Ultrasonic bonding has an increasing application in the micro assembly of polymeric micro-electro mechanical systems (MEMS) with high requirements for fusion precision. In the ultrasonic bonding process, the propagation of ultrasonic vibration in polymer components is related to the interfacial fusion, which can be used as a monitoring parameter to control ultrasonic energy. To study the vibration propagation in viscoelastic polymer components, finite element analysis on the bonding of poly methyl methacrylate (PMMA) micro connector to substrate for microfluidic system is carried out. Curves of propagated vibration amplitude corresponding to interfacial temperatures are obtained. The ultrasonic vibration propagated in PMMA components are measured through experiments. The theoretical and experimental results are contrasted to analyze the change mechanism of vibration propagation related to temperature. Based on the ultrasonic bonding process controlled by the feedback of vibration propagation, interfacial fusions at different vibration propagation states are obtained through experiments. Interfacial fusion behavior is contrasted to the propagated vibration amplitude in theoretical and experimental studies. The relation between vibration propagation and fusion degree is established with the proper parameter range for the obtained high quality bonding.
Fusion precision is an important factor to be considered for ultrasonic bonding in thermoplastic MEMS. Vibration transmission in ultrasonic bonding process through polymer workpiece was related to the interfacial fusion, which could be used for in situ monitoring. In this article, experimental platform was established to study the vibration transmission. Experiments were carried out to measure the vibration transmitted from horn onto the high-frequency dynamic force sensor installed in the anvil. According to the peak-to-peak value of dynamic force, the whole bonding process could be divided into rising and falling phases. Interfacial fusion corresponding to ultrasonic transmission was also studied. From experimental results, when the peak-to-peak value change rate rose to 130%, some area on the surface starts to melt. When it fell down back to 60%, glass transition occurred with the melt spread gradually over the whole interface. When it fell down to 30%, defects of overflow and bubble began to generate as polymer got into viscous flow state. When the change rate reached 10%, the bubbles burst into smaller ones like floccules as the fluidity of polymer was enhanced further under continuous ultrasonic load. The experimental results gave a deep understanding in the formation of interfacial fusion and the generation of defects.
This paper takes the Section 201 of shield construction engineering in Dalian Metro Line 2 as an example to analyze the deformation law of surrounding soil and the tunnel lining structure stress during shield tunnel construction. The shield tunnel construction is simulated dynamically by ADINA and the shield tunnel structure model of the concrete lining is established. This model is a three-dimension nonlinear finite element calculation model concerned with the grouting soil and original state soil. Taking the soil lithology in the upper layer and interact influences, we analyzed the dynamic process of shield construction, soil grouting and lining supporting and the stress distribution in difference reinforced concrete supporting segments and the ground settlement characteristics. Through numerical analysis method to study the deformation law of soil surrounding tunnel and the stress in tunnel lining, we get the results to compare with the results of Peck formula under the same condition. After generating the conclusions, we can provide several suggestions for shield tunneling construction, lining segment design and control of the ground surface settlement during the construction.
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