Mechanica Results

[78finn]

I have a simple Mechanica model setup (using Mechanica Light).

The model consists of a 3.0mm thick, mild steel bar / 500mm in length.
The bar is constrained / fixed at either end and has a 30KG weight /
down force applied at its centre.

I understand how to setup the analysis, the problem I am having is
understanding / interpreting the results that Pro E presents me with.

The result I'm most interested in is the maximum displacement. I was
expecting a result in mm.

Instead Mechanica presents me with a spectrum of results in the form of
a color coded chart. This chart indicates a Min & Max displacement.

Min: 0.000e+00

Max: 5.037e-04

My questions is, what does this actually equate to?

Obviously the Min result shows zero displacement to the bar, but I'm
confused by the Maximum displacement result.

Does the 'e-04' mean that I am to move the decimal point back 4 places?

This would indicate a maximum displacement of 0.0005mm.

Is this correct?

Any help you can be with helping me interpret these results would be
very much appreciated. If it would be helpful to have the file I'm working
on, please let me know and I will upload the file - I'm running Pro E
WF5.0

 

[78finn]

<a target="_blank" href="uploads/78finn/2011-08-05_010324_Bar_results.zip" target="_blank">2011-08-
05_010324_Bar_results.zip</a>

Here is the results file (rwd file) for the model that I am trying to
understand. Again if anyone can be of any help, I would really appreciate it.

 

[wanqichao]

 

[78finn]

This does not seem right though - can anyone else please confirm/help?

 

[Ray Ellender]

Calculate the expected deflection using a hand calc (formulae available in your engineering degree notes or 'Roark'). If it doesn't match, you either didnt load it correctly (probably wrong units - you need Newtons), or the way you have actually constrained it is not doing what you had in mind. It sounds like you need to go on atraining course, and given your lack of knowledge of scientific notation, an engineering degree course if you haven't done one, to understand better how to do stress analysis.

 

[78finn]

Hi there Ray,

Thanks for the feed back, what I'm really trying to understand is what the
result: Max: 5.037e-04 actually equates to?

can you tell me what the 'e-04' means?

This alone would be of great use to me!

The way the model is setup and constrained is correct, that I'm certain
of. Whilst I'm not certainly not an engineer, I do have a basic
understanding. I agree with you though...there is no substitute for formal
or on the job training. But it would be really good to just a get a few
pointers on here to help my understanding of the results I'm looking at.

 

[Atropos89]

e-04 just means x10^-4. It's exponent notation.


EDIT: http://en.wikipedia.org/wiki/Scientific_notation#E_notation
Edited by: Atropos89

 

[78finn]

Hi there Atropos...thanks so much for the link! This is so helpful!!!

 

[srieger]

The range is the range of displacement throughout the part. Max is the maximum displacement at a given point. The entire bar isn't going to move if the ends are constrained. The forces will cause it do deflect most at the point of the force and less further from the force. This is what the color code represents.

 

[78finn]

Understood...

I must have something setup incorrectly I think. I know how to do the engineering calculation to work out the max deflection of a bar with simply supported and fixed ends - very simple really. However, the results I'm getting from a method I know to be correct are different to the results in Pro E. Not hugely different...but enough to be of concern.

Does anyone know of any good tutorials floating around on the web for mechanica light and mechanica?

Thanks for everyone's help

 

[indigo2]

There are several resources available.
First, i'd suggest the Help Topic Collections from PTC's own website. There are several manuals in PDF format, one of which is specific to Mechanica. Even though there is no WF5 specific version, the material is still relevant, and covers many aspects of using the tool.

Second is the Verification Models. This is an option selected during the installation of Mechanica. These models are of the independent Mechanica format, but the results from these simulations are still readable in integrated mode. There are many models to choose from, covering all aspects of Mechanica.

The combination of these two sources will help with your understanding of the toolset, and give you a better level of comfort on the accuracy of your solutions.

That being said, none of this is intended to replace actual training on the tool. This was intended to increase awareness of some of the resources available to you from PTC.

Hope that gets you started.

-tsl

 

[srieger]

One thing to keep in mind is that Mechanica uses a different element type that produces more accurate results. There is also the long and short analysys which may produce minimally differing results.