RUPTURE OF THIN DUCTILE TUBES BY OBLIQUE IMPACT OF FLAT-NOSED MISSILES - ANALYSIS

A theoretical model for deformation of a thin ductile tube hit at a la rge angle of obliquity (30 degrees < phi(0) less than or equal to 60 d egrees) by a rigid flat-nosed missile has been developed in order to p redict the impact speed for rupture. This analysis is intended to depi ct the principal phenomena that occur during the rupture process of th e tube. The contact force between the missile and the tube during pene tration is determined from an analysis of the local deformation. The m issile motion and the global deformation of the tube are calculated on the basis of rigid-body dynamics and a beam-on-foundation analogue. W hen the missile penetrates the tube wall by a critical depth, delta, the contact force is large enough to cause plastic flow through the tu be wall thickness. Tensile strain epsilon begins to develop beneath th e crater. Rupture is assumed to occur in the tension region when tensi le strain in this region reaches a value equal to the true strain at f racture of the tube material. At impact speeds below the impact speed for rupture, the missile does not perforate the tube wall but ricochet s from the tube. Calculations of the impact speed for rupture of a thi n tube hit at a large angle of obliquity by a flat-nosed missile are c ompared with experimental results for mild steel tubes. The effect of the ratios of missile diameter to tube thickness D-m/h and missile len gth to diameter L/D-m on the impact speed for rupture of thin ductile tubes are examined. (C) 1998 Elsevier Science Ltd. All rights reserved .