using mat_184 as simple springs by making up numbers

- July 10, 2025 at 2:55 pm
  
  Dennis Chen
  Subscriber
  
  I would like to ask the community or Ansys employees if it's a reasonable approach to use mat_184 as just springs with some stiffness I arbitrarily define and a failure traction value that I made up as well basd on the cohesive element size I am using.
  Basically, is there any meaningful way to actually calibrate a CZM model like mat_184 or was this mat card created just as a very rough simplification. It would be good to understand why this card was created originally for what purposes.
- July 14, 2025 at 1:58 pm
  
  Ram Gopisetti
  Ansys Employee
  
  Hi Dennis,
  MAT_184 serves as the foundational cohesive model available in LS-DYNA, specifically designed for applications within the intact region of the bilinear cohesive law. To calibrate this model, peel tests must be conducted under different loading modes—Mode 1 (normal pull) and Mode 2 (shear pull). The stiffness values $K_n$ and $K_t$ are then computed as the ratio of maximum strength in Modes 1 and 2 to the corresponding traction values in each mode. These computed values should be entered in the KN and KT fields.
  If failure modeling is required, the displacement at which a cohesive element fully fails should be specified in the FN_FAIL and FT_FAIL fields, corresponding to Modes 1 and 2, respectively.
  While MAT_184 is effective for basic cohesive zone modeling, LS-DYNA also offers more advanced material models such as MAT_138 and MAT_240, which provide enhanced capabilities including rate dependence, complex cohesive zone modeling laws, and more detailed failure criteria.
  Please do more literature review on this topic, as it may get close to helping you with the calibration of this model.
  Cheers, Ram