基于HHT的内螺纹冷挤压成形过程振动信号的研究

提出了内螺纹冷挤压振动信号的时频分析新方法：Hilbert—Huang变换。将内螺纹冷挤压振动信号分成了开机未挤压、挤压、挤压与校正、校正阶段，对4个阶段的信号进行了EMD分解，并对分解结果做了Hilbert变换，得到Hilbert谱和边际谱。分析结果表明，在内螺纹冷挤压过程中，由于丝锥与工件间产生了高频摩擦，高频成分在挤压阶段出现，并在之后的过程中高频能量出现变化，揭示了内螺纹冷挤压过程中高频摩擦的变化规律。

The HHT -based Vibration Signal of Cold Extrusion Forming Process for the Internal Thread

It proposes the time and frequency analysis of vibration signal for the cold extrusion forming of internal thread. The vibration signal of cold extrusion forming for internal thread is divided into four periods （ non extru- ding period, extruding period, extruding with correcting period and correcting period）. It applies Hilbert - trans- form to the results of the four periods obtained by EMD, generates the Hilbert spectrum and marginal spectrum. The analytical results show that high frequency （approximate 600Hz） appears during the extruding period in the whole process, and high frequency of friction between extrusion tap and workpiece leads to the energy changes of high frequency.