Mechanics for dent/deformation removal Henry Tan Tuesday, 10/2/09

Elastic / Plastic Behaviours Some material property, such as macroscopic yielding stress microstructures such (grains, dislocations) are unrecoverable Geometry: recoverable → dent/deformation removal dent Recovering dents and deformation of sizes of 25 mm – 100 mm in width and mm in depth.

Plasticity Uniaxial loading Multi-axial loading Plasticity teaching note: von-Mises yield criterion:

Vacuum pressure to lift the dent to it's normal position Pulling

Pulling of a Circular Plate R: radius of the pressurized area h: thickness ~ 1-2mm R pressure p

Critical Pulling Pressure r: radius for the occurrence of plasticity deformation r R pressure p Material regarded as rigid/perfect plastic: Reference: Applied Plasticity, by Jagabandhu Chakrabarty R r

Dent at the Edge?

Tension Tensile traction: locally flatten the surface Using dry ice to contract the dent, causing it to pop back into original place It may work on steel panels but not aluminum, and also depend on the thickness.

Plastic Bucking of Thin-Walled Structure Analytical solution?