# Tutorial: How To Obtain Relative Accurate Results From Stress Analysis in Autodesk Inventor

Introduction:

It is important to understand that the following tutorial will not give you the deep meaning of Finite Element Analysis.

Nevertheless, you will realise that all these FEA analysis uploaded by GC users present an approximation of the right solution (if there is one!).

Sometimes this approximation can be good sometimes BAD... and sometimes TOO BAD!

(S.-it happens all the time so... don't put too much trust to anybody even me ;P)

Furthermore you will understand that the workflows that has been introduced to you through relevant tutorials and YouTube regarding FEA Analysis are introductory, thus are not presenting the full story.

In addition you will see that the most important point in FEA, "from a solution point of you", is a converged solution obtained for a tiny error as that of 2% to 10%.

(This percentage varies to even lower values according to application).

The above statement of course assumes that you are confident to specify the right constraints and loads according to your problem (equally important).

This tutorial has reference the book below that simplifies what you need to know for a converged solution.

"Mastering Autodesk Up and Running with Autodesk Inventor Simulation 2011",

At these point I hope to made clear that there is no Right or Wrong answer in FEA Analysis BUT... a more or a less accurate prediction that reflects to the reality. That means that you run a simulation based on some VALID THEORY and you HAVE TO COMPARE with EXPERIMENTAL results.

Therefore no experimental results... no evidence how valid is your prediction.

If you are looking to dig deeper in FEA, more academic books are recommended.

But speaking to the guys that, in the end of the day, want to be confident about their results, the above book is helpful enough...

Disclaimer:

The title of the above book is used for reference and not for promotional purposes as there are much newer editions. This tutorial targets certified engineers that have the basic knowledge to judge their results. However they never had the chance to get introduced with specific sections of stress analysis settings in Autodesk Inventor.

### 5 Answers

FEA is not a simple mathematical operation.

Instead it is a computer-based iterative numerical technique along with inevitable discretization errors, as a function of elements.

Therefore these errors can be reduced by...

specifying more elements (H-refinement)

or

employing a higher order of polynomial at each iteration (P-refinement).

Effectively more computational power is required to solve complex shaped geometries with high dense mesh (Elements).

But how dense should be my mesh to get appropriate results without wasting hours on simulation ???

This is the Golden Question!

... There is a criterion for that, called Converged solution...

In plain words the mesh does not need any further refinement (denser mesh) as long as the solution is "Converged".

The solution is assumed to be "Converged" when the results of the polynomial eq. does not change according to a prespecified tolerance e.g. 10% Good Results, 0.1% Great Results.

So, let me share some information how to manipulate the mesh for a model along with three examples.

As a conclusion we will enhance your confidence regarding the results you get, whether are relatively accurate or not (Low Percentage of Discretization Errors) without wasting hours on simulation!!!

Don't Forget the simulation results are nothing without any experimental results to compare with.

Answered with a tutorial: https://grabcad.com/tutorials/tutorial-how-to-obtain-relative-accurate-results-from-stress-analysis-in-autodesk-inventor