three point bending experimental data vs simulation

[Aminpd]

Hello everyone,

I am working on a simulation of three point bending using ABAQUS. I used Johnson-Cook hardening model. In the experiment i rectangular steel bar was bent and afterwards unbent and the Force-Displacement(F-D) data was extracted. There were no strain gauges on the specimens therefore the strains should be calculated analytically. The goal is to compare the experimental data with the simulation to modify the hardening model.
I am interested in the converting the Force-Displacement(F-D) curve into Stress-Strain(S-S) curves in Three-Point-Bending tests. My problem is that the Stress equations mentioned in Some papers (one is attached in this Post) do not work in the plastic regime but somehow the S-S curves were calculated and it looks like that they are simply are a scaled form of F-D curves. The other problem is to calculate the residual stress for the unbending part, which I could not find useful resources to deal with it.
I am looking forward to hearing from you.

Best regards

 

[rb1957]

next time you post a large document, you may help us to help you by saying graph X on page Y.

You appear to be yielding the material, but did they do that in your reference ? TLDR.

I would consider photo-elasticity for what you're doing ... evaluating the stress state under different loadings.
I guess you're seeing the folly of not measuring stress in the experiment, but even measuring the stress locally would only give very limited data.

Is this school (or thesis) work ?
If for work, then you'll need to give us a tonne more information about what you're doing, and whether you've tracked down the original papers (on the Johnson-Cook hardening model). material, initial plastic deformation, residual permanent deformation, reverse loading.
You're using ABAQUS, you should be able to tune the model to give you the force-displacement curve from the experiement, and then that'll give you the stresses.
Or are you asking for a hand calc procedure to check the FEA ?

another day in paradise, or is paradise one day closer ?

 

[Aminpd]

Hello rb1957,

thanks for your quick response. I will surely do that(for the graph address). I meant figures 19 and 20 on pages 29 and 30 of the document. BTW on the page 30 there is a formula to calculate stress which I think can not be used in the plastic region. (maybe?!)
No, in this paper they tested composite material. I uploaded it only to show the point that:
"the S-S curves were calculated and it looks like that they are simply are a scaled form of F-D curves."
yes I am a student and it is a thesis work. I am also reading the original papers but for the residual stress I can not find the useful papers which can help me with calculations.

""Exactly! I am asking for a hand calc procedure to check the FEA.""

Thanks again.

 

[TiCl4]

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