No, it is not like that. When using a tabular approach, you explicitly define the damage versus displacement relationship. This means that the stress-displacement response depends heavily on the provided tabular data. However, the damage initiation criteria (usually based on traction or displacement) still need to be specified and properly synchronized with the damage evolution data. If this isn’t done correctly, the stress response could become exaggerated or underestimated. On the contrary, In the bilinear form, the model defines a linear traction-separation behavior up to the damage initiation point, followed by a linear softening (damage evolution) based on the energy criterion. This method closely follows the theoretical stress-strain response in mode I fracture. This could explain why you're seeing twice the maximum stress. The model might be reaching a higher stress before the damage begins to evolve. Is it clear?

Dear @ Engr. Tufail

you said "the damage initiation criteria (usually based on traction or displacement) still need to be specified and properly synchronized with the damage evolution data" when we are using tabular approach for damage evaluation instead of energy criterion.

But the question is"how should we define damage initiation parameter?"

I realized that we should input max initiation stress value very little like 0.001 MPa instead of 21.6 MPa On the contrary when we entered in energy based approach.

If we do that we see that the S-U plot have the same Max stess value (21.6 Mpa) like energy based approach.

Am I rigth?