约束阻尼型镗杆的优化及减振性能

孔加工过程中镗杆的切削颤振影响着表面加工质量和加工精度,约束阻尼型镗杆可有效抑制这种切削振动,但其作用机理未被完全研究清楚,导致其抑制振动的效果一般。对约束阻尼型镗杆的结构优化、材料优选及减振性能进行了理论和实验研究。首先,根据Kelvin-Voigt粘弹性力学模型理论建立了镗杆的动力学模型,研究证实增大镗杆的静刚度和结构损耗因子能提高其减振性能从而提高孔加工质量;其次,基于建立的约束阻尼型镗杆静刚度和结构损耗因子理论公式,对其进行结构优化、材料优选。结果显示:存在一个最佳尺寸范围可减小镗杆在主要工作频域段上的振动,同时所选用的阻尼层应具有较小的弹性模量和较大的材料损耗因子,约束层材料应具有较大的弹性模量;最后,设计制造4种不同材料的约束阻尼型镗杆,通过模态实验获得静刚度、结构损耗因子,并与理论计算结果进行对比分析,同时研究切削过程中约束阻尼型镗杆的材料及切削参数对减振性能的影响。结果显示:约束阻尼型镗杆能有效减小径向振动以提高加工质量,不同材料的约束阻尼型镗杆在切削过程中径向振动差别较大,优化后的钢-PMMA-硬质合金镗杆在不同切深及转速下的径向振动加速度较小且更加稳定。

Optimization and damping performance of constrained damping boring bar

The constrained damping boring bar can effectively reduce the cutting chatter affecting the surface quality and accuracy in hole machining, but the effect is not significant because the mechanism has not been fully found out. The theoretical and experimental research of the structure optimization, optimal material selection and vibration damping characteristic of the constrained damping boring bar is finished in this paper. Firstly, the dynamics model of the constrained damping boring bar is established through Kelvin-Voigt's viscoelastic mechanics model theory, and it is proved that the increase of static stiffness and loss factor of the boring bar can enhance the vibration damping performance to improve the quality of machining. Secondly, structure optimization and optimal material selection are completed based on the static stiffness and loss factor theory formula, and the result shows that there is an optimal size range that can reduce the vibration on the main working frequency domain, then it is shown that the elastic modulus of damping layer should be reduced while the elastic modulus of constraining layer and the material loss factor of damping layer should be increased. Finally, four constrained damping boring bars with different materials are designed and manufactured, and the modal experimental results of the static stiffness and loss factor have little difference with the theoretical calculation results. Further study of the influence of material and cutting parameters on the vibration damping performance in machining shows that constrained damping boring bars can effectively reduce the radial vibration to improve the surface quality. The radial vibration of constrained damping boring bars with different materials has great differences in cutting process, and the radial vibration acceleration of the optimized steel-PMMA-carbide boring bar is smaller and more stable at different cutting depths and spindle speeds.