Need an help in Modal Analysis

In summary, the conversation discusses a person's urgent need for help with a Modal Analysis for an audio system attached to an Instrumental panel in a car. They used ANSYS 13 version software and a SHELL281 element for meshing, and extracted 12 modes using the Black Lanczos method. However, they encountered an issue where the first six frequencies had zero values and they were unable to interpret the results. The other person in the conversation suggests that this may be due to the structure being a free body and recommends assuming that the panel is fixed rigidly for more accurate results. They also question why a free-free modal analysis was performed and the importance of considering constraints.
  • #1
bhartish
26
0
Need an urgent help in Modal Analysis

I am doing an modal analysis of audio system attached to an Instrumental panel in a car using ANSYS 13 version software. I have used SHELL281 element for meshing and Black Lanczos method to extract the modes. This shell element has six degrees of freedom. I Have extracted 12 modes but the first six frequencies I am getting zero value. I am not able to interpret the results. request anyone to guide .
 
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  • #2


The first 6 frequencies will be zero if your structure is a free body. They conrrespond to the 6 rigid body motions of the structure (3 translations and 3 rotations).

It would probably be better to assume the panel is fixed rigidly at the points where it is connnected to the rest of the car.
 
  • #3


Hi,
Why did you perform a free-free modal analysis? Why it is useful for? I mean, you should always have into account the constraints, shouldn't you?
 

1. What is Modal Analysis?

Modal analysis is a technique used to study the dynamic characteristics of a structure or system. It involves analyzing the natural frequencies, mode shapes, and damping ratios of a structure in order to understand its response to different types of excitation.

2. Why is Modal Analysis important?

Modal analysis is important because it allows us to understand the behavior of a structure or system in response to different types of loads or forces. This information can be used to improve the design and performance of structures, and to identify potential problems or failures before they occur.

3. What are the different types of Modal Analysis?

The two main types of modal analysis are experimental and numerical. Experimental modal analysis involves physically measuring the dynamic characteristics of a structure using sensors and data acquisition systems. Numerical modal analysis involves using computer simulations and mathematical models to predict the dynamic behavior of a structure.

4. How is Modal Analysis performed?

Modal analysis is typically performed by exciting the structure or system with a known input, such as an impact or a shaker, and measuring its response using sensors. The data is then processed using specialized software to determine the natural frequencies, mode shapes, and damping ratios of the structure.

5. What are the applications of Modal Analysis?

Modal analysis has a wide range of applications in various industries, including aerospace, automotive, civil engineering, and mechanical engineering. It is used for product development, structural health monitoring, and failure analysis, among other things.

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