Learning Forum

[Basit Khan]

I'm using ANSYS modal analysis to understand the stiffness and vibration behavior of two different spring designs. While modal analysis provides valuable insights, I'm more interested in estimating the damping ratio of each spring design. I understand that ANSYS might offer features like Rayleigh Damping for this purpose.

My Questions:

1. Does my ANSYS version 2021R1 have functionalities for estimating damping ratios during modal analysis? If so, could you point me towards the relevant documentation or tutorials?
2. 2. If using Rayleigh Damping, are there any recommended approaches for selecting the appropriate damping coefficients (alpha and beta) for my wave spring models.
3. Additional Information: • My spring models were created in SolidWorks and imported into ANSYS. • I'm defining appropriate fixed supports based on the intended application • I'm using a refined mesh for accurate modal analysis results. Thank you for your time and assistance! Sincerely, Basit Khan

[peteroznewman]

You have the data flow backward.  Ansys Mechanical doesn't estimate damping ratios. Physical testing measures damping ratios and those measured values are used as inputs to the Ansys model that estimates the system response to vibration loads.

Once you measure a damping ratio, there are equations to calculate the Rayleigh Damping coefficients, but if you use Modal Superpostion methods, you can use the damping ratio directly and use a different value for each mode.

[Basit Khan]

Actually I am  working on a project involving the dynamic analysis of wave springs( 2 different design). I will obtain the damping ratio from experimental measurements using methods like the logarithmic decrement and half bandwidth method.

But I am planning to perform both modal and random vibration analyses in ANSYS to further understand the damping and stiffness characteristics of the wave springs. I have a few questions regarding the relationship between the experimental damping ratio and the results obtained from numerical analyses:

1. How can I relate the damping ratio obtained from experimental measurements to the damping characteristics inferred from modal and random vibration analyses in ANSYS( Which Damping characteristics i would get from thes two analsys - MODAL & RV?

2. Are there specific parameters or results from modal and random vibration analyses, such as natural frequencies, mode shapes, PSD plots, and RMS values, that can directly correlate with the experimental damping ratio?

3. How can I validate the accuracy and reliability of my numerical simulations using the experimental damping ratio as a reference.

I would appreciate any guidance, insights, or suggestions on how to approach this comparative analysis and validation between experimental and numerical damping characteristics in ANSYS.

Thank you in advance for your help.
-Basit