Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed. Optimizing the mathematical model with respect to sever...Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed. Optimizing the mathematical model with respect to several variables it is found that in addition to adhering, tearing, ploughing, etc., asperities workpiece can move wave-like along the surface layer and under certain circumstances they may disappear. If the asperities wavily move along the surface layer the friction coefficient depends on the geometry of asperities. However, the bonding strength of asperities, has no significant influence on friction coefficient. The depth of the plastic deformation layer is related to the geometry of asperities, too. The soundness of the prerequisite of the proposed model and some analytical results were verified by experiments.展开更多
不规则超低摩擦现象是深部块系岩体典型动力学特征现象之一,集中反映了深部块系岩体非协调、非连续的动力学特性。基于俄罗斯Kurlenya M V院士的深部岩体超低摩擦实验建立了深部块系岩体一维动力模型,得出了工作块体水平位移的解析表达...不规则超低摩擦现象是深部块系岩体典型动力学特征现象之一,集中反映了深部块系岩体非协调、非连续的动力学特性。基于俄罗斯Kurlenya M V院士的深部岩体超低摩擦实验建立了深部块系岩体一维动力模型,得出了工作块体水平位移的解析表达式。研究结果表明,一维动力模型理论计算结果与实验数据吻合较好,进一步揭示了深部岩体不规则超低摩擦现象产生的力学条件为分别作用于块系和工作块体上的竖向和水平冲击的时间间隔满足倍数为2的规范序列,指出超低摩擦现象产生机理在于强动载作用下块体间法向力重分布和动摩擦系数不断变化的共同作用,同时说明超低摩擦现象出现的离散周期和低频低速变位摆型波频谱具有密切联系。展开更多
以液压缸的运动特性为研究对象,首先通过揭示其非线性弹簧刚度呈现出软硬弹簧现象的产生机理,以及时变摩擦力处于负阻尼状态时引起"自激振荡"现象的原因,深入研究了二者耦合作用下液压缸的非线性时变动力学方程;而后,基于Tay...以液压缸的运动特性为研究对象,首先通过揭示其非线性弹簧刚度呈现出软硬弹簧现象的产生机理,以及时变摩擦力处于负阻尼状态时引起"自激振荡"现象的原因,深入研究了二者耦合作用下液压缸的非线性时变动力学方程;而后,基于Taylor展开法将非线性动力学方程简化为可解的线性微分方程形式,并根据离散时域步长的原理反复迭代解决非线性弹簧刚度和时变摩擦力对液压缸运动特性的耦合作用问题;最后,采用Matlab软件编制数值仿真程序,模拟液压缸低速运动时的爬行现象。仿真结果显示,爬行现象模拟效果良好,且与以往解决非线性耦合问题的Van Der Pol-Duffing方程和Lienard方程相比,本文所提的数值仿真方法具有求解方便、适用性广,精度较高等优点。展开更多
基金This is a project of the cooperative program between the Department of Materials Engineering of Northwestern Polytechnical University of the People's Republic of China and the Institute for Metal Forming at Lehigh University of the United States of Ameri
文摘Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed. Optimizing the mathematical model with respect to several variables it is found that in addition to adhering, tearing, ploughing, etc., asperities workpiece can move wave-like along the surface layer and under certain circumstances they may disappear. If the asperities wavily move along the surface layer the friction coefficient depends on the geometry of asperities. However, the bonding strength of asperities, has no significant influence on friction coefficient. The depth of the plastic deformation layer is related to the geometry of asperities, too. The soundness of the prerequisite of the proposed model and some analytical results were verified by experiments.
文摘不规则超低摩擦现象是深部块系岩体典型动力学特征现象之一,集中反映了深部块系岩体非协调、非连续的动力学特性。基于俄罗斯Kurlenya M V院士的深部岩体超低摩擦实验建立了深部块系岩体一维动力模型,得出了工作块体水平位移的解析表达式。研究结果表明,一维动力模型理论计算结果与实验数据吻合较好,进一步揭示了深部岩体不规则超低摩擦现象产生的力学条件为分别作用于块系和工作块体上的竖向和水平冲击的时间间隔满足倍数为2的规范序列,指出超低摩擦现象产生机理在于强动载作用下块体间法向力重分布和动摩擦系数不断变化的共同作用,同时说明超低摩擦现象出现的离散周期和低频低速变位摆型波频谱具有密切联系。
文摘以液压缸的运动特性为研究对象,首先通过揭示其非线性弹簧刚度呈现出软硬弹簧现象的产生机理,以及时变摩擦力处于负阻尼状态时引起"自激振荡"现象的原因,深入研究了二者耦合作用下液压缸的非线性时变动力学方程;而后,基于Taylor展开法将非线性动力学方程简化为可解的线性微分方程形式,并根据离散时域步长的原理反复迭代解决非线性弹簧刚度和时变摩擦力对液压缸运动特性的耦合作用问题;最后,采用Matlab软件编制数值仿真程序,模拟液压缸低速运动时的爬行现象。仿真结果显示,爬行现象模拟效果良好,且与以往解决非线性耦合问题的Van Der Pol-Duffing方程和Lienard方程相比,本文所提的数值仿真方法具有求解方便、适用性广,精度较高等优点。
