考虑法向载荷变化的Iwan模型及其特性分析

为了完整、准确地复现摩擦接触界面间的力学行为和描述其能量耗散特性,提出了一种考虑法向载荷变化的Iwan模型.在连接界面的法向上,该模型采用一个非线性弹簧来描述界面法向载荷变化和间歇性分离的行为,在其切向上则采用原始Iwan模型来描述界面间的微滑和宏滑行为;推导了切法向耦合作用下模型的恢复力和位移关系的表达式,给出了模型运动状态转换点的判据;并以简化的摩擦阻尼器模型为对象,求解了振动系统在简谐激励作用下的动力学响应,讨论了不同激励参数对系统动力学特性的影响.分析表明,当法向载荷为常值时,该模型退化为Iwan模型,从而验证了模型的准确性;该模型考虑了切向微滑行为和法向载荷变化的动态耦合,相比于不考虑法向载荷变化的模型能够更加完善、准确地模拟接触界面间的力学行为及其对系统振动响应预测的影响;连接界面的法向分离不仅会减弱系统的阻尼性能,使得系统动响应很高,而且会增强系统响应的非线性程度,在实际工程应用中应尽量避免.

Iwan model considering variable normal load and its characteristic analysis

To more comprehensively and precisely reproduce mechanical behaviors of frictional and describe properties of energy dissipation, a kind of Iwan model considering variable normal load is developed. In the normal direction, a nonlinear spring is used to describe normal load variation and intermittent separation. In the tangential direction, the original Iwan model is used to describe micro-slip and macro-slip behavior. The relationship between tangential restoring force and relative displacement is derived and the transition criteria among motion states of the model is given. A simplified friction oscillator under harmonic excitation is analyzed to study the effect of different parameters of excitation on the system responses. The proposed model degrades into the original Iwan model when the normal load keeps constant, which validates the model well. This model considering coupling of micro-slip tangential force and variable normal force more comprehensively, exactly reproduces contact interface and effect on the system response. The separation of interface not only reduces damping capability of friction system and makes the responses high, but also strengthens nonlinearity of the system, so it should be avoided in the practical engineering.