Forming Behaviour of Micro-Structured Aluminium Sheets

For a deeper understanding of the forming behaviour of perforated aluminium sheets (Al99.5) in micro deep drawing processes, tensile and stretch forming tests are performed at forming speeds of 0.1 mm/s and 0.25 mm/s. The sheets have thicknesses of 100 µm and 200 µm, a perforated rectangular hole geometry of 300 µm x 300 µm and a bar width of 40 µm. During stretch-forming tests the flow characteristics and failure mechanisms within the mesh structure are determined. An isotropic forming behaviour with low ductility is observed. The maximum stretch-forming depth is increased at increasing perforated area. The mesh structure failure is peripherally obtained due to notch effects, friction and micro related size effects within the mesh structure. Moreover, the results show that cracks and necking within the mesh structure occur only tangentially to the punch movement due to high uniaxial stresses caused by the forming process.