Reasoning behind two Force/Displacement graph differences?

[OJM]

Hi all,

I am currently looking into the results of two models that I have created, they both have exactly the same geometry, loads, boundary conditions etc etc.

However one has elastic material properties and the other have elastic and plastic material properties provided.

I have plotted the Force-Displacement data for the two models and the results are shown in the excel sheet....

In the elastic model there seems to be a point in which as the force is increased, the displacement is not increasing... whereas for the elastic-plastic model it is to a certain degree linear, can someone explain this phenomena?

Also why is the force shown to increase greater than the 1000N force that I specified in the loading stage?

Many Thanks

Chris

 

[OJM]

the abaqus model

 

[Mustaine3]

You are using a Riks step, which means that the load is scaled with the load proportionality factor (LPF). Take a look at the manual to learn more about this. Is there a reason why you use the Riks step?

Your mesh consists of C3D8R elements with one element through thickness, which means you probably have hourglassing. Look at ALLAE in history output. I think your results are wrong/useless.

I would recommend you use C3D20R elements, a regular general static step and apply a displacement. With some minutes of partitioning you can also create a much better mesh.