(NOTE: A recommended polishing and etching procedure is to
grind or belt sand the tail cone assembly section and final
polish with papers 240, 320, and 400. Then etch with a reagent
of 5% nitric acid in ethanol or nitric acid in water, whichever
gives the best result with regard to distinguishing with the
brinell glass the demarcation between case and core). Observation
shall be made for compliance with the requirements specified.
4.4.6 Tensile test.-From each sample selected in accordance
with 126.96.36.199, two tension test specimens conforming to the tube
type specimen-1 prescribed by Method ASTM E8 of Federal Test
Methods Standard No. 151 (except that the B dimension shall be
1 1/2 inches long) shall be taken from the tubing, longitudinally
and 180 degrees apart. (Test specimens from welded tubes shall
be located approximately 90 degrees from the weld). Yield strength
shall be determined by either the offset method or the extension
under load method, as prescribed by Method ASTM E8. The limiting
set shall be 0.2% (0.002 Inches per inch of gage length). Equipment
used shall be in accordance with Federal Test Methods Standard No.
151, Method ASTM E8, and 4.3.4.
4.4.7 Hydrostatic test of body tubes.-All welded tubes
that are to be used for body tubes shall withstand the Internal
hydrostatic pressure as calculated by the following formula.
However, the pressure applied to the tube wall shall be 5,000
pounds per square inch (psi) if the formula parameters dictate
the use of pressure greater than this value.
Test pressure in psi
Min. specified yield point, psi
Specified min. wall thickness, in inches
Specified max. outside diameter of tube In inches
Any tube which does not sustain the hydrostatic test pressure
for a minimum of 10 seconds or evidences a permanent deformation
after hydrostatic test shall be rejected. Equipment used shall
be in accordance with 4.3.4.