How can a part's geometry be used for damping or to reduce vibration?

1. Jun 5, 2014

1muffin

Hi,

So basically I am wondering how can you increase damping within a part, just by altering its geometry. I've researched this topic, but haven't yet found anything significant. Here are my main findings:

- Rayleigh Damping uses the equation: [C] = α[M] + β[K], which to me shows that mass and stiffness affect damping
- Damping constants are difficult to obtain; use of available literature and experimentation are the only ways to go

From this, I believe there is a useful link between stiffness and damping, and that I could design a part in certain ways to increase damping/reduce vibration (I understand these are very different things). For example, would stiffening a part, reduce the response of the part under excitation?

The aim for me is to develop an understanding from a design perspective as to how we can use geometry to reduce stresses in a part under dynamic loading.

Thanks in advance for any help.

2. Jun 5, 2014

AlephZero

First, decide what you really want to do. You mentioned

Increasing damping
Reducing vibration
Reducing response
Reducing stresses

Those are four independent ideas. You could invent different examples which reduce one and increase the other three.

Also, the Rayleigh damping model is just a convenient mathematical fiction.

The first step in unpicking this tangle is probably to understand the physics of how energy is removed from your design. That will probably depend on what materials are involved. Then you can start using the appropriate mathematics to model the dynamics - which might or might not be Rayleigh damping.