Perforation of Steel Plates at Various Temperatures

Abstract

The primary objective of this thesis was to investigate how the temperature affects the perforation resistance of the high-strength steel Armox 500T and the low-strength steel NVE 36. This was investigated both experimentally and numerically. Tensile tests were conducted at room temperature to obtain the material properties for both materials. The Armox 500T was shown to have a yield stress of about four times the yield stress of the NVE 36 steel, while for the ductility the opposite was true. The Modified Johnson-Cook constitutive relation and the Cockcroft-Latham fracture criterion were calibrated using the material data obtained from the tensile tests. By inverse modeling, the model constants were tuned until wanted material behaviour was obtained. Ballistic impact experiments were conducted at room temperature and at -40 ◦C. The target plates were subjected to impacts using 7.62 mm APM2 bullets. The objective was to determine the ballistic limit curve by curve fitting the Recht-Ipson model to the experimental data. Only a minor positive effect on the ballistic limit velocity was observed for the lowest temperature. The failure modes were shown to be more sensitive to different initial velocities than temperature inside the tested range. Numerical analyses were conducted using IMPETUS Afea Solver with the model constants obtained from the inverse modeling. The simulations gave good results for the ballistic limit velocity and they were able to capture the trends seen in the experiments with regards to failure modes. Ductile hole growth was shown to be the main failure mode for both materials at various temperatures. A sensitivity study was performed to see how sensitive the base models were to changes in different parameters.