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首页> 外文会议>International Symposium on M~3D III: Mechanics and Mechanisms of Material Damping Norfolk, Virginia, 15-17 Nov. 1995. >Amplitude-dependent damping in YBCO ceramics between 6.5 K and 290 K
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Amplitude-dependent damping in YBCO ceramics between 6.5 K and 290 K

机译：YBCO陶瓷中6.5 K至290 K之间的振幅相关阻尼

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摘要

Nonlinear acoustic effects in yttrium-barium-copper-oxygen (YBCO) ceramics with different grain sizes were investigated by means of the piezoelectric ultransomic composite oscillator techniqe (PUCOT) at frequencies of about 100 kHz, corresponding to longitudinal resonance vibration. It has been shown that the acoustic parameters (decrement and resonance frequency) exhibit hysteretic behavior at temperatures in the range between 6.5 K and 290 K. Irreversible changes occurring in these acoustic parameters during measurements of their amplitude dependence at 6.5 K were found to disappear as a result of thermal annelaing at 65 K. Furthermore, an unusual crossover hehavior in the amplitude dependent damping curves obtained al low temperatures has been observed for the first time. This crossover effect depends strongly on grain size and disappears at temperatures above 100 K; it has never been, so far, observed at room temperature. It appears that the crossover effect is related to an unusual time dependence of the nonlinear damping: at high vibration amplitudes, the decrement decreases, simultanelusly with a decrease of the resonance frequency, that is, an increase of the Yougn's modulus defect. This observation can be understood by considering separately the effects of high-amplitude vibration on the acousu0014ic parameters at both low and high strain amplitude.
机译：利用压电超音波复合振荡器技术（PUCOT），在大约100 kHz的频率下研究了不同晶粒尺寸的钇钡铜氧（YBCO）陶瓷中的非线性声学效应，这与纵向共振振动相对应。结果表明，声学参数（减量和共振频率）在6.5 K和290 K之间的温度范围内表现出滞后行为。在测量其在6.5 K时的振幅依赖性时，这些声学参数发生不可逆变化，随着这是在65 K时进行热退火的结果。此外，首次观察到在低温条件下获得的振幅相关阻尼曲线中的异常穿越现象。这种交叉效应在很大程度上取决于晶粒大小，并且在高于100 K的温度下会消失。到目前为止，从未在室温下观察到过。似乎交叉效应与非线性阻尼的不寻常的时间相关性有关：在高振动振幅下，减量随着共振频率的降低而减小，即，Yougn模量缺陷的增加。通过分别考虑高振幅振动在低和高应变振幅下对声参数的影响，可以理解这一观察结果。

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