motivating example. A multi-modal model is used to simulate the behaviour of the system, and examine the complex dynamics which occurs when both degrees of freedom are subjected to a motion limiting constraint. In particular, the chattering and sticking behaviour which occurs for low forcing frequencies is discussed. In this region, a variety of non-smooth events can occur, including newly studied phenomena such as sliding bifurcations. In this paper, the multiple non-smooth events which can occur in the 2 degree-of-freedom system are categorised, and demonstrated using numerical simulations.     

水润滑高速动静压轴承试验研究

研究了动静压轴承在水介质润滑和高速、高压极端工况条件下,最小液膜厚度和流量等性能参数的变化情况,并将其与理论预测结果进行比较.结果表明,水润滑动静压轴承在高速时能够稳定运行,且形成完整的润滑液膜,没有出现明显的汽化及汽蚀现象,试验后轴承表面涂层基本完好.试验结果显示出轴承的承载能力和流量主要取决于供水压力,这与理论预测结果基本一致.     

Dynamic shearing resistance of molten metal films under high pressures and extremely high shearing rates

In the present study plate-impact pressureshear experiments have been conducted to study the dynamic shearing resistance of molten metal films at shearing rates of approximately 10⁷ s⁻¹. These molten films are generated by pressure-shear impact of relatively low melt-point metals such as 7075-T6 Al alloy with high hardness and high flow-strength tool-steel plates. By employing high impact speeds and relatively smooth impacting surfaces, normal interfacial pressures ranging from 1–3 GPa and slip speeds of over 100 m/s are generated during the pressure-shear loading. The resulting friction stress (∼100 to 400 MPa) combined with the high slip speeds generate conditions conductive to interfacial temperatures approaching the fully melt temperature regime of the lower melt-point metal (7075-T6 aluminum alloy) comprising the tribo-pair. During pressure-shear loading, laser interferometry is employed to measure normal and transverse motion at the rear surface of the target plate. The normal component of the particle velocity provides the interfacial normal traction while the transverse component provides the shearing resistance of the interface as it passes through melt. In order to extract the critical interfacial parameters, such as the interfacial slip-speed and interfacial temperatures, a Lagrangian finiteelement code is developed. The computational procedure accounts for dynamic effects, heat conduction, contact with friction, and full thermo-mechanical coupling. At temperatures below melt the flyer and target materials are described as an isotropic thermally softening elastic-viscoplastic solid. For material elements with temperatures in excess of the melt point, a purely Newtonian fluid constitutive model is employed. The results of this hybrid experimental-computational study provide insights into the dynamic shearing resistance of molten metal films at high pressures and extremely high shearing rates.     

滑动干摩擦条件下铸铁的摩擦学特性研究

系统地研究了铸铁材料在干滑动摩擦条件下的摩擦学特性。考察了铸铁石墨形态、合金元素及基体组织对其与钢配副时的滑动摩擦学特性的影响。研究结果表明：蠕墨铸铁具有良好的摩擦磨损特性；在铸铁中加入合金元素P和B可显著改善摩擦副的性能；同时，铸铁的基体组织对于摩擦磨损特性有十分显著的影响。     

基于滑模趋近律的防空导弹垂直发射姿态控制研究

利用四元数在弹体坐标系下对垂直发射的防空导弹建立了运动方程,并在纵向通道利用小扰动线性化状态空间模型,设计了基于滑模趋近律的姿态控制律,最后建立了Simulink六自由度弹道模型并进行了数字仿真,结果表明：基于四元数的运动方程形式运行有效,基于滑模趋近律的姿态控制律可实现对防空导弹垂直发射的有效控制。     

Rolling/sliding of a particle on a flat wall in a linear shear flow at finite Re

Recently Lee and Balachandar proposed analytically-based expressions for drag and lift coefficients for a spherical particle moving on a flat wall in a linear shear flow at finite Reynolds number. In order to evaluate the accuracy of these expressions, we have conducted direct numerical simulations of a rolling particle for shear Reynolds number up to 100. We assume that the particle rolls on a horizontal flat wall with a small gap separating the particle from the wall (L = 0.505) and thus avoiding the logarithmic singularity. The influence of the shear Reynolds number and the translational velocity of the particle on the hydrodynamic forces of the particle was investigated under both transient and the final drag-free and torque-free steady state. It is observed that the quasi-steady drag and lift expressions of Lee and Balachandar provide good approximation for the terminal state of the particle motion ranging from perfect sliding to perfect rolling. With regards to transient particle motion in a wall-bounded shear flow it is observed that the above validated quasi-steady drag and lift forces must be supplemented with appropriate wall-corrected added-mass and history forces in order to accurately predict the time-dependent approach to the terminal steady state. Quantitative comparison with the actual particle motion computed in the numerical simulations shows that the theoretical models quite effective in predicting rolling/sliding motion of a particle in a wall-bounded shear flow at moderate Re.     

平面滑动型岩质边坡稳定性极限分析上限法

在极限分析理论框架体系的基础上,提出了平面滑动型岩质边坡极限分析上限法。该方法按照外力所做的功率等于内力所消耗的功率,即滑体处于极限状态时两功率相等的条件——虚功率方程,综合考虑作用在岩质边坡上的后缘裂缝静水压力、沿滑面扬压力、重力、水平地震作用力、锚固力等外力,按照强度折减法,推导得出了岩质边坡稳定性评价的极限分析上限解。锦屏一级水电站右岸泄洪洞引渠内侧工程边坡属于典型的多级台阶状岩质高边坡,该边坡岩体结构为层状结构,变形破坏模式为平面滑动。对引渠内侧岩质边坡稳定性分析结果表明,极限分析上限法对平面滑动型岩质边坡有较好的适用性。     

高速列车轴承可靠性评估关键力学参量研究进展

轴承是高速列车牵引传动和轮轴系统的关键零部件. 受列车运行过程中电机转矩、齿轮啮合以及轮轨随机激励的影响,轴承可能发生疲劳破坏, 严重影响高速列车的行车安全.我国特有的复杂运用条件对轴承部件的疲劳性能提出了更高的要求,而轴承疲劳可靠性的基础理论和关键技术是我国轴承正向设计研发中的薄弱环节.可靠性评估方面的相关研究在解决轴承可靠性研究的瓶颈问题中起到了承上启下的关键作用.高速列车轴承可靠性评估手段与技术旨在获得使用环境中轴承可靠性评估的关键力学参量,并以此推动复杂激励下轴承疲劳可靠性理论研究. 因此,需要哪些关键力学参量并且在复杂的实际使用环境下如何去获取这些力学参量是进行高速列车轴承可靠性评估的关键所在.本文首先概述了高速列车轴承所处的复杂使用环境及运用中的主要失效模式,并据此分析了高速列车轴承可靠性评估所需的关键力学参量,强调了轴承内部滚滑行为和载荷分布在可靠性评估和轴承状态监测中的重要作用,之后从计算模型和测试技术等方面系统阐述了针对这两个关键力学参量的研究进展.最后提出了在高速列车轴承可靠性评估关键力学参量特征及测试技术研究中值得关注的若干问题.