Reply To: Difference between SPG IDAM=1 and MAT_ADD_DAMAGE

[Oleg Makarov]

Sorry, but I don't understand you at all. In this post, I am asking about MAT_ADD_EROSION, but not about MAT_ADD_DAMAGE or any damage at all.

"IDAM controls the mechanism of damage where as MAT_ADD_DAMAGE controls the criteria for the material" - as I understand IDAM controls failure criteria too by parameters FS and STRETCH. Different IDAM values control the failure quantity that will be assessed (plastic strain (IDAM=1), shear strain (IDAM=3), etc). Therefore I don't need MAT_ADD_EROSION or another cards to simulate material failure for the case MAT_24 + IDAM=1.

"for MAT_24 with IDAM 1 has to be used and it is coherent to plastic strain defined in that material card and you dont need to define the FS vale again in the section cards" - why?? In MAT_024 we define only the yield stress vs. plastic strain (hardening rule) and therefore we have to set the failure criterion inside SECTION_SOLID_SPG, right? I use ANSYS 2023R1 (LS-Dyna R13.1), maybe it is important...

"Moreover, MAT_24 is not good for brittle materials" - this is my main question - why I can not model brittle material if I set very very small value of critical plastic strain (parameter FS)? Since this value is very small the fracture should be the same as if I define the critical stress in MAT_ADD_EROSION.

BUT when I tried this I found that material crushing looks very different for these two options. I am wondering because SPG bond breakage follows the same rule - FS > FS_critical & STRETCH > STRETCH_critical.