Measurement of pressure change of elastic moduli of materials constituting the earth's interior

将共振法中一种新的数据采集方法--FT法应用于实际，将脉冲信号输入到采样点，采集响应波形作为数字时间序列数据，通过傅里叶变换得到频谱。实验结果表明，在适当的脉冲宽度下，sinx/x型脉冲能产生理想的频谱;在氦气压力下，对具有样品-气腔-容器组件的球形钢样品，测量了本征频率的压力变化，最大压力可达100 MPa。获得了三种环形模式0 T4、1 T1和0 T5以及三种球形模式1 S2、1 S3和1 S4的压力频率导数 *f/*P的数据。环模的f/P直接得到刚性的压力导数G_0 '= 2.0（1）.为了减小球模的f/P对体积弹性模量K_0'的压力导数，将样品-气体-空腔容器系统看作一个球形三层结构，用DISPER 80软件计算了本征频率随压力的变化（Saito，1988），给出了K_0 '的各种值。将计算的 *f/*P与测量的比较，我们得到K_0 ′ = 8-9。这比忽略球模与测深之间的耦合而减小的K_0 '= 4-5的值大一倍。这一结果表明，在由球模的 *f/*P约化K_0 '时，必须把样品组件看作球形三层结构。通过降低K_0 '的研究成果，建立了测量各向同性固体弹性模量压力导数的新方法--空腔谐振法，并对压力介质和空腔容器材料--稀有气体和WC合金的弹性性质进行了加压测量，并将其用于球模分析。

A new data acquisition method, FT method, in the resonance method was put into practical use, where impulse input is fed to the sample and the respondent wave form is acquired as digital time series data, and the spectrum is obtained as Fourie transform. It was found the sinx/x-type impulse with suitable pulse width yields desirable spectra.For a spherical sample of steel with the sample-gas-cavity container assembly, the pressure changes of eigenfrequencies were measured up to 100MPa under helium gas pressure. The data of pressure derivative of frequency, *f/*P,were obtained for three toroidal modes, 0T4,1T1 and 0T5, and three spheroidal modes, 1S2,1S3 and 1S4. The *f/*P's of toroidal modes yields immediately the pressure derivative of rigidity, G_0'=2.0 (1).In order to reduce the pressure derivative of bulk modulus K_0' from *f/*P of spheroidal modes, the sample-gas-cavity container system was regarded as a spherical three-layd structure, and the eigenfrequencies were computed as a function of pressure by means of DISPER80 (Saito, 1988), asuuming various values of K_0'. Comparing the computed *f/*P with the measured one, we have K_0'=8-9. This is twice as large as the value K_0'=4-5 which was reduced by neglecting the coupling between the spheroidal modes and the soundings. This result demonstrates that it is necessary to treat the sample assembly as a spherical three-layrd structure in the reduction of K_0'from *f/*P of spheroidal modes. Through the present achievement to reduce K_0', the cavity resonance method has been established as a new method to measure pressure derivatives of elastic moduli of isotropic solids.Elastic properties of rare gases and WC alloys, the pressure medium and the material of the cavity container, were measure under pressure and used in the present analysis of spheroidal modes.