Examination of Sample of 1 in. Armor Plate Showing Surface Defect known as 'Alligator Skin'

摘要

The purpose of this investigation was to make a microscopic examination of a sample of armor plate showing 'alligator skin' or 'surface veining', and to determine if these surface defects are cause for rejection. Ballistic tests on plate showing 'alligator skin' reported in Aberdeen Proving Ground Partial Report No. 190, indicate that portions of the plate where 'alligator skin' is more prominent have a lower ballistic limit than areas which are free from this defect. The material represented by the specimens studied in this report fails to meet the requirements under workmanship in the Specification AXS-54K (Rev. 4) Par. C-2a. Microscopic examination of the sample indicated that mill scale was rolled into V-shaped pockets and local decarbonization was present around the defects. These defects, together with segregations of nonmetallic inclusions near the surface, are sufficient to lower the ballistic limit as shown by the ballistic test.