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Liu L.,Zhejiang University | Liu L.,Harbin University of Science and Technology | Wang Q.,Zhejiang University | Lan H.,Harbin University of Science and Technology | And 2 more authors.
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2010

Aiming at recognition of the arc sound signal in different welding status, the mechanism of arc sound generation and propagation were investigated to MIG butt welding with spray transfer. It is proposed that arc sound is an associated thing of gas discharge, is the result of transmitting by the wave when the plasma collectively vibrates, is also the outcome of their combined action, including the sound source and the sound track. Among them, the spectrum characteristic depends mainly on the frequency respond of sound track. Based on the above analysis, the linear generation model of arc sound was set up. The linear prediction coefficients (LPC){ai}, reflection coefficients and logarithm area ratio coefficients were extracted by Levinson-Durbin algorithm. In addition, the combined characteristic vector of arc sound signal was constructed. Source


Hongtao S.,Zhejiang University | Hongtao S.,Harbin University of Science and Technology | Liu L.,Zhejiang University | Liu L.,Harbin University of Science and Technology | And 3 more authors.
Applied Mechanics and Materials | Year: 2012

There are errors during the manufacturing and assembling of horizontal driving machine (HDM). So the exceptional knocking noise is generated during some products running. The failure rate of product quality is rising as well. The forward and reverse driving noise of HDM was tested and analyzed. Pictures was collected by universal tool microscope. The results show that hot runner is not smooth enough to reduce transferring pressure and increase the shrinkage of worm pouring gate. The situation leads to slight conical degree of product and pitch deviation at worm pouring gate. As the pitch makes worm inset slightly worm gear when clockwise rotating, the noise and vibration was produced consequently in this direction. The proposals were given, such as strengthening the maintenance of hot runners, controlling and inspecting product conical degree, and optimizing HDM mould and increasing its accuracy, and so on. © (2012) Trans Tech Publications, Switzerland. Source


Liu L.,Zhejiang University | Liu L.,Ningbo Shuanglin Group Co. | Yang K.,Zhejiang University | Li F.,Ningbo Shuanglin Group Co. | And 3 more authors.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2010

As there are the collision and burr on tooth surface during the manufacturing and assembling of horizontal driving machine(HDM) in automobile seats, the exceptional knocking noise is generated during automobile seat running. The returned HDM causes huge economic losses of manufacturer. The knocking noise of HDM can be effectively identified beyond 12 kHz by analyzing sound frequency band of ear feeling, knocking noise characteristics of HDM, and 1/3 octave filtering and Gabor time-frequency analysis of HDM sound signals. The methods can avoid interference of high-energy signals from 3 kHz to 8 kHz on knocking noise of HDM. The conclusion provides a automatic identification way of knocking noise of horizontal driving machine in automobile seats. Source

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