铁电材料中声波诱发电畴变的低频吸声机理研究

PZT shunted damping is widely used in structural vibration suppression and vibration energy harvesting. It is typically suitable for the cases where the vibration frequency is not too low. For low frequency sound absorption, the performance of PZT shunted damping is far from satisfactory. In the current proposal, the research plan is to utilize polarization reorientation in ferroelectric materials, which is induced via the impinge sound wave, to enhance low frequency sound absorption..In the current research, appropriate composite structure is designed to induce polarization switching in ferroelectric materials via the imping wave. It is expected that large amount of mechanical energy will be converted into electric form when polarization reorientation is induced by mechanical loadings. Meanwhile, a part of the vibration energy will be converted into thermal form directly due to heat of transformation. Phenomenological theory for phase transition will be used to study the polarization switching dynamics and the energy conversion mechanism during the processes. The mechanism of low frequency sound absorption will be investigated and the coupled dynamics of the nonlinear electro-mechanical constitutive relation with the shunted damping circuit will be modeled and analyzed. Experimental investigations will be performed on composite oscillators made from ferroelectric ceramics together an elastic beam. Nonlinear vibration of the composite structure will be analyzed and optimized for maximum energy conversion. Composite coatings will be made from ferroelectric materials together with polymers, and its sound absorption performance will be tested by using acoustic tube with two microphones..The outcome of the current research is a thorough understanding of the mechanism of passive low frequency sound absorption by using stress induced polarization switching. The aim of the current research is to remarkably enhance low frequency underwater sound absorption. The theoretic results about the polarization switching dynamics and accompanying energy conversion gained in the current research is also highly valuable for other smart materials and structures.

压电分流阻尼技术在中高频噪声控制和振动抑制中得到了广泛应用，但难以扩展到低频振动情况。本项目拟研究利用铁电材料中的声波诱发电畴变所特有的强机械阻尼特性，将振动能转换成电能和热能，实现低频吸声。项目拟研究低频入射声波在铁电材料中诱发的90度电畴翻转，以及伴随电畴变过程的振动能向电能和热能的转换；采用相变理论对电畴变的动力学进行理论分析；研究电畴变过程中偏置应力、偏置压力对非线性力电耦合关系的影响规律；研究非线性力电耦合效应与分流阻尼电路耦合的系统动力学及其优化；阐明基于应力诱发电畴变的低频吸声机理，揭示低频振动情况下振动能向电能和热能转换的影响因素及规律；研制基于铁电材料的新型低频吸声覆盖层，并开展实验研究。这种新型的低频吸声机理研究，将为大幅减少低频探测声波的反射量，提高水下航行器的声隐身性能奠定坚实基础。这种非线性能量损耗机理在低频振动抑制和微小振动能量捕获方面也有重要的参考价值。

低频噪声对人类健康是有害的并且在低频噪声的吸收在军事上也有重要的意义。因为因此找到一种有效的方法来吸收低频噪音，或至少在一定程度上减弱低频噪音，是很有必要的。本研究基于铁电材料电畴翻转特性，利用朗道理论研究声波诱发铁电材料中电畴变翻转最终实现低频吸声的目的。在这个过程中铁电材料表现出强机械阻尼特性，并通过将振动能转换成电能和热能，实现低频吸声。声波本质上是一种振动，利用振动放大装置将声波产生的振动进行放大，之后将放大的振动施加到铁电材料上，进而诱发材料的极化翻转，这样在材料的表面会产生电压。通过设计的外接电路，将产生的电能转化为热能耗散掉，以此来达到能量耗散的目标。铁电材料在周期性外加振动下产生的极化反应具有滞回特性，该滞回特性具有很强的阻尼性，并且一部分声波的机械能可以以相变热的形式直接转化为热能，这样可以极大地提升能量耗散地效率。另外对于单个循环来说，声波的频率越低，铁电材料用来完成极化翻转的时间就越充足，因此利用铁电材料来进行低频声波吸收具有天然的优势。铁磁材料内部是由许多磁畴组成的，在外加磁场和应力的作用下也可进行极化翻转来实现力磁之间的相互转化，以此来达到能量耗散的目的，本质上与铁电材料是相同的，因此铁磁材料也属于本研究的范围之内。本研究利用了相场法和朗道相变理论对铁电以及铁磁单晶和多晶材料的性质进行了深入的研究和模拟分析，为后面实验的开展打下了坚实的基础。本文利用所建立的铁电材料的本构方程，对铁电材料进行了能量耗散方面的研究，探究了其对偏置应力、频率以及外接电阻的依赖性，研究表明，适当增大电阻可以有效降低材料的对低频声波的吸收效果，验证了声波吸收的可行性。