The simplest plasticity material model is the Bilinear-Kinematic. All you need to define is a Yield Strength. Use 0 for the Tangent Modulus. This will create an Elastic, Perfectly-Plastic material.
You should remesh the flat plate and put at least 4 elements through the thickness. If you make the elements Linear, you should put 8 elements through the thickness. This will help it stay bent.
You should use a 2D Plane Strain analysis to save on the solution time. You could also save some time by taking advantage of symmetry.
You don't need 21 steps, you can do it with 2 steps, but you will need to increase the number of substeps to 100 Initial, 100 Minimum and 1000 Maximum.
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