Crack propagation model

[sithlord382]

Ive created a 3d cube model in abaqus and incorporated a 3d shell extrusion that is supposed to represent a crack in the cube model. I have assigned loads to the faces of the shelled 'crack' part to simulate tension, as i think that will open the crack. This was done by creating 2 surfaces, one for the top of the shell surface and one for the bottom surface. The said loads were then applied to the two surfaces. When i run the model the following error message comes up and the job is aborting. Does anyone have an idea where im going wrong?

Error in job Job-1: SURFACE DEFINITION ASSEMBLY_SURF-1 NOT FOUND.
Error in job Job-1: SURFACE DEFINITION ASSEMBLY_SURF-2 NOT FOUND.
Error in job Job-1: THE SURFACE ASSEMBLY_SURF-1 HAS NOT BEEN LOCATED
Error in job Job-1: THE SURFACE ASSEMBLY_SURF-2 HAS NOT BEEN LOCATED



Thanks in advance

 

[tkks2040]

Are you using XFEM crack propagation? If yes, the shell instance is suppressed after you define the initial crack using the shell. The surfaces would then be invalid for load definitions.

 

[sithlord382]

yeah im using XFEM modelling, so does that mean i cant apply loads onto the surface of the crack? When you say shell instance is suppressed, when i defined the crack in (interactions) the 'non crack' cube was suppressed and then resumed once the crack location had been assigned. I suppressed the crack shell but resumed it once i had created a new set for the cube domain. Do you have any idea how i can go around this problem, as i want to simulate the crack opening and propagating when under tension
Thanks in advance

 

[tkks2040]

I don't think you can apply loads on the crack surfaces through this approach. You can apply loads on the top and bottom surfaces of the cube.

 

[sithlord382]

ok thank you for your rapid reply and help. I also found out that when i apply tensile loads to the surfaces of the cube, a crack will only form in the length of the shell that i created for the crack i.e. if the crack shell has a length of 2 the crack will only open at a length of 2. If the length is 5 then the crack will only open until a length of 5. Do have any idea what i have to do to show what happens after. I want to simulate the cube being under enough tension force that the crack opens, propagates and causes the cube to shear into 2.

Thanks in advance

 

[tkks2040]

Hello sithlord382. You will have to specify damage criteria for the material. Goto Material>Mechanical>Damage for traction separation laws>Maxps damage. Or similar damage criteria.

 

[sithlord382]

This may sound like a stupid question but where can i find these values for materials such as concrete or steel? Ive searched the net but havent gotten far.

Again thank you for your help!

 

[tkks2040]

Please try googling with keywords pertaining to the type of problem you are solving. Eg. Steel crack propagation abaqus damage criteria.

 

[sithlord382]

Ive tried for concrete but i cant find any reliable values for max principal stress and i dont know what to enter for damage evolution? Do you hvae any suggestions?

 

[sithlord382]

Hey tkks2040,

would you by any chance know how to assign boundary conditions on my said cube if i wanted to simulate the 3 different modes of fracturing?