SolidWorks Simulation:黑胶唱片机盖支撑垫的模态分析

宇宙立方

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Most audiophiles say that there is something warmer, richer, and better to the sound a vinyl record reproduces, especially compared to modern digital media. Not having listened to an album since I was young, I figured it was time to see what all the talk was about. I asked my father (long time high-end audio enthusiast) to get out his vintage 1973 JVC VL-5 turntable so we could give it a listen.
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Note: This picture is post installation of the new feet.

After all these years in storage the turntable was in great shape. Everything worked perfectly except for the vibration isolating rubber feet. Out of the four feet, three had the material break down, leaving them brittle and cracking with large sections missing or crumbling. Obviously this was not good news as the turntable needs to sit level when in use

I searched the internet for replacements but could not find any that were suitable. The next step was to make our own. Using Solidworks, my father reverse engineered a new set of feet for the turntable. After a few design iterations, the new feet were a little more stout than the originals. Thanks to SOLIDWORKS SImulation, the new feet exhibited the mechanical properties we desired.

We did not know the type of rubber used in the original foot. This was not a problem as we usedSimulation Premiumand the Nonlinear material models to determine a relative stiffness. By physically testing the original foot under a 2.5 lb. vertical load we measured a 0.1 in. displacement. Using Simulation and varying the material properties we found that a Shore Value of 70, gave a 0.095 in.corresponding vertical displacement. Feeling confident in the design the next step was to test for vibrational characteristics.

The turntable operates at 33 1/3, and 45 RPM. This equates to 0.556, and 0.75 Hz respectively. SOLIDWORKS Simulation Professional made it possible to test the resonant frequency of the design. The analysis results predicted the lowest resonant frequency at 16.32 Hz. This is well above the induced vibration due to the turning motor and drive mechanism, and lower than the 20,000-20 Hz most receivers output.

Next we turned to theStratasys Polyjetline of printers that delivered an amazing print. The Polyjet printed a 70 Shore value model that behaved just like we expected. Not only did the print physically work, it looked great too.

xiaobing86203

请教大神，你这个模态分析，标准是什么样的？是否看第一阶模态频率值？

陈小困

xiaobing86203 发表于 2017-5-16 13:13
请教大神，你这个模态分析，标准是什么样的？是否看第一阶模态频率值？

+ u* A/ R8 @9 S( j' H按照楼主的意思，lowest resonant frequency at 16.32 Hzlower than the 20,000-20 Hz most receivers output.
. K" m0 f' b+ Y+ W' j* v( p第一阶不共振，就不考率其他阶了？ 还是说要分析整个装配体？还望大神指点下
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宇宙立方

其实不是说一般取前5阶.根据不同的对象和边界条件,取得阶数都不同.对于没有约束的对象,前6阶为刚体移动模态,频率为0；而对于有约束的对象,则没有刚体模态.各阶振型的话就是各阶的振动形态,有横向振动,扭转振动,拉伸振动,这些需要你观察振型来判断.你想理解模态必须去看一些振动学的书籍.简单的讲物体的实际振动是各阶模态的叠加效果.物体理论上有无穷阶模态,振动是这无穷阶模态的叠加.但是实际上各阶模态对系统振动的贡献度不同,一般前几阶比较大,越往后越小,所以一般截取前面的模态.