Single degree of freedom system/equivalent mass

In summary, Comsol can be used to model a simple truss and generate a frequency response that resembles a single degree of freedom system. From this data, one can determine the spring constant, damping, and equivalent mass of the system and plot the frequency response for an ideal system with those parameters. If the resulting curve is a good fit to the one produced by Comsol, it is possible for the equivalent mass to be greater than the mass of the truss and applied load. This may indicate a mistake in the modeling process. It is unclear if Comsol uses an assumed deflection form to approximate the lowest mode vector or if they have another method.
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CWatters
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It's possible to use Comsol to model a simple truss and the resulting frequency response looks like a single degree of freedom system. Using that data you can calculate a value for the spring constant, damping, and equivalent mass of the system etc and plot the frequency response of an ideal system with those parameters. Let's say you get a curve that's a good fit to the curve Comsol produced.

Is it possible for the equivalent mass to be greater than the mass of the truss and an applied load mass? Or would that indicate you have made a mistake?
 
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I don't know anything about Comsol, but most attempts to model a structure as a single degree of freedom are based on approximating the energy using an assumed deflection form to approximate the lowest mode vector. Is this how Comsol works, or do they have something else going on?
 

1. What is a single degree of freedom system?

A single degree of freedom system is a simplified model used in structural and mechanical engineering to analyze the dynamic behavior of a system. It consists of a single mass connected to a single spring and damper, representing the mass, stiffness, and damping of the entire system.

2. What is the equivalent mass in a single degree of freedom system?

The equivalent mass in a single degree of freedom system is the total mass of the system, including the actual mass of the object and any additional masses that may be present, such as attachments or added loads. It is used to simplify the equations of motion for the system.

3. How is the equivalent mass calculated in a single degree of freedom system?

The equivalent mass is calculated by adding the actual mass of the object to the mass of any additional masses present in the system. For example, if a 10 kg mass is attached to a 5 kg object, the equivalent mass would be 15 kg.

4. What is the significance of the equivalent mass in a single degree of freedom system?

The equivalent mass is significant because it allows engineers to simplify the equations of motion for the system, making it easier to analyze and understand the dynamic behavior. It also helps in selecting appropriate springs and dampers for the system.

5. How does the equivalent mass affect the natural frequency of a single degree of freedom system?

The equivalent mass has a direct impact on the natural frequency of a single degree of freedom system. A higher equivalent mass will result in a lower natural frequency, meaning the system will vibrate at a slower rate. This relationship is important in designing systems that can withstand certain frequencies without experiencing resonance.

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