|Alternative Title||Theory and applications of laminated island-bridge structures of flexible electronics in structural monitoring and detection of high-speed train|
|Place of Conferral||北京|
Flexible electronics have extensive application prospects; however, most related researches focus on flexible wearable devices, while little attention has been paid to conventional industries. As a typical structure of flexible electronics, the island-bridge structure can not only integrate various functional components but also achieve stretchability, which results in wide potential applications in large-scale transportation equipments with complex surfaces such as high-speed trains. Therefore, it is worth researching on the island-bridge structure of flexible electronics in those equipments. First, this dissertation develops some mechanics researches on the stiffnesses of laminated bridges of island-bridge structures in order to guide quantitative analysis and design of the deformation of island-bridge structures. Then, laminated island-bridge structures are applied to the fabrication of two flexible electronics, which aim for surface pressure monitoring of the high-speed train locomotive and ultrasonic nondestructive detection of the high-speed train axles, respectively.
Laminated structures have been widely adopted in the stretchable interconnects of island-bridge structures, and both their tensile and bending stiffnesses, which act as key mechanical parameters, have been widely applied to the mechanical analyses for the island-bridge mesh structures. Nowadays, researchers usually get the tensile or bending stiffness with the plane-strain assumption. However, it is found that the practical condition is usually closer to the traction-free condition. Here, a traction-free model is proposed to analytically obtain the effective tensile and bending stiffnesses of laminated structures. According to this dissertation, the tensile/bending stiffnesses of the traction-free model are between the plane-strain model and the plane-stress model, and are closer to those of the plane-stress model. Besides, the traction-free model is found to be more accurate than both plane-strain and plane-stress models. Meanwhile, this work has also explored the mechanism why there are some differences among these three analytical models when calculating the tensile stiffnesses of laminated structures. The traction-free model can provide valuable guidance to quantitative deformation analyses and design of the island-bridge structures.
At present, the pressure tap technique is usually adopted for the measurement of surface pressure for high-speed train. However, it is very difficult or even impossible for this technique to measure the surface pressure field in local small area with complex surface such as the locomotive, and this technique could cause some damage to high-speed train body, and it is difficult to install or replace its pressure measurement system. This work reports a kind of large-scale and stretchable pressure sensor array with the design of laminated island-bridge structures connected by curved bridges, which aims for the measurement of surface pressure field for high-speed train locomotive. The results of the finite element modeling and tensile experiment show an excellent stretchability (50%) of this pressure sensor array. Besides, the moving high-speed train model test and numerical simulation validate the accuracy and reliability of this pressure array in measuring surface pressure fields.
Conventional ultrasonic probes such as single crystal probe and phased array probe are usually rigid, and it is difficult to apply them to the nondestructive detection of curved workpieces. In this work, a flexible ultrasonic phased array transducer with the design of laminated island-bridge structures connected by linear bridges is designed and fabricated, which aims for the nondestructive detection of high-speed train axles. All array elements made from 1-3 piezo-composite were bonded together with silicon rubber to form a flexible array; each array element owns its individual backing layer and matching layer; the flexibility and the electrical connection of 12*12 autonomous signal channels are achieved with laminated flexible printed circuit board. The experimental results of pulse echo experiment, defect echo experiment and defect imaging experiment indicated that this flexible ultrasonic phased array can achieve the nondestructive testing for curved workpieces accurately.
|尹世珍. 柔性电子多层岛桥结构在高铁结构监测和检测中的理论与应用研究[D]. 北京. 中国科学院大学,2019.|
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