冲击响应谱频率特征值法研究

STUDIES OF THE SPECIFIC FREQUENCY METHOD USED IN THE ANALYSIS OF SHOCK RESPONSE SPECTRUM

本文以几次地下核爆炸实测波形为例,分析了响应谱的特点,建立了计算响应谱频率特征值的经验公式,介绍了绘制冲击响应谱的频率特征值法。对特定条件下的冲击响应谱可按该法绘制。

In this paper, several real measuring waveforms induced by underground nuclear explosions are taken as specimens. By numerical method, the spectra of theselreal waveforms are obtained. We define the frequency corresponding to maximum spectrum value as the specific frequency. The main characteristics of the response spectrum are: (1) Normal displacement spectrum (ND) approximately equals 1 for low frequency and decreases with increace of frequency. Theoretical specific frequency of No theoretically equels to zero. (2) f1 is the specific frequency of the normal velocity spectrum (Nv). When f <f1, Nv increases gradually: when f>fi, . Nv decreases abruptly. (3) Normal acceleration spectrum (NA) increases with f when f>f2,. NA decreases vibrationally.f2 is the specific frequency of NA(4) For system with low damp (ξ≤0.5), the spectra of the displacement velocity and acceleration (SD. Sv and SA) coincide approximately with 3-axial spectra. which can be divided in to 3 parts by f1 and f2. When f≤f1,the spectra are constant in SD coordinate; when f1<f<f2;. the spectra are constant in Sv coordinate:when f≥f2 the spectra are constant in SA coordinate. (5) Specific frequencies f1 and f2 vary with explosion yield, distance from explosion point and the behavior of the medium. Empirical formula to calculate f1 and f2 are established.On the basis of above characteristics, the specific frequency method for drawing response spectrum is presented. This method has some advantages over the 3-coefficient method The shock response spectrum under particular conditions can be obtained by this method.