Learning Forum

[Chihi]

Hello Everyone,nIm running a Structural Analysis for a compressive Test on Bambo Ring. All I have is the Experiments Data which are the Displacement/Force for axial Compression Test and Strain/Stress Values for transversal Compression Test, knowing that the Tests were done on different Rings.nWhat I have to do is to compare the Numerical Material Properties extracted from ANSYS with the ones calculated from the Experiments Data for an isotropic then an orthotropic Model, decide which one will I use for further Analysis and finally adjust the Stress/Strain Curve obtained from the final Model till it gets the same Shape as the experimental Curve.nI started with the isotropic elastic Linear Model as it's the simpliest Model to use for stuctural Analysis then I have to run a Multilinar Hardening one. The Load is applied as a Displacement Value on 20 substeps and the Model is made from 2D Solid axisymetric Element. im using the Symmetrie tool to save me time and space as I am a student and have a limited Node number and I have to use Ansys CLASSIC.n1- Do you suggest me to input the Strain-Stress Data then plot the model behaviour in Postprocessing or to input just the Young's Modulus and Poisson's Ratio calculated from the Experiments?n2- In the first Case in 1- , how can I then adjust the Curve until it gets the same Shape as the experimental one?n3- Before I start with the Orthotropic Model I should model the tranversal Compression test, so I will get the tranversal Young's Modulus, Should I assume in this Analysis that the Model is isotropic?nI would appreciate any Help!nThank you!!nn

[Ashish Khemka]

Hi Array ,nnIf you already have experimental data available then why do a reverse analysis? YOu may refer to following post for discussion on plasticity:nn ,nnIf you already have experimental data available then why do a reverse analysis? YOu may refer to following post for discussion on plasticity:nnnRegards,nAshish Khemkan

[Chihi]

first thank you for your answer. nI already checked this post but i am not sure if i could change the final stress strain curve by changing the Young's Modulus after finishing the simulation.nI have 2 Data Tables, one for axial compression and one for transversal compression test from 5 series of the Experiment done on 5 different bamboo rings with +1000 values each. I don't really know how to input all of them in Ansys.nI have to Simulate the Experiments, get the stress strain curve , compare, then change the material properties until the experimental and the numerical curves have the same shape.nI have to compare the Material Properties gotten from the numerical Simulation with Ansys with the material properties calculated from the experimental Data. . My thesis is all about this Reverse Analysis actually.. so i'll be grateful if you could provide me more informations asap..n

[John Doyle]

I am not familiar with bamboo, but it is not a metal. Isn't bamboo more like a soft natural composite? Before you settle on a material model in ANSYS, you need to understand what criteria makes it nonlinear? Is it actually yielding or is in nonlinear elastic or both. I am not certain that it's behavior is consistent with the KINH or MISO material model in ANSYS. These material models assume yielding behavior consistent with typical ductile metals (i.e. distortion energy theory).

[Chihi]

you are right. Bamboo is not a metal and it has the same behaviour as Timber/wood. The nonlinearity is approved with the curves i got from the experimental Data and the research in the literature I made about this topic. So in the reality Bamboo is an anistropic, nonlinear and yielding material as it is from the Natural fibres and has no standard model in the FEA yet. that's why for the thesis i have to do what is called Idealization and start from the easiest and simpliest Model going to the more complex ones.nI attached the experimental curves from the axial compression test applied on 5 different bamboo rings. the first step which is to create a 2D and 3D isotropic linear model is finished. now I have to start with the Orthotropic and the nonlinearity behaviour. Ill be thankful if you can suggest me which steps i have to follow or maybe answer on my questions above.nnn

[John Doyle]

Perhaps a hyperelastic material model would be a better place to start as I do not see any linear elastic region in this data. It is nonlinear from the very beginning,nIf upon unloading, there is a permanent set, maybe a fiber reinforced composite with different plasticity material assigned to the fibers would be helpful.nI would also suggest exploring options available in ANSYS Composite Prep/Post for modeling a fiber reinforced composite. n