Yade

hollow glass sphere modeling using pfacet as a filler in cement paste

Asked by hanzj

Dear all,
I am new in YADE， I have installed YADE from source code and learned the basic knowledge about YADE. After reading the paper of prof.Bruno Chareyre, named ''Modelling of deformable structures in the general framework of the discrete element method'', the job of Bruno's motivates me a lot. I am now doing the simulation as follows :
Hollow glass sphere, whose d(0.5) is about 40μm， acts as a filler in the cement paste.the cement's d(0.5) is about 20μm.The fresh cement paste is made up of cement and water, and the ratio of water to cement is ranging from certain values, for example,0.3,0.4,0.5. after the cement paste formed, the hollow glass spheres are mixed into the paste. After the cement paste hardened， there exist bonds between the cement paste and the hollow glass sphere.
I was thinking about regard it as a two-phase system, so the interfacial properties between hollow glass spheres and cement paste would play a key role. and I was going to use a REV （a cube whose size supposes to be 100μm），which first contains one hollow glass sphere, whose radii suppose to be 40μm and cement paste around it. any ideas about how to decide the size of the REV cube? and then， the cube would be uniaxial compressed.
So,question 1: I was wondering if I can use the pfacet to modelling the hollow glass sphere, whose properties are more similar with a hollow deformable shell but can break down in a brittle mode. To model its failure mode, which material do you recommend? whether the cohesive friction mat or cpm mat? can i use them?
question 2 : the cement paste i was thinking about modelling it using spheres and cohesive-friction mat. can I? and there exists a bond between the glass sphere and the cement paste. so if i can use the pfacet to model the glass sphere,I have to use the sphere-pfacet geometry like Ig2_Sphere_PFacet_ScGridCoGeom(),right?
question 3: whether i can use 'matchMaker' to define the specific cohesive force or something else determine the interfacial properties between the pfacet and the spheres? i would appreciate it that if you can recommend me something to learn about this.
Looking forwards to your advise and thanks a lot.

best regards
hanzj

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Bruno Chareyre (bruno-chareyre) said : 		#1

Hello,
Q1. Maybe but it will need exploratory steps to discover if it can work. PFacet splitting has not been in our line of thinking until now so it is difficult to anticipate all the possible problems. One problem will be the creation of volume when one cylindrical element will become two (because two facets are detaching).

Q2. Yes, it makes sense.

Q3. I would say you can do what you want to do without MatchMakers but maybe I miss one part. Anyway, the simple method will work at least for simple experiments: loop on the interactions and assign the adhesion to the different groups of contacts as you like it.

Bruno

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hanzj (hanzj14) said : 		#2

dear prof.Bruno:
Thank you for your reply, and I understand what you mean mostly.sorry, I still need your help as follows:
first,I have searched for what you recommend "assign the adhesion to the different group", for example ,the question "https://answers.launchpad.net/yade/+question/257929"[1] .is that what you meant? and I would try to use it then and put my simple scripts here.
another question, if i am going to model the nano indentation process, and i would like to use PFacet to model the hollow glass sphere, just not take into account the splitting of the PFacet, it remains elastic or even plastic state. and i use a spherical indenter to indent the composite made of glass sphere and cement paste. I want to use DEM to model the nano indentation because my material tends to be a particular problem, and I am going to model the loading and unloading process and plot the diagram between the repulse force acting on the spherical intender and the indenter displacement. there are other authors use FEM to model the indentation like http://www.sciencedirect.com/science/article/pii/S0040609016302966[2], are there any other authors using DEM method or even YADE to do that? how to calculate the repulse force acting on the indenter? The bonds between the sphere and cement paste might be week enough to break down first and i have to calibrate the adhesion between two different materials, right? any ideas or recommendations?
If I have any logical problem and state that not correct, could you please let me know, thank you.

looking forwards to your reply.

best regards
hanzj

"https://answers.launchpad.net/yade/+question/257929"[1]
http://www.sciencedirect.com/science/article/pii/S0040609016302966[2]

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Bruno Chareyre (bruno-chareyre) said : 		#3

Hi,
[1] is along the line I was mentioning, yes.
Getting the total force on the indenter will just need to sum the forces on every elements of the pfacet surface.
I have no experience in this sort of problems so I'm not the person to advise much more.
Something I am wondering now is if the filler could not be simply a big sphere. Do you really need a hollow sphere?
Bruno

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