Crack Initiation and Extension under Penetration of Thin Metal Sheet

Quasi-static and dynamic penetration tests were conducted using thin metal sheets of extrasuper duralumin, corrosion-resistant aluminum alloy and cold-rolled carbon steel. The failure mode before crack initiation differed from that after the initiation. Therefore, formulae for estimating the energy-absorbing capacity were proposed for before and after crack initiation. Especially after crack initiation, we derived formulae of the relationship between energy-absorbing capacity by assuming that the shape of the petals was logarithmically spiral. By comparing the estimated values with the experimental ones, it was clarified that the proposed formulae were valid for the assessment of the energy- absorbing capacity of thin metal sheets under penetration.