Hello Mhdi,

I think I already gave an answer to this question, but at the risk of repeating myself : you can use the option "CREEP STRAIN RATE CONTROL" option on a pressure load by modifying your input file. Given you have a target strain rate on a defined element set, the pressure will be calculated in order that the maximum strain rate on this element set is always between 0.7-0.8 and 1.5 times this target  strain rate.

Regards

Hi Etienne

I tried this option but the results are not reasonable. The problems that I had with this option were

1. When I just specify strain rate for this option I must change default values of the solution dependent amplitude and initial increment of the step and minimum increment size otherwise analysis will stop after 5 unsuccessful increment with too many attempt error. When I change these parameters, analysis progress for 11 increment and stops with the "system error code 529697949"

2. When I specify arbitrary values for equivalent creep strain in addition to the equivalent creep strain rate analysis completes but stress and strain values are not reasonable and I must give very long step time (5000 s) to see deformation in the sheet and stress and strain values that abaqus shows are very little and unreasonable. I requested "ER" in the field output request and magnitudes of this quantity differ with the magnitude that I specified in the inp file for strain rate (ER magnitudes are 0.0001 specified values).

There is an example in abaqus for superplastic forming that uses solution dependent amplitude but doesn't run and after 5 unsuccessful increments stops with "too many attempt error" and I don't know what's wrong with this example. If I could run this example maybe I could use solution dependent amplitude properly.

Because of the above problems that I faced I searched the web and found some articles and example in superplastic forming that needs strain rate dependent amplitudes. In this articles geometry was a circular sheet that under a controlled pressure becomes like a dome and author used well known relation sigma=pr/2*t and other relations to obtain a relation between pressure and strain rate. So I decide to find an analytical relation between pressure and strain rate but my geometry is a rectangular sheet and I don't know how to find a relation between pressure and strain rate.

In conclusion my problems are abaqus example, understanding solution dependent amplitude and strain rate control option and finding an analytical relation between pressure and strain rate.

In strain rate control command how to specify a proper creep strain data for my strain rate. Maybe the problem is I don't know how the creep strain changes during the analysis.

Thanks so much for the times that you spend to answer my question Etienne.

I found the problem with abaqus example

Abaqus examples are inp files and commands in these files are keywords. It is not possible to define all of these commands in abaqus cae and you must type some of them in inp file like *STRAIN RATE CONTROL option. When you import inp file in the abaqus you ignore these commands and so when you create a new job abaqus will create a new inp file based on the conditions that exist in abaqus modules so abaqus generates a new imperfect inp file and this job NEVER converge because of the incomplete input data.

So Always run abaqus example inp files in the job module.

I have problem with system error code 529697949. Did anyone face with this error massage in abaqus