Choose Home tab→Modify group→Delete list→Delete Relief Faces 
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By default, all system-generated interior rounds and bend relief are selected. You can use the Select Zero-Radius Faces and Select Bend Relief Faces buttons to change the selection.
On the command bar, click the Preview button.
On the command bar, click the Finish button.
Tip:
The faces you delete in the Simplify Model environment are added to the Simplify section on the PathFinder tab.
You can use the commands on the shortcut menu to edit, suppress, and rename the simplified features you define.