3-223. HARDNESS TESTING.
3-224. Hardness is the resistance of a metal to deformation by scratching penetration or indentation, and is usually a
good indication of strength. Metal hardness can be measured accurately by the Brinell, Rockwell or Vickers Process.
3-225. BRINELL HARDNESS. The Brinell technique is usually used to obtain the hardness of aluminum and aluminum
alloys. This hardness value is obtained by applying a load through a ball indenter and measuring the permanent
impression in the material. To obtain the hardness value of a material, divide the applied load in kilograms by the
spherical area of the impression in square millimeters. Hardness value of aluminum alloy is tested by applying a load of
500 kilograms to a ball ten millimeters in diameter for 30 seconds.
3-226. NON-DESTRUCTIVE TESTING/INSPECTION.
3-227. Aluminum and aluminum alloys are susceptible to stress risers resulting from notching, nicking or scratching. A
very close visual inspection is required of all raw material prior to any forming or machining operations. Before any
fabrication commences it is necessary that all scratches, nicks and notches be removed by sanding, polishing and filing.
3-228 thru 3-238. Deleted.