Thermo-Electric-Mechanical Coupling Bending Property and Strength Analyses of Thermoelectric Devices With the Negative Poisson's Ratio Architecture
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摘要: 随着智能可穿戴设备的快速发展,对供电元件的续航时间、便捷性以及轻量化等提出了更高要求. 热电器件可以直接将人体新陈代谢释放的热能转换为电能,为可穿戴设备持续供电. 利用整体-局部、细观-宏观相结合的分析方法,该文研究了负Poisson比热电器件的热-电-力耦合弯曲行为及其强度失效问题. 首先,通过建立负Poisson比热电器件的均质化分析模型,获取了器件的宏观弯曲特征,并给出了应力最大的截面. 然后,建立热电蜂窝的受力分析模型,利用热力学强度理论导出了胞壁的细观强度失效临界荷载. 研究发现:热电蜂窝的应力水平随着内凹角增大呈现先减小后增加的趋势;对于负Poisson比热电蜂窝,强度失效首先发生在中间部位;对于传统的六边形热电蜂窝,端部比中间部位先发生强度破坏;热电器件发生断裂破坏时,中间和端部的临界裂纹长度近似相等,可以拟合为内凹角的指数函数.
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关键词:
- 热电器件 /
- 负Poisson比结构 /
- 强度失效 /
- 多场耦合
Abstract: The rapid development of smart wearable devices makes a higher requirement for the power supply components, including endurance, convenience and lightweight and so on. The thermoelectric devices can directly convert the thermal energy released by human metabolism into electricity, which can be further used to continuously power the wearable devices. With the global-local and micro-macro combined analysis method, the thermo-electro-mechanical coupling bending behavior and strength failure of a negative Poisson's ratio thermoelectric device (NPR-TEG) were analyzed. Firstly, the macroscopic bending characteristics and the section with the largest stress were given through the establishment a homogeneous analysis model for the NPR-TEG. Then, the force analysis model for the thermoelectric honeycomb was built. The critical load for the strength failure of a mesoscopic cell wall was also derived with the thermodynamic strength theory. The results show that, the stress level of the thermoelectric honeycomb decreases first and then increases with the re-entrant angle. For the NPR-TEG, the strength failure occurred first in the middle part of the device. For the thermoelectric device with the traditional hexagonal honeycomb, the strength failure occurs at the end of the device rather than the middle part. With the fracture failure occurring in the thermoelectric device, the critical crack length of the middle fracture approximately equals that of the end fracture. The critical crack length could be fitted as an exponential function of the re-entrant angle. -
表 1 可穿戴热电器件材料属性和几何尺寸
Table 1. Material properties and geometric dimensions of the wearable thermoelectric device
parameter value Bi2Te3 K20=1.1 W/(m·K)
E20=63.3 GPaρ20=9.4×10-6 Ω·m
υ20=0.23λ=194 μV/K
α=8.98×10-6 KPDMS E1=E3=10 MPa υ1=υ3=0.495 dimension L=43 mm B=39 mm H1=H3=0.5 mm H2=2 mm h/l=2 t=0.5 mm 表 2 轴向应力最大值随弹簧刚度系数变化规律
Table 2. Material properties and geometric dimensions of the wearable thermoelectric device
parameter value k/(N/m2) 1×106 1×109 1×1012 1×1015 |σ|max/MPa 61.6 61.9 62.1 62.1 -
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