Stress-Strain graph 1

[Sweeney89]

Hi everyone,
I've performed an FEA on a model in Abaqus, for the same load area and boundary conditions, I have applied a Tensile and Compressive displacement, and my results show that The stress remains the same for each, and the strain is different. My question is, how would I best compare this data, As if I plot a stress-strain curve I can't have both curves on the same graph since the strain (X-axis) is different for each. A strain-stress graph is perfect, although would it be completely wrong in engineering terms? *I hope that makes sense*

I apologise if this is a silly question, but I've got a lot of assignments/projects on just now and my brain seems to be melting ever so slightly

Thank you!

 

[silvamat]

Hi sweeney,

You can still plot a stress-strain chart with different values on the x-axis. Just create a scatter chart, not the one with points, but the one with continuous line in MS excel.Just insert x and y values for compression and then x and y values for tensile and it should be fine. What is your geometry?? when you are modelling geometries with local weaknesses, different strain values may happen due to local instability phenomena, such as buckling. Don't rely too much on global maximum results, as it may not seem representative of the real mechanical behavior of the part. The justification of this are singularities that may occur. However, if you are applying a displacement distributed over a large area, this may not pose a problem.


regards,
Miguel Silva, MSc.

 

[Sweeney89]

Hi Miguel,

Thanks for taking the time to reply! It is actually two small lower jaws that I am modelling, one which is of a structure which would be expected to handle compressive loading effectively(wide, brash-looking jaw), and the other which would be expected to handle tensile loading effectively(narrow, elongated jaw). I am performing both compression and tensile tests on both. I.e. I will apply a tensile displacement then a compressive displacement on the exact same area (I am varying the size of the load areas). So for example, the jaw I expect to better deal with Tensile loading - I apply tensile and compressive displacement, the stress is the same for each, although the strain is less for the tensile displacement and higher for the compressive. There doesn't appear to be any sign of buckling on my graphs though, although now I understand that this should perhaps be the case as I increase the load area

Thanks again, it is much appreciated

Sweeney

 

[Sweeney89]

I have attached some graphs

 

[Sweeney89]

Sorry.... I attached some scatter graphs i have made up of the compressive and tensile stress strain graphs, the data has been taken from field output abaqus.rpt file, since my model has over 200,000 nodes and I am unable to plot the XY data in abaqus, so i have picked a selection of nodes from the text file! Could someone please advise me if I'm heading in the right direction?
The model I have used for the data above.. I would expect to deal with Compressive forces better than tensile!

Thanks so much, i do appreciate the help