建立了内嵌单个声学黑洞板结构与阻尼的有限元模型,通过功率流和波数域法分析了板内弯曲波的全频带能量分布特性,并进一步研究了板内嵌有声学黑洞阵列结构的能量汇聚效应,探究了不同激励频率下声学黑洞阵列与阻尼的耦合作用机理。结果表...建立了内嵌单个声学黑洞板结构与阻尼的有限元模型,通过功率流和波数域法分析了板内弯曲波的全频带能量分布特性,并进一步研究了板内嵌有声学黑洞阵列结构的能量汇聚效应,探究了不同激励频率下声学黑洞阵列与阻尼的耦合作用机理。结果表明,相比于普通薄板,带有阻尼的声学黑洞阵列结构能够显著改善结构振动及向外的辐射噪声,声辐射降低量最大可以达到10 d B,在结构的减振降噪与轻量化方面具有应用潜力。展开更多
The ultrasonic attenuation coefficient is one of the most important acoustic parameters to character the performance of a thin layer media, but it can not be measured due to mutual superposition of multiple reflected ...The ultrasonic attenuation coefficient is one of the most important acoustic parameters to character the performance of a thin layer media, but it can not be measured due to mutual superposition of multiple reflected waves at the same interface in ultrasonic testing. Ultrasonic pulse echo and lamb wave to evaluate the thin layer media can not obtain attenuation coefficient at present. In this paper, analytical method was used to study the acoustics characteristic of thin layer media with the ultrasonic echo testing. Meanwhile, the process of ultrasonic attenuation measurement was presented. Simulation and experimental investigation is focused on a thin layer of rubber. Attenuation coefficient was introduced and evaluation mathematics model was established by the two echoes cross-correlation with and without the thin layer media based on the time delay spectrum. It involved the parameters related to the acoustic properties of the thin layer media. Through calculating the sound velocity and acoustic impedance with the evaluation model, it can deduce the relation between the attenuation coefficient and the frequency. Through analyzing the simulation results, it indicated that the attenuation coefficients were invariable with the varying of the frequency. However, the attenuation coefficients increased with the frequency increasing by ultrasonic testing the thin layer of rubber. The reason was that the attenuation factor was not taken into account during the simulation. This method overcomes shortcomings that the traditional ultrasonic testing can not evaluate the thin layer media whose thickness is less than motivation wavelength. It is a new solution to study the attenuation characteristic and on-line nondestructive evaluation in the thin layer media.展开更多
文摘建立了内嵌单个声学黑洞板结构与阻尼的有限元模型,通过功率流和波数域法分析了板内弯曲波的全频带能量分布特性,并进一步研究了板内嵌有声学黑洞阵列结构的能量汇聚效应,探究了不同激励频率下声学黑洞阵列与阻尼的耦合作用机理。结果表明,相比于普通薄板,带有阻尼的声学黑洞阵列结构能够显著改善结构振动及向外的辐射噪声,声辐射降低量最大可以达到10 d B,在结构的减振降噪与轻量化方面具有应用潜力。
基金supported by National Natural Science Foundation of China (Grant No. 50802009)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070151024)
文摘The ultrasonic attenuation coefficient is one of the most important acoustic parameters to character the performance of a thin layer media, but it can not be measured due to mutual superposition of multiple reflected waves at the same interface in ultrasonic testing. Ultrasonic pulse echo and lamb wave to evaluate the thin layer media can not obtain attenuation coefficient at present. In this paper, analytical method was used to study the acoustics characteristic of thin layer media with the ultrasonic echo testing. Meanwhile, the process of ultrasonic attenuation measurement was presented. Simulation and experimental investigation is focused on a thin layer of rubber. Attenuation coefficient was introduced and evaluation mathematics model was established by the two echoes cross-correlation with and without the thin layer media based on the time delay spectrum. It involved the parameters related to the acoustic properties of the thin layer media. Through calculating the sound velocity and acoustic impedance with the evaluation model, it can deduce the relation between the attenuation coefficient and the frequency. Through analyzing the simulation results, it indicated that the attenuation coefficients were invariable with the varying of the frequency. However, the attenuation coefficients increased with the frequency increasing by ultrasonic testing the thin layer of rubber. The reason was that the attenuation factor was not taken into account during the simulation. This method overcomes shortcomings that the traditional ultrasonic testing can not evaluate the thin layer media whose thickness is less than motivation wavelength. It is a new solution to study the attenuation characteristic and on-line nondestructive evaluation in the thin layer media.
