Stress analysis on chassis

[Anonymous]

Hello, I'm a student working on a team project to build a vehicle and we're required to do a stress analysis to make sure if the vehicle (chassis, supports, etc) can withstand the weight of the driver, etc.

The problem is that the analysis that I did doesn't seem to make any sense at all, like there was no stress between the joints, the frame bent when the applied force was only 5 kg...

The metal used is mild, steel.

I hoped someone do it for me. Thanks!

[MariaManuela]

Hi.

In order to open your assembly we need also the IPTs files.

[henderh]

Also, there isn't any simulation data saved in the posted assembly file.

[Anonymous]

I'm terribly sorry! I was in a great rush that I didn't consider that. I will attach them tomorrow (I used the PC in our lab). Sorry for the inconvenience.

[Anonymous]

Okay, here are the files. I made the tyres and the swing arms for the sake of constraining (they're not the real design).

Two tyres are in the front, and only one in the rear.

The floor is for the driver compartment (the one without are the bulkheads for motor and battery).

I simulated the stress analysis on the driver's compartment with the driver's weight of 50 kg. But the results didn't make sense.

[Anonymous]

One more attachment--I removed the FEA file because it's 12 MB (Had I realised it sooner, there will be only one attachment in the previous post)

For the simulation:

*Material:   Floor (Plywood, but I assigned Birch Wood)

                  "Wheels" (Since they're fake, I used Alloy Steel)--Fixed constraints here

                  Everything else (Mild, Steel)

*Downward Force of 500 N applied on the surface of the wood.

[MariaManuela]

Hi,

By Jimmy Yuan - Autodesk

..."Stress Analysis only supports isotropic, but not orthotropic material, such as wood which has different modulus of elasticity and poisson ratio along different directions..".
More here http://forums.autodesk.com/t5/Autodesk-Inventor/Wo​od-Stress-Analysis/td-p/2671875

Other:

http://forums.autodesk.com/t5/Autodesk-Inventor/Screw-fixings-for-wood/m-p/3305599/highlight/true#M4...

Other:

http://forums.autodesk.com/t5/Autodesk-Inventor/Stress-analysis-on-wood-material/m-p/2541810#M352135

[Anonymous]

Thanks for the reply Maria. I haven't yet learned about this isotropic/orthrotropic thing, so I looked up on that. Well, that certainly explains why the floor was bent in U-shape between the metals.

But I'm not worried regarding the wood so I assigned the floor's with steel and the ran the analysis (as shown in the picture). Why there aren't any joint stresses? Or do I have to convert the assembly into a single, whole part?

[henderh]

Hi brunalz,

<<The problem is that the analysis that I did doesn't seem to make any sense at all, like there was no stress between the joints, the frame bent when the applied force was only 5 kg...>>

  Viewing the image from the last post, this is the correct result display.  By design we show a highly exaggerated deformation so it can be easily seen.  The converse is true, if we have a huge displacement (going off the screen) we'll un-exaggerate the displacement.

  Since Safety Factor result type is displayed, and the entire structure seems well below yield, all the SF results will be a uniform blue color.

[Anonymous]

---

"By design we show a highly exaggerated deformation so it can be easily seen."

I see. But I just (I apologise for being so stubborn) couldn't get rid of this worried feeling seeing the results lacking of stress gradient. I was wondering if it's possible to achieve a similar result as shown in the attachment (the picture shows the stress simulation done using Strand 7 FEA on a vehicle's chassis -- courtesy of a team from the Durham University).

[henderh · Accepted solution]

Stress Analysis can show Von Mises, Principal stresses, or stress tensor components in the cartesian coordinate system.  It's not always axial stress since it will include shear, bending, torsional, etc. stresses if present.

Inventor's Frame Analysis can calculate axial stress explicitly.

[rmerlob · Accepted solution]

Just change the scale on the color bar if you want to se a stress distribution, as it is, everything looks blue because theres a few concentrated stresses that are way higher than others,this causes color bar to default to a scale that captures the entire range in only one color.

[Anonymous]

O.K. Thanks for the helps everyone! Really appreciate it!