Reliability simultaneous beam results

Simulation Generality
1

Hi all

I wonder about the reliability of the results on beam simulation in SolidWorks.

Let me explain, I did a simple test on a classic beam:

Rectangle tube of 200 x 100 x 10 with a length of 3000 mm in S 235.

I fixed the 2 external connections,

and I split my beam in the middle into two bodies to have a central connection to which I apply a force of 80,000 N.

The results obtained are:

- Maximum stress 118.5 Mpa

- Max deflection 2.3 mm

By doing the calculation manually  I find:

- Maximum stress 237 Mpa

- Max deflection 8.9 mm

Can someone explain these differences in results to me?

Thanks in advance

Have a nice day

2

My first question is that you split

the dif is double in Mpa,

Maybe due to the splitting?

Are your outdoor connections free (slippery) or fixed (fixed point)?

Maybe it would give this difference?

See this link among others

http://jean.lamaison.free.fr/flexion.html

 

2 Likes
3

The results of your simu do indeed seem strange. How are your 2 external connections put? 

4

My two external connections are fixed.

And I split the beam to have a connection and be able to apply the central effort,

for a force can only be applied to a beam on a connection, a vertex or a complete body.

How do you apply a force to the center of a beam?

5

See this link to apply a force

https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjr0MvGztvJAhXEcA8KHcrIAGEQtwIIIDAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DvxczDuuejso&usg=AFQjCNE1x7No2NzziHgdCp6fEYF8hrn4mQ&sig2=AtsCB5m-SvEdP1UolRBo8A

1 Like
6

Yes I know the method with a dividing line but it only works in volume,

Now my tube is beam.

7

The calculation you make by hand is consistent in the hyptohesis of a beam on 2 supports. At the extremities, the normal rotation in the plane is free.

If the ends are recessed, the stress and deflection will necessarily be lower. Now I don't have the formula in mind anymore but the SW result is not necessarily inconsistent.

 

8

Personally, I have never managed to master the calculation in beam or shell under SW.

The good old volume calculation works in 95% of cases (unless you are on a framework or with very large length/section ratios). The interest of the volume is that at least you have an idea of what happens at the junctions and embeddedness (which are the critical points usually). So it's sure that you get a fair of knots/elements but with modern PCs generally you get a result in less than 5 min.

Try to do the math on your piece in volume, it should be okay (although you're a bit long).

Your result seems to correspond to the case where your end points are fixed and with a central joint (if the ends of the beam can't get closer to the center, it necessarily reduces your arrow to the center). In beam I don't even know if you can simulate the flat support of your beam at the two ends.

9

Hello

Thank you all for your answers.

Indeed, as Chamade and Froussel say, I was wrong in my interpretation.

Indeed, I fixed my two extremities instead of creating two supports.

So I created imposed displacements with reference geometries

by locking the translations according to Y & Z, thus leaving the beam free in translation according to X.

The results are quite satisfactory:

Maximum stress 237.1 Mpa for 237

Max deflection 8.676 mm for 8.9

Issue Resolved

Have a good day everyone

10

Have they all told you your external fixing?  ;-)

Solve the question about the answer that best fits

have a nice day @+