超声波焊接中振动传递特征与聚合物物态分析

Vibration transmission characteristics and polymer physical state analysis in ultrasonic bonding process

在聚甲基丙烯酸甲脂（PMMA）的超声波焊接中测量了振动传递与焊接界面温度,利用小波包分析对振动传递波形进行分解,计算了各节点能量占比,对能量主要分布的频段进行小波包单节点重构,结合温度变化实现振动传递特征的提取.结果表明：在109.375~125 k Hz频段,其重构波形频率为120 k Hz,当温度接近材料玻璃化温度时,振幅大幅度衰减;在温度达到峰值后,振幅出现微弱反弹,随后继续衰减,反映了材料储能模量减小的同时,损耗模量先增加后减小.经小波包分解重构的特征波形可以更为精细地划分界面完全熔合和过度熔合之间的临界点,可作为控制参数提高界面熔合的控制精确性.

The propagated vibration and interfacial temperature were measured in ultrasonic bonding process for polymethyl methacrylate（PMMA）.The vibration waveform was analyzed by wavelet packet decomposition with the characteristic frequency obtained.Energy ratio was calculated with main vibration components confirmed.Then the waveform in each frequency band with high energy was reconstructed.Results indicate that the frequency of reconstructed waveform in the band of 10.9375~125 k Hz is 120 k Hz.The amplitude of the waveform has a great attenuation when the interface temperature is close to the glass transition temperature.When the interface temperature reaches the peak,the vibration amplitude recovers slightly,and then decreases eventually,which shows that the loss modulus increases first and then decreases in the attenuation process of the storage modulus.The interracial fusion in full and overflow conditions can be distinguished more finely by the reconstructed waveform after wavelet packet decomposition,which can be a control parameter to improve control accuracy of interfacial fusion.