×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

So...how much do you guys trust Cosmos express?

So...how much do you guys trust Cosmos express?

So...how much do you guys trust Cosmos express?

(OP)
I just did an analysis on a simplified representation of a thiung we build at work. I constrained it and loaded it pretty much how it will live its life.

Now I'm no stress guy by any means.... but I guess I was a little surprised by the results. I thought the stresses would be higher than they seem to be. I guess this is good news, but I wonder if I'm being lulled into a false sense of security?

RE: So...how much do you guys trust Cosmos express?

My experience with FEA is that loads and constraints required for good answers are a bit more detailed than COSMOS Express allows.  It's probably OK as a comparative tool, but not for real quantified answers.

RE: So...how much do you guys trust Cosmos express?

CE only only good for simple parts to get a quick FEA while in the design process. If you need a full FEA, use the full Cosmos program.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP1.1 / PDMWorks 05
ctopher's home site

RE: So...how much do you guys trust Cosmos express?

The safest way is to do a physical test (if possible) & compare the results to your CE results.


Making the best use of this Forum.  FAQ559-716
How to get answers to your SW questions.  FAQ559-1091
Helpful SW websites every user should be aware of.  FAQ559-520

RE: So...how much do you guys trust Cosmos express?

Another way to validate CE is to do some simple hand calculations.

Best Regards,

Heckler

Do you trust your intuition or go with the flow?

RE: So...how much do you guys trust Cosmos express?

(OP)
I'm not looking for real numbers. I was just looking to see if my 60 gal hydraulic tank is going to fall off the truck on the highway, thus making headlines like, "Highway closed for two hours due to failed hydraulic tank. Society now hates local enigineer".

RE: So...how much do you guys trust Cosmos express?

(OP)
.....and from the sounds of it, people don't trust CE too much at all eh?

RE: So...how much do you guys trust Cosmos express?

Like any FEA program - garbage in garbage out.  FEA can be extremely complex to set up the load cases and optimizing the meshing process.  If you have a basic understanding of engineering mechanics (materual properties, failure theory, free-body diagrams) this should be an interesting problem to solve.

Best Regards,

Heckler

Do you trust your intuition or go with the flow?

RE: So...how much do you guys trust Cosmos express?

CE can be trusted, as I wrote before, only for small stuff as you design the part. Not for final FEA of a product.
I agree with Heckler "garbage in, garbage out".

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP1.1 / PDMWorks 05
ctopher's home site

RE: So...how much do you guys trust Cosmos express?

(OP)
I would hope that my degree in mechanical engineering would afford me some level of understanding of these things....which is why I'm questioning CE in the first place.

The thing I was trying to analyze is essentially cube, 24" x 24" x 32". made of 10 ga. steel. It has two vertical chunks of 1/2" x5" x5" angle about 15" long weld on the sides as mounting brackets. (as that's what we had handy in the shop). Once filled with oil, the tank will weigh about 700 lbs.

My concern was the area where the angles are welded to the tank. Sure the angles are really strong, but could the sheet metal tear near the welds?

For my purposes, in SW I made the cube. Shelled it, and added two angles. (all as a single part of course)

I fixed the vertical mounting faces of the angles and put a 2000 lb load on the bottom face of the tank. (I realize that I'm ignoring the bolted joints, and the pressure exerted by the oil on the tank itelf.)

But anyway, I ran the analysis, and it said that I have almost no stress even remotely near the angles. All of the stress is on the bottom of the tank. Which sort of makes sense because that's where the load is being applied. But there's almost no stress in the area of my reaction force. It's essentially a cantilever. I was expecting to at least get SOMETHING around my mounting brackets.

This is why I find the results a little suspect.  

Like I said, I'm no stress guy....but I'm not a COMPLETE moron....no matter what my wife may tell you.     

RE: So...how much do you guys trust Cosmos express?

send it to your VAR and see what they come up with

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP1.1 / PDMWorks 05
ctopher's home site

RE: So...how much do you guys trust Cosmos express?

(OP)
I don't have a VAR. We're 3 non-shop guys in the company

RE: So...how much do you guys trust Cosmos express?

I have not tried this, but maybe model it in sheetmetal and not extruding and see if there is a difference in CE?

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP1.1 / PDMWorks 05
ctopher's home site

RE: So...how much do you guys trust Cosmos express?

(OP)
wait a sec... it just dawned on me. Does VAR stand for  "<some V word> Authorized Re-seller"? I've been assuming that VAR meant some internal company IT guy...

sigh...I'm new...

RE: So...how much do you guys trust Cosmos express?

(OP)
Ooooohhhh..... Value-added reseller.... Ok...I guess I could contact them. I'll do that tomorrow...

RE: So...how much do you guys trust Cosmos express?

Value Added Reseller


Making the best use of this Forum.  FAQ559-716
How to get answers to your SW questions.  FAQ559-1091
Helpful SW websites every user should be aware of.  FAQ559-520

RE: So...how much do you guys trust Cosmos express?

COSMOSWorks Express is as accurate as anyother FEA program.  If you took the same arrangement of elements, properties, loads, and constraints developed in CWE and duplicated it in any other FEA program, you would get nearly identical results.

The problem is CWE's limitations on said elements, properties, loads, and constraints.

RE: So...how much do you guys trust Cosmos express?

I must say I like CosmosExpress. I'm a long user of ANSYS (and ABAQUS) and I use Solidworks to create inputs for them (primarly). It's a nice combination and very usefull. Now, when I saw for the first time CosmosExpress I said to may self, what is this litle joke around here? And I found that it does its job well if you know what to ask from it. If you're an unexperienced user, you'll obtain the same wrong answers no matter you use CosmosExpress or ANSYS as well. So, what is the domain of application of CosmosExpress:
-static analysis
-small deformations
-just one type of constraint: fully restraint
-no temperature time dependent materials (if I remember well)
-just for ELASTIC domain of deformations
-ONLY for ductile materials; the Von Mises equivalent stress apply just for this type
-no control of meshing process
-just force and pressure as input loads
In conclusion, can CosmosExpress be used for something? Remember that a lot of objects you design, fall in this category. If you need more detailed analysis you can take a step further and use CosmosWorks. If your object behaviour is more complicated (non-linear, dynamic,non-linear materials, creep, fatigue, etc), go with a good FEA program like ANSYS, ABAQUS, NASTRAN.
The tank drop analysis is a dynamic type one. Stresses can be in this case 5-10 times larger. The tank can undergo plastic deformations as well. Talk with a stress analyst to do your task (FYI,ANSYS has a drop module for this case).

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources