Learning Forum

[deepesh.p.gurdasani]

Can change in density have any effect on modal analysis ? I do understand if you change the material, it could have effect but here I mean to ask 'change in density' and keeping other material properties constant.

Thanks in advance 

[Sai Deogekar]

Yes, change in density will affect the natural frequencies of a structure and hence affect the results of a modal analysis.

In FEM, natural freequencies are calculated by solving the equation: det [K - omega^2 * M] = 0 (det - determinant, K - stiffness matrix, omega - natural frequency, M - mass matrix). Changing density will change the mass matrix, M, and hence affect the natural frequencies, omega, even if all other material properties are unchanged.

You can find more explanation about the above equation in lesson 3 of this course: Modal Analysis | Ansys Innovation Courses

You can also learn more about Modal Analysis in Ansys Mechanical here: Modal Analysis in Ansys Mechanical | Ansys Courses

Hope this helps.

[deepesh.p.gurdasani]

But then when we use point mass in modal analysis, here point mass doesnt have any material properties. So, should this change results significantly when compared to original body being present in analysis?