Insights into the regulation mechanism of ring-shaped magnetoelectric energy harvesters via mechanical and magnetic conditions*

Abstract

This paper presents a theoretical model for predicting and tuning magnetoelectric (ME) effect of ring-shaped composites, in which stress boundary conditions are empoyed and the multi-field coupling property of giant magnetostrictive materials are taken into account. A linear analytical solutions for the closed-and open-circuit ME voltages are derived simultaneously using mechanical differential equations, interface and boundary conditions, and electrical equations. For nonlinear ME coupling effect, the nonlinear multi-field coupling constitutive equation is reduced to an equivalent form by expanding the strains as a Taylor series in the vicinity of bias magnetic field. Sequentially, the linear model is generalized to a nonlinear one involving the field-dependent material parameters. The results show that setting a stress-free condition is beneficial for reducing resonance frequency while applying clamped conditions on the inner and outer boundaries may improve the maximum output power density. In addition, performing stress conditions on one of the boundaries may enhance ME coupling significantly, without changing the corresponding resonance frequency and optimal resistance. When external stimuli like bias magnetic field and pre-stress are applied to the ring-shaped composites, a novel dual peak phenomenon in the ME voltage curve around resonance frequencies is revealed theoretically, indicating that strong ME coupling may be achieved within a wider bias field region. Eventually, the mutual coordination of the bias field and pre-stress may enhance ME coupling as well as tuning the resonance frequency, and thus is pivotal for tunable control of ME energy harvesters. The proposed model can be applied to design high-performance energy harvesters by manipulating the mechanical conditions and external stimuli.

Modeling and performance analysis of resonant self-biased magnetoelectric transducers

“…磁电多铁材料通过正、逆磁电效应，实现高效的磁场、电场相互转换，因而 被广泛应用于电流传感 [1,2] 、能量收集 [3] 和低频天线 [4−6] 等领域。磁电复合材料较 单相材料具有更强的磁电效应，相关学者通过有限元 [7−9] 、等效电路 [10−12] 和弹性 力学 [13,14] 等方法研究其性能，并探讨外部激励 [15−17] 对磁电耦合的影响。然而，常 规磁电复合材料依赖永磁体或电磁铁提供偏置的磁场， 由此带来的噪声、 体积大、 成本高等问题严重限制了小型化、高性能磁电器件的发展。 为了解决该问题，研究人员持续探寻新型磁电复合材料，以实现无外加偏置 磁场的自偏置磁电效应，并尝试采用反铁磁-铁磁转换耦合效应 [18,19] 和磁性材料 的固有剩磁 [20,21] 等策略。然而，这些方法所实现的磁电耦合效应较弱，操作过程 也相对复杂，难以实际应用。Wen 等 [22,23] 将高磁导率的铁基纳米晶合金 (FeCuNbSiB)与磁电复合材料结合，通过磁化梯度分布替代偏置磁场，率先实 现了自偏置磁电效应，并提高了磁电系数和磁场灵敏度。在理论建模方面，Cheng 等 [24] 和 Lu 等 [25] 建立了包含涡流效应的非线性磁电耦合模型；Shi 等 [26] 研究了外 部激励和高磁导率层对磁电耦合性能的影响；Zhang 等 [27] 利用 COMSOL 软件揭 示了温度等外部条件对磁电系数的影响。在实验方面，Ma 等 [28] 优化了自偏置磁 电复合材料的制备和连接方法，拓宽了谐振带宽；Huang 等 [29] 通过在 PZT 层自由 端粘接 FeCuNbSiB/Ni 层，进一步增强了磁电耦合强度；Yang 等 [30] 则研究了非谐 振条件下的自偏置逆磁电效应。 以往对磁电复合材料的研究 [22−30] 多集中在结构的 电压响应，忽视了内阻抗对其输出性能的影响。随着磁电复合结构在低频无线功 率传输技术 [31−34] [26] 下的磁电换能器，其压…”