关于波速的有限元

semi526

请教高手：
如何利用动力学的有限元方法求波速啊？
波就是应力波，应力波在固体中传导的波速。

我把动力学方程都用纽马克方法解了，时程曲线也得了，可是不知道如何求波速。

请高手指点一二，谢谢了！

继往开来

You do not need to solve the dynamic equation to get wave speeds.
Wave speeds can be derived from modulus and mass density.

Also, you need to know the difference between vibration and wave propagation.
For SDOF vibration, no such thing as wave speed.

semi526

谢谢，非常感谢。
我的不是单自由度体系，我的是连续模型，一维的，ONE-DIMENSIONAL ELASTIC WAVE PROPOGATION 问题。

继续请教一下问题：
1》我的不是一般的材料，波速不可以直接由弹性模量和密度相除开根号求出来，
我的是MULTISCALE的跨尺度模型，微观下的类似纳米管，弹性模量由能量最小化来确定。
那么这种情况下的波速怎么确定呢？

2》还有我怎么看见很多文章中波速WAVE VELOCITY 和 WAVE VECTOR 有关呢？我的多尺度有限元模型里面什么是WAVE VECTOR 呢？我都不知道怎么从有限元模型得到WAVE VECTOR ，实在不懂。

再请指教，谢谢

继往开来

Multiscale modeling is beyond my area of study.
In a continua problem, either homogeneous or inhomogeneous, the common way is taking time histories at uniform intervals, and presenting the results in f-k (frequency-wave number) domain to get the phase velocity dispersion curve. I am not sure this is applicable to multiscale material or not.

semi526

Multiscale modeling is beyond my area of study.
In a continua problem, either homogeneous or inhomogeneous, the common way is taking time histories at uniform intervals, and presenting the results i ...
继往开来 发表于 2011-3-23 04:39

是，是的，就是这个，太好了。谢谢大师，还请继续指教一下：

f-k (frequency-wave number) 和 phase velocity 我就不知道这个是怎么得来的。我看的文章都有 f-k (frequency-wave number) 和 phase velocity 曲线。
但是，有限元方法解出来只有时程曲线啊就是 time histories ，速度，位移，加速度的 time histories 都可以解出来。我用NEWMARK法解出来了，可是f-k (frequency-wave number) 和 phase velocity 我不知道是怎么得来的。wave number在哪里啊？我都不知道怎么找。

请指教，太感谢了。

继往开来

Then you need some basics of discrete Fourier transform. Please distributed the receivers wisely to capture the frequency of your interest. If you have no background knowledge of signal processing, you do need some time to be familiarized with it.
It is not possible to fully develop the details here, but you should have a direction to go. BTW, I think you can consult some experienced ones in your surroundings. That would be more efficient.

semi526

6# 继往开来

好的，谢谢，我看看书，不懂的再请教.