MIL-T-85048
4.3.7.1 Flattening of specimens. Specimens shall be flattened cold between parallel plates until the distance between the plates is not greater than four times the nominal wall thickness. When testing welded tubing, the specimens shall be so positioned than any detectable weld shall be in the area of smaller bend radii. When the tubing inner diameter is less than three times the wall thickness, the specimen shall be flattened until the flattened sides of the inside diameter are not less than 0.060 inch apart. Bend areas shall be examined visually for the presence of cracks or tears.
4.3.8 Sampling plan F for bending test. 0ne specimen of suitable length shall be selected from each lot.
4.3.8.1 Cold bend of specimen. The specimen shall be bent cold 180 degrees around a suitable mandrel of diameter equal to three times the outside diameter of the tubing.
4.3.9 Sampling plan G for Corrosion resistance (acidified copper-sulfate test). Two specimens shall be selected from each lot.
4.3.9.1 Preparation of specimen. Specimens of the as-received tubing (Full sections whenever possible) shall be treated for 48 hours in a boiling copper- sulfate, sulfuric acid solution of the following formula:
Copper sulfate (CuS04 . 5 H20), 10 gm. Sulfuric acid (H2S04 ) sp. gr. 1.84, 10 ml. Water (distilled), 90 ml.
The specimens shall be covered with a minimum of 30 milliliters (ml.) of this solution per square inch of specimen surface area. A reflux condenser, or similar device, shall be used to prevent change in concentration of the solution.
4.3.9.2 Examination. After exposure, full-section specimens shall be flattened between parallel plates by a gradually applied load normal to the axis of the tubing until the distance between the pressure plates is not greater than four times the wall thickness. Strip section specimens shall be bent cold 180 degrees around a suitable mandrel of diameter equal to 3 times the outside diameter of the tubing. In either flattening or bending, the fold shall be along a weld zone if the specimen is of welded tubing. The folded areas shall be examined at a magnification of 20 x to determine compliance with
3.3.2.
4.3.10 Sampling plan H for passivation. 0ne sample shall be selected to represent each lot of tubing.
4.3.10.1 Test for plan H. Tests shall be in compliance with method 102 or 103 of
MIL-STD-753.
4.3.11 Sampling plan J for hydrostatic pressure resistance. Two samples shall be selected to represent each lot.
4.3.11.1 Sample subject to internal hydrostatic pressure. Sample tubing shall be subjected to internal hydrostatic pressure calculated in accordance with 3.6. The pressure shall be applied at least two successive times for a minimum of 2 minutes duration each application. The rate of pressure rise shall not exceed 25000 psi per minute.
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