Abaqus explicit displacement error

[alima2065]

Hi everybody,
I am modeling a coupon test in which the end of the specimen is pulled to a certain displacement. I am using the explicit solver and I used amplitude to define the displacement. But when I did the analyses the output showed that the specimen wasn't pulled to exactly the final displacement that I specified. for example I defined the final displacement as 5.16mm but Abaqus applied only 5.142mm. I even used the time points to write the output at exact time points and also added some additional time with fixed displacement at the end of the amplitude. But they did not work. I appreciate it if you could help me to find the source of this error and how can I handle it?

My amplitude
0 0
0.1 0.1
0.2 0.2
0.3 0.3
0.4 0.4
0.5 0.5
0.6 0.6
0.7 0.7
0.8 0.8
0.9 0.9
1 1
1.2 1

 

[FEA way]

How do you measure this displacement in odb ? The difference is rather small, it might be some numerical error.

 

[IceBreakerSours]

Are you getting your output from the node on which the displacement BC was applied?

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[alima2065]

Thanks for the reply. I used the XY plot for the point that displacement was applied. My confusion is that the displacement is not the response of the model. Actually, it is the boundary condition (input). I am not sure, but such numerical errors should be involved in outputs, not inputs. what do you think?

 

[alima2065]

Yes, it is a reference point that was coupled to the end nodes of the specimens by kinematic coupling.

 

[alima2065]

I found the reason for the error. It was about precision. When I used double precision the displacement was exactly as the input.

 

[IceBreakerSours]

Good catch. If you expect "lots" of time steps in your analysis, then significant differences are expected to show up if you use a single precision binary, which is why a double precision binary is recommended.

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