Explicit Model won't work

[WillingToLearn]

Hello everyone,

I thought I had it figured out, but somehow my explicit model won't work. I have a very simple part (5x5):

with a relatively fine mesh (0.1):

Only Density, Elastic and Plastic properties were definded:

I somehow suspect, that the units are responsible. I use the following as my base units:
Length: µm
Mass: ng
Time: µs

Consequently, the other units that follow are:
Stress: MPa
Density: ng/µm³ (=kg/m³ divided by 1e06)

So the values that I have used:
Time: 1e06 (=1s)
Density: 0.00114 (=1140kg/m³)
Youngs Modulus: 1000 (=1GPa)

and the plastic values you can see above. I also attached the .inp file if anyone is interested.

The error message I get is: "THE ANALYSIS MAY NEED A LARGE NUMBER OF INCREMENTS (MORE THAN 20,000,000), AND IT MAY BE AFFECTED BY ROUND-OFF ERRORS. FOR ACCURACY, RUNNING DOUBLE PRECISION EXECUTABLE IS REQUIRED".

My research tells me, that this is caused by an error in the model. Since it is a very basic model I must have made a very basic mistake that I can't figure out.

Kind regards
Michael

 

[FEA way]

If you run it in double precision, it may work. But I would be extremely careful with those exotic units. Make sure that they are all consistent.

 

[WillingToLearn]

Thank you for the quick answer

The thing is: I have to use µm as I ultimately want to analyze a representative Volume element for a fiber composite. So basically only the length is set.

Which consequent units would you use in that case? I am a complete novice so picked them in a way that none of the consequent units are too extreme.

 

[FEA way]

I’ve never used such units but you have to pick base units first and then make sure that all the derived units are consistent with the base ones. In literature, you can find some examples of the usage of microscale units in Abaqus.