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convergence problems

Convergence problems in Abaqus-Fortran

Hi mechanicians:

I decided to post because I have an inconvenience that is not shown in other posts.

I am working in the Abaqus - Fortran environment in a thermal analysis. After implementing a new procedure (which actually works), the .sta file shows me that it has problems in its unique step, more or less in the 60th iteration (it is supposed to get until 500). Twenty iterations after that gets into interruptions because the code cannot converge.

With these lines it is easier to understand my point:

ABAQUS - Does Newton's method affect the convergence rate of higher order incremental scheme such as RK4 implemented via UMAT?

Hello everyone,

I'm currently doing an analysis on the convergence rate of an incremental model that I have implemented in ABAQUS using a UMAT. Here's the BIG lines of the problem:

1) In UMAT : Solution of a differential equation using explicit Runge-Kutta 4 (RK4), which has a 4th order convergence rate, yields the stress state "S". (In my problem, stresses are applied)

shabber hussain's picture

non linear analysis of a cylinder


I am working on post buckling of a cylinder in ANSYS. I have included imperfections using NLGEOM command. I applied a load which is slightly higher than eigen value buckling analysis and i am using displacement controlled analysis using arc length method. I am getting the following error after certain time

"solution not converged

Arc length  value has reached its minimum allowed value

Run terminated"

Can anyone please help me how to resolve this issue.....

Structures in fire


Are there researchers working on specific areas in offshore structures? Or is anyone covering the material behaviour of structures at elevated temperatures? I am indeed challenged to read about excitng contributions from different scholars expecially in structural mechanics. I realise I have just begun a race in research. You could help me gain the proper direction in research.

I shall be glad to get any response. 


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