Designing a System to Isolate Higher Order Modes in a Fixed-Fixed Beam

In summary, the conversation discusses a fixed-fixed beam with a distributed force and the calculation of its fundamental mode of vibration. The speaker also raises the question of how to isolate higher order mechanical modes from the fundamental mode and asks for suggestions on how to design the system. The other person responds that the best way to dampen the higher modes is to apply damping at the points of maximum amplitude. However, this cannot be fully specified until the modes that need to be suppressed are identified.
  • #1
Karthiksrao
68
0
Hi,

Suppose we have a fixed-fixed beam with a distributed force acted in between -on a part of the beam.

I have found out the fundamental mode of vibration i.e calculated the fundamental resonant frequency of the above case.

But there will be higher order mechanical modes too.. In case I have to isolate the higher order modes from the fundamental mode, how should I design the system?

Any way I can go about doing this?

Thanks
 
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  • #2
What do you mean exactly "isolate" the higher order modes? Are you trying to damp the higher natural frequencies while leaving only first mode?
 
  • #3
Exactly
 
  • #4
This question cannot really be completely answered until you know fully what you have to deal with. By that I mean, until you know what higher modes are present at significant amplitudes, the fix cannot be fully specified.

In general, however, the most effective damping of the higher modes will be that which is applied at the points of maximum amplitude of the modes being suppressed. Thus you need to find the modes that must be suppressed and plan damping accordingly.
 

1. What is the concept of "vibration of fixed-fixed beam"?

The concept of "vibration of fixed-fixed beam" refers to the study of the dynamic behavior of a beam that is fixed at both ends and subjected to external forces or loads. This type of beam is commonly used in structural engineering and understanding its vibration characteristics is important for ensuring structural stability and performance.

2. How is the vibration of a fixed-fixed beam modeled mathematically?

The vibration of a fixed-fixed beam can be modeled using the Euler-Bernoulli beam theory, which is based on the assumptions that the beam is slender, straight, and subjected to small deflections. This theory results in a second-order differential equation that describes the displacement of the beam as a function of time and distance along its length.

3. What factors affect the vibration of a fixed-fixed beam?

The vibration of a fixed-fixed beam is affected by several factors, including its material properties, geometry, boundary conditions, and applied loads. The stiffness, density, and damping of the beam material can significantly influence its natural frequency and mode shapes. Additionally, the length, cross-sectional area, and moment of inertia of the beam can also affect its vibration behavior.

4. What is the significance of studying the vibration of fixed-fixed beams?

Studying the vibration of fixed-fixed beams is crucial for various engineering applications. It helps in designing and analyzing structures to ensure their safe and efficient performance under dynamic loads. The knowledge of natural frequencies and mode shapes also aids in detecting potential structural failures or malfunctions.

5. How can the vibration of fixed-fixed beams be controlled or reduced?

There are various methods for controlling or reducing the vibration of fixed-fixed beams. These include altering the material properties (e.g. using damping materials), changing the geometry (e.g. adding stiffeners), and modifying the boundary conditions (e.g. using different support types). Additionally, active vibration control techniques, such as using sensors and actuators, can also be employed to actively suppress unwanted vibrations in real-time.

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