A study on the failure of circular plates struck by masses. Part 1: experimental results

In the present study experimental results recorded from a series of tests are presented, which examine the dynamic response and petalling failure of thin circular plates struck transversely at the centre by masses having conical heads and spherical noses. The circular plates are cut from mild steel plates with five different thicknesses of 1.17, 1.5, 2, 3 and 4 mm and three different diameters of 250, 300 and 350 mm, to make a ratio of thickness to diameter ranging from 3.34×10⁻³ to 11.43×10⁻³. The impact velocity ranges from 3 to 11 m/s, corresponding to an impact energy varying from 100 to 1700 J. The radius of the sphere on the tip of conical head of the drop mass is chosen as 6, 8 and 10 mm. It has been observed that a necking circle is initiated approximately in the central part of plates along a small circle, which is directly under the transition circle from the spherical surface to conical surface of the drop mass. This is due to the excessive in-plane tensile strain. A through-thickness crack, then, is formed at one point on the circle, which is recognised as in-plane tearing failure. The crack is opened further and ends with a petalling pattern tearing failure around the crack for severe impact cases. It has been found that the critical impact energy required for the onset of failure varies significantly with the thickness of plates and the radius of spherical nose of the drop mass.