Cosmos Help

[crapshooter]

Hello everybody, first i'll say that i'm new to solid works-about 2 months. I'm new to Cosmos, new to CAD and i'm not an engineer. So now that you know who your dealing with. I'm analyizing an automotive connecting rod. The particular analysis i'm currently doing is a tension load. What i did was restrain the big end, insert a wrist pin and applied the load on the wrist pin. I thought that was the best way. The deformation is very exaggerated. I bought a book on the program and it says the exaggeration can be changed but doesn't tell me how. I'm looking for a realistic analysis or deformation and i would also like to get the rod to break. Can anyone tell me how to change the deformation to make it more realistic.

Thank You

 

[Mandrake22]

I'll assume that you are running CosmosWorks since the CosmosXpress that is bundled with Solidworks doesn't allow deformation scaling.
I don't have Cosmos here at home but somewhere close to the point where deformation is displayed is a dialog that allows you to enter a scale value.
Take a look in the help.
In any case, the actual deformation values are what I would be looking at.

 

[rtmpxr]

Right click the StressPlot -> Edit Definition... -> You'll find there a Settings tab where you can change the deformation factor.
About on "get to break" I don't think you can do it in Cosmos or I'm not aware of this feature in it. You must use the large deflection (eventually), large strains options and Kirchoff stresses. Also you must input the "true strain- true stress" curve and not the "engineering" curve as usual, or to use a strain rate constitutive law. Ansys or Abaqus can deal with such things. However, I don't see your point in doing a such analysis. There are other fields which need this but in your case you must "watch" to not exceed the yield stress, this is the goal. The "Factor of Safety" plot is very good in this sense. Overpassing the yield stress threshold will induce a permanent strain and your rod will loose its functionality.

Hope that Help.

 

[crapshooter]

Mandrake22, thank you. I'am using Works. This test is just a beginning for me. What i'm trying to do is find the weak spots or locations of the rod. I started this project with the idea of improving the rod, lighter or stronger. What would you recommend i should look at? Thank again.

rtmpxr, Thank you. I will mess around with it tonight. Basically i was wanting to break the rod to see or get an idea of what a failure would look like. Most of the tests i have done i inputted a higher load than i thought the rod would ever see just to see how it would handle the stress. As i have already made obvious i don't know exactly what i'm doing so this is a good learning project. Thanks again.

 

[ShaggyPE]

crapshooter,
good questions. The actual deformation of the part under real world conditions would be invisible to the eye. That is why Cosmos scales the deformation. I believe one of the other posts tells you how to change the scaling to make it less exagerated. However there is an option to turn deformation scaling off entirely.

The way you know if a part will fail using FEA is to find the stress in certain areas of the part. If that stress is greater than the "yield stress" of the material, then it will fail. By fail in don't necessarily mean break, but it will stretch some small amount that is too much for it to go back to its original position when the force is removed.

Look into the factor of safety plot after you run your simulation. This will tell you your weak areas. Areas greater than 1 are somewhat safe (greater than 2 or 3 would be more desirable). Areas less than 1 don't stand a chance.

The most critical thing about FEA is applying the proper forces. If you don't know what sort of forces the Conn-Rod will be exposed to, you are shooting in the dark.

 

[crapshooter]

Thanks Shaggy18vw, i understand about applying the proper forces. That's why i'm here asking questions,hoping to get input from some experts. What about a cyclic load like the rod actually sees during operation. Is there a program that will perform a cyclic load? Should i be looking at finding someone with a better program for this analysis?

Thanks for explaining the deformation reasons, makes sense.

 

[rtmpxr]

To optimize your automotive connecting rod see the "Shape Optimization" tutorial from COSMOSWorks (this is an add-on to COSMOSWorks, so check out the license before). It shows you all the steps to aquire your goal. I believe this is what you are looking for from the begining.
For cycle loading you must use the fatigue analysis. This is a feature of COSMOSWorks Advanced Professional bundle.

 

[crapshooter]

Thanks for the help. I did some more analysis last night after adjusting the deformaiton scale. As far as a tensile load, it showed me what i was expecting to see. I will try the other tests tonight. Thank again.