Dear Houdini

Fracture thin solid object (thin box, in this case). The size of fractures are dramatically changes the look. Too small fractures result in soft metal...like Aluminum.
Set up soft constraints. The type is "Position".

Soft constraint gives us "force", "torque" and "distance" attributes. This time, I have been using "force" to reduce stiffness and increase it to twice than before.

08_metal_sheet