In my previous article, I asked to my newsletter subscribers 2 questions to see who knew how to perform a dynamic analysis of the following marine refrigeration machine:

￼The questions were:

**Question 1:**

What steps would you take to identify the main vibration characteristics of the marine refrigeration machine in the previous image?

**Question 2:**

What would be the main challenges you can expect to meet in such a complex FEA analysis?

Ok, now, take the time to think, don’t read the answer below that line…

**Answer:**

Congratulation, Erkan Talay, you nailed perfectly the answers to the simulation problem! I am impressed.

￼

Let’s analyse Erkan’s answer together…

Do you see the « key foundational pieces of knowledge » I was talking about?

￼

Step 1: Calculating the natural modes.

A modal analysis can help us here to identify the modes of vibration of this system.

Read more about modal analysis here

## Step 2: Calculating the frequency response

A modal analysis only gives us the natural frequencies of vibrations, but it doesn’t provide the actual dynamic response to a given dynamic excitation. That’s when we need to use frequency response analysis.

Read more about frequency response analysis

## Step 3: Dealing with the peaks of the frequency response curve by improving the minimum structural mode

In FEA, what is really important is the data you actually get, because data is what tells you where you can improve your model or where you have a problem in your design.

Now… you need of course to have accurate results in order to be able to make some conclusions… and this is not necessarily obvious…

Read more about the dangers of bad accuracy in FEA results

## Step 4: Consider the transient behaviour of the cooling gas flow

Now we are getting to the advanced stuff ;-)

Simulating the flow inside the machinery along with temperature can be really challenging.

First you have to understand heat transfer, secondly, you have to understand CFD (Computational Fluid dynamics).

Read more about the physics of heat transfer here

**The thing is…**

If you want to simulate anything more complex than a plate or a beam, chances are that you will need this « key foundational knowledge »… along with experience & practice of course

Yes, you will have to learn and refine your skills to understand all the details. But once you do, everything will become easier ;-)

The other good news is that you don’t need to start right away with such a complex model.

In fact, whenever I start to analyse something rather complex, I like to simplify the model a maximum in order to be able to nail down the most important choices you’ll have to do right from the start.

## Want to know more about dynamic analysis?

*Take the pill and follow the white rabbit into the rabbit hole ;-)*

￼

**Read those articles to understand better dynamic analysis:**

Read my article explaining about modal analysis

Read my article explaining about frequency response analysis

Read my article explaining the difference between steady state and transient response

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Thank you for reading!

**–Cyprien “Understanding is dynamic” Rusu** ;-)

Mahesh Gaikwad says

This one is your best article

Avijeet S says

Hello Sir,

Hope you are doing Fine. I would like to discuss my query about cylindrical support. I am doing a simulation of the clutch assembly where a clutch assembly is mounted with the shaft and shaft is rotated by a gear. There are two bearing which connects and hold the shaft. I just want to confirm at the place of bearing, I have taken cylindrical support and which option I should keep free or fixed from radial, axial, and tangential. I have keep all three options as fixed. I also want to know, how to add oil temperature(120 Celcius) on the clutch plates in the simulation. I have taken 120 degree celcius environment temperature on the plats in the clutch assembly and rest of the parts are at normal temperature.I am performing the structural transient analysis and there are four loads: rotational velocity in rpm, torque, springs forces and gravity. Now, i would like to know this FEA setup is fine for transient structural analysis. I am I am eagerly waiting your response.

Thanking you

Vaibhhav says

Thanks a Ton for this article. I am looking forward to have more such articles.