Agreed. How I read it 'deformation' is being used to describe an irreversible change to the metal foam's structure. This is akin to the flex-frames used in glas

Agreed. How I read it 'deformation' is being used to describe an irreversible change to the metal foam's structure. This is akin to the flex-frames used in glasses, they frequently lose their originally designed form (deforming), however they will retain it once the external force is removed. I believe they should be using 'permanent deformation' here to clarify the importance. Although I'm sure there's likely a better and more accurate term out there. It is confusing if you read 'deform' as you would for the result gained from poking styrofoam or bending a spoon.