Could you tell the error or warning messages? Or copy the solve file here...

that will help better to understand exact problem you are facing...

Mesh quality is important parameter in Non-linear analysis. See if you can improve mesh quality by any means, can try multi-zone meshing.

With contact elements, try analysis with bonded contact. It is a linear contact analysis. Sort out any convergence issues with this contact type initially. 

With frictional contact type, Augmented Lagrange formulation is preferred.

You can always add NR residuals and then run the simulation. If the simulation does not converge you can look into the residuals to see where the problem lies.

Also it will be helpful if you can explain what kind of errors and warnings you are getting.

I agree with them above. One thing I want to add is, did you try smaller initial time steps? 

Thank you for your replies. The problem I am facing is that the model can't converge.

Hey Gerges,

Yes but cause convergence problem will be understood if there is some warning or error in solve.out file.

Anyway, please find attached ansys document about obtaining convergence. Hope this helps you.

@Zheng Kang: I am using a step end time 0.02 s and an initial step of 5e-4 s. Do you think that I should decrease it more?

Yes, you should try smaller. I think you may set maximum time step to be 5e-4. Initial time step could be 1e-5. 

@Kang, thanks for your advice. It seems that it will take a very long time to get the model solved. The model has been runing for around 18 hours and it solved almost 13% only in +500 iterations.

I will let you know the results.

@Kang, I tried to set the initial time step to e-5 and it didn't work. I tried also e-6 too and I got the same result.

Any recommendations?

@Dipti M: The error messages are as follows:

"The solver engine was unable to converge on a solution for the nonlinear problem as constrained. Please see the Troubleshooting section of the Help System for more information.

The unconverged solution (identified as Substep 999999) is output for analysis debug purposes. Results at this time should not be used for any other purpose."

I am attaching a sample solver output file. Please let me know if you can help.

I have just reached an acceptable solution for my problem. In order to obtain convergence, using smaller minimum step time helps to solve such models but it becomes very expensive in terms of solution time. Using manual contact stiffness didn't help today get accurate and uniformly results, however using program controlled contact stiffness did. The latter option resulted in increasing the solution time too. Thanks for syour help. Wishing you all the best! 

Hi Gerges,

Sorry for late reply. Did not see site for days. But it seems the problem is with mesh. In your output file we can see following:

" One or more elements have become highly distorted.  Excessive          

 distortion of elements is usually a symptom indicating the need for    

 corrective action elsewhere.  Try ramping the load up instead of step  

 applying the load (KBC,1).  You may need to improve your mesh to       

 obtain elements with better aspect ratios.  Also consider the behavior 

 of materials, contact pairs, and/or constraint equations.  If this     

 message appears in the first iteration of first substep, be sure to    

 run shape checking of elements."

In non linear analysis, mesh plays an important role. Since you have already reached to a solution, I suggest try improving mesh once (of course in free time). Also check contact status for every body in your model.

Thanks for the explanation Dipti. I could solve the model by reducing the time step.

Much appreciated!

Adding substep and refining mesh are the conventional method,but huge amount of  computational time and hardware resource will be needed. any good ideas?

I am facing problems in solving a transient structural model. Any suggestions?

I have this error message:

the quality of mesh elements is not acceptable for the solution

Dear Gerges Youssef ,

I am also facing the same problem like you mentioned. I refined the mesh size upto 0.02 mm and step size ,

initial step size= 1000

minimum step size= 100

maximum step size = 50000

Can you please suggest me how did you fix this error.

Hossain did you solve it?

The followings are the most common solutions for convergence problems.

Reducing the step size, refining mesh, reducing discontinuity in the model specially at contact regions, increasing BCs such as displacment gradually and depending on the problem you can change convergence criteria in setting however you need to becarful since it can change the outcomes drastically.

If the results worked for you please recommend it.

I have a doubt regarding gravity problem. If we apply the gravity, for vertical body supported with wedge, then it shows body is falling down. Some nodes of vertical body shows distortion, though I used proper contact pairs and boundary conditions.

The main problem is how can I fix my vertical body so that while solution my body get lifted with the horizontal displacement of wedge???

Need help urgent