ADHESIVE BONDING: ANSYS HELP NEEDED 3

[phantom12]

Hi

I am trying to model a single lap joint in ANSYS workbench (APDL not available for college). i build three solids ( 2 adherends and 1 adhesive), input the adhesive properties, meshed using contact size meshing. I also put pressure of 1000 psi on one end and fixed support on the other. I did it using static structural. However, i cannot get a solution, its says general solver error. Did i miss something?? Thanks

 

[rb1957]

1) student posts ("not available for college") are not allowed

2) there's an ANSYS forum that'll be more helpfull, but see 1)

 

[phantom12]

Sorry my bad. How do i delete this thread?

 

[blakmax]

Phantom 12

Modelling adhesive bonds using FEA is tenuous at best. I am not an FEA person but I believe that the biggest problem is the aspect ratio for the elements. In Australia, The Defence Science and Technology Organisation developed their own special adhesive elements to enable a sensible analysis.

Even if you do get a model to work, the problems are not over. Almost certainly your analysis would be a linear elastic model and adhesives do not behave that way. They are elastic-elastoplastic and unless you model them at least as elastic-plastic your solution will bear little resemblance to reality. You need a plastic analysis.

Next is the issue of adhesive design data. Most available data is generated using an average shear stress approach which is meaningless. (If you double the bond area you do not halve the maximum stress.) The design data should be elastic-plastic as generated by a thick adherend test.

There is some (non FEA) information on the correct methodology for joint design at DOT/FAA/AR – TN06/57, May 2007. You can get a copy if you google Adhesion Associates follow the links to the papers and look at paper 54.

Regards

Blakmax

 

[jedward]

Look at the work on fea for adhesives done by Alson Hathaway and some material presented in Paul Yoder's book on mounting optics.
They show how the effective modulus changes with aspect ratio for the adhesive. See also works by Victor Genberg and the SPIE short course notes.
Hope these are helpful.