Simple Fequency Experiment On Bone (Advice Needed Please)

[tom1362]

"Simple" Fequency Experiment On Bone (Advice Needed Please)

Hi All,

Great Site.

I am trying to find the Resonant Frequency (Natural Frequency) of a Sheep Tibia using an Electromagnetic shaker with an Impedance Head attached as well as an Accelerometer mounted on the opposite end of the Bone to monitor the output repsonse.

I am currently not having great luck in acheiving what i am looking for.

I am holding the bone in a Free-Free end condition, and with a Single Degree Of Freedom. Exciting one end of the bone using the shaker. Obtaining the the response at the opposite end. I was hoping to be able to calculate some sort of transfer function for the Bone (system)

I am using Bruel&Kjaer Labshop as my Hardware & Software which displays both the Time & Frequency domain on screen as i vary the excitation signal (Stepped Sine Wave) .

Is it possible to Calculate this Transfer Function? / Find the Natural Frequency ? / Observe when the bone is appraoching its Natural Frequency on screen ?

Most appreciative for any Help

Kind Regards

 

[FredGarvin]

The easiest I can think of is to have a running FFT while you are shaking and watch for the peaks. If you do indeed hit the first bend frequency of the bone, that is where you would see it.

Is it possible that you are getting dampening from the inner part of the bone? Are you sure you are putting enough energy into the bone to really excite the modes? Also, have to proven your experimental set up with something simple like a cantillever beam to make sure your data acquisition system is working properly?

 

[minger]

Agreed, the structure of bones is extremely complex. Have you tried something simple like plink testing it?