Sampat Kumar
Ansys Employee

Hi Sachin, 
In real life, the material follows the non-linear curve but for the linear analysis, the software follows the same linear path after crossing the yield point. In the linear analysis, the failure is concluded by comparing the maximum stress value with the yield or ultimate value. 

For the linear analysis, you have defined the material property for the elastic region only. Since you applied the load of 1800N and the stress exceeds the defined elastic limit of the material then failure would occur in the model. you have to perform the Non-linear analysis for this. 

For Non-linear analysis, Since your model is not converging then you can check the following points that might be the reason for this strange behavior.
1. Increase the sub-steps in the analysis setting. 
2. Verify whether the stress developed in the model is localized. there might be a chance of stress singularity in the model. I would suggest you to check how much area is showing stress more than the yielding. 
3. Will you please check that the model you are using for the simulation is the same as your experimental specimen? If the model is different then the maximum stress contour developed in the model is distributed over the area or not as per your expectation. 
4. Please verify that the large deformation is on or off for the non-linear analysis. 

Since the result is not fully converged, taking the midpoint result depends on your expectations and the analysis you are performing.