Learning Forum

[Yevhen Mishchuk]

Hello all. I need help. 

How to simulate in lsdyna the crushing of a material (rock) due to compressive stresses or of an impact using the SPH or MLPG method.

I tried to create a stone with SPH as a grid. As a material I set - elastic, or Coulomb-Mohr. And then I pressed with a rigid plate. But as a result the stone either does not receive any pressure at all, or the plate passes through the stone, or the stone is compressed but not crushed.

Can someone tell me where to find a guide on using the partial method in lsdyna (MLPG, SPG, SPH).  Or can someone tell me how to solve this problem.

[Ram Gopisetti]

Hi Yevhen Mishchuk, 

Please make sure that you model the contact between the stone( SPH) and the rigid plate (FEM) using the node_to_surface contact with reasonable SFM, SFS values and set the ITHK=1 in *CONTROL_SPH, The spacing needs to be (shell thickness/2) + particle spacing. Shell thickness is given in *SECTION_SHELL. 

MAT_173 offers damage and failure effects and make sure you use check EPDAM1 and EPDAM2. If you are unsure of these parameters use MAT_ADD_EROSION and set known failure criteria. 

Please perform a literature survey on the methods used by different authors and one stater study is given in the link  https://www.sciencedirect.com/science/article/pii/S1674775517302524

I recommend using the SPG /Peridynamics for these cases as they are more stable and better compared to SPH and may offer a better perspective to your study. 

You can learn more on the particle methods in the link https://www.lstc-cmmg.org/ex-advfem I am not sure of any premade guidelines on using these methods unless the authorised resources from Ansys learning hub. Try checking the public streaming platforms you might find some resources on how-to's on particle methods and some openly accessible documentation  on particle methods are in links

1) https://www.researchgate.net/profile/Riccardo-Andreotti-2/post/Can_you_provide_useful_information_on_Element-Free_Galerkin_on_LS-Dyna/attachment/59d63c15c49f478072ea7a42/AS%3A273747255201792%401442277839456/download/01_meshless_overview.pdf 

2)  https://www.dynalook.com/conferences/15th-international-ls-dyna-conference/spg/smoothed-particle-galerkin-method-with-a-momentum-consistent-smoothing-algorithm-for-coupled-thermal-structural-analysis

3) https://www.dynalook.com/conferences/16th-international-ls-dyna-conference/electromagnetics-spg/t10-2-e-spg-065.pdf

Currently, we do not support local-Petrov method in LSDYNA. 

Cheers, Ram