I have a question about acquiring the softening part of the compressive stress-stain curve of concrete under uniaxial static loading. I have tried very different options: Concrete Damaged Plasticity model, different stress, strain, damage material parameters as input, Newton and Riks (arc length) calculation methods, but still have some problems getting the softening part of the curve.Has anyone have any suggestions to get a realistic softening in a static uni-axial test? Actually, the problem is always the same. The solution does not converge after the peak or sometimes before the peak.It gives the error message: Too many attempts made for this increment Have tried Newton and Riks methods. Have decreased the min time increment down to $10^{-25}$, decreasing it even further does not help either. I have tried both implicit and explicit calculations. I have seen numerous posts in the internet about not being able to get the strain softening part of the stress-strain curve of concrete but no answers on the solution. 
How to model softening of concrete?
matlab;finite element;python;nonlinear equations;computational physics