please tell me in detail what the optimization graphs show? (see attached picture)
Which graph shows what?
What do the numbers on the vertical axis mean?
And what exactly does it mean when the graph proceeds horizontally over the design iterations?
The Objective Plot shows the value of the Objective Function (in your case this is the Compliance value for the structure) as a function of number of Optimization Design Cycles (or iterations) that were evaluated. The Maximum Critical Constraint Plot shows a Normalized value from 0 to 1 for the constraint that was most critical at each optimization design cycle. In your case, you only have one Design Constraint (DWEIGHT), so this plot shows the normalized design area weight (DWEIGHT) over each cycle. If you had more Design Constraints, the solution could have a different Critical design constraint from cycle to cycle. To show somrthing to the user, the graph only show the Most Critical one (whatever it is) at each cycle.