考虑壁面滑移的磁流变胶泥缓冲器设计理论与落锤冲击试验

Design methodology for magnetorheological energy absorbers considering wall slip and falling weight impact tests

为提高汽车碰撞磁流变缓冲器力学模型的准确性,实现冲击作用下磁流变缓冲器动态特性的高精度预测,基于Herschel-Bulkley模型,同时考虑表观滑移和壁面滑移,建立了缓冲器理论力学模型。通过分析表观滑移和壁面滑移对缓冲器阻尼通道内部压力梯度的影响,结果表明,载液黏度较低时,受表观滑移影响,阻尼通道内部压力梯度有所降低,且在低速下影响更加显著;随着载液黏度的增加,在表观滑移作用下压力梯度有所增加,但对总体影响不大;壁面滑移使通道内部压力梯度明显降低,且随着滑移系数的增加,压力梯度变化更为显著;不同电流、冲击速度下的缓冲器落锤冲击试验表明,理论模型能够较好地预测、表征磁流变缓冲器的力学特性;磁流变胶泥在通道内流动主要受壁面滑移的影响,未出现明显的表观滑移。

To improve the accuracy of mechanical models and achieve high precision prediction of dynamic characteristics of magnetorheological energy absorbers under impact,the Herschel-Bulkley constitutive model was modified by considering the apparent slip and wall slip conditions.By analyzing the influence of apparent slip and wall slip conditions on the pressure gradient in the damper channel,the results show that the pressure gradient decreases with the viscosity of carrier fluid decreasing under the influence of apparent slip condition,and the influence is more significant at low velocity.The pressure gradient increases with the viscosity of carrier fluid under the influence of apparent slip condition,while the effects on the overall structure are not important.The pressure gradient of the damper channel is obviously influenced by the wall slip condition,and the pressure gradient changes more significantly with the wall slip coefficient.Comparisons between measured and computed results under different currents and impact velocity reveal that the new model can well predict and characterize the mechanical properties of the magnetorheological energy absorber.The flow of magnetorheological fluid in the damper channel is mainly affected by the wall slip,and is slightly influenced by the apparent slip condition.