analysis of mechanical attachment on ansys

[pentek123456]

I am trying to do analysis of my mechanical attachments on ansys. When I upload the igs file of my mechanical attachment in ansys it loads up perfectly. But when I put 35 load steps from 1000lbf to 40000 lbf, The max. stress strain graph doesn't represent that of steel. By the way I am using structural steel just for the analysis purpose. Can anyone help me out as to how to properly do the analysis. Also the load steps applied are for buckling test. The way I did buckling is that I applied fixed support at the base and applied the force at the top.

[pentek123456]

I am trying to do analysis of my mechanical attachments on ansys. When I upload the igs file of my mechanical attachment in ansys it loads up perfectly. But when I put 35 load steps from 1000lbf to 40000 lbf, The max. stress strain graph doesn't represent that of steel. By the way I am using structural steel just for the analysis purpose. Can anyone help me out as to how to properly do the analysis. Also the load steps applied are for buckling test. The way I did buckling is that I applied fixed support at the base and applied the force at the top.

[The_Man]

Since you are importing the igs make sure that you have imported the body as a solid rather than a shell. When you import a default solidworks(may be it happens with other softwares too) igs of a solid CAD shows up as a shell(Only boundary) which is sometimes easy to miss as the imported body visually looks fine.

[pentek123456]

I made sure its a solid but it still gives me a problem. Am I doing the buckling test correctly. Also if I want to see where fracture occurs, is there a tool to diagnose fractures in ansys???

[Drew Price]

I was under the impression that fracture should occur where tensile stress is the highest..... http://fsae.com/groupee_common/emoticons/icon_confused.gif


Drew

[pentek123456]

i even tried tensile test. but i still don't get a similar stress strain curve. what happens is that after Ultimate tensile stress then strain decreases. I don't know why this is happening. After the U.T.S the strain should increase till failure but I can't seem to figure out the problem.

[Pico]

An analysis on a piece isn't going to give you a stress-strain curve. If you're doing a detailed analysis of a bolted joint you need to make sure your connections and constraints are correct. You should see from the deformation if something isn't correct. Any pictures of the sample?

[pentek123456]

My constraints seem correct. I'll upload a pic. I have so far been doing to analysis on static structural. Should i be doing it on linear buckling or transient structural???

[nowhere fast]

Have you changed the material properties to give a non linear stress strain curve (a piecemeal of multiple linear sections)?

Default ANSYS materials have a linear stress strain curve that continues to infinity.

[pentek123456]

yeah I did use non-linear material thats why I got a Ultimate strength but it looked too high and also after ultimate tensile strength, the strain decreases. it should increase until the material fails. but in my case its opposite. Also the connections that i are frictional connections and are: bolt to part 1, bolt to part2 and part 1 to part2. I will upload a pic shortly.