There are other methods to measure hydrogen embrittlement.

(2) Notched tensile test

This method is also called Stress Rupture Test or Sustained Load Test, used by US Air Force, Navy, Boeing, and Lockheed Martin, and is considered to be the most accurate means of testing. This is a delayed fracture test with a tensile testing machine where a notched test specimen made of high tensile strength steel is subjected to a static tensile load that is 75% of ultimate tensile strength. If the specimen does not fail within 200 hours of this static loading condition, it is considered to pass the test.
The test specimen is made of high tensile steel alloy (AISI 4340), annealed and machined, heat hardened, and ground finished. Lastly, a V-shaped notch with a v-valley radius of 0.01 inch is added to this test piece. The US military testing standards additionally calls for this test specimen to be cadmium plated after dry-blasting with 100~180 mesh aluminum oxide media. After an appropriate baking process, this test piece is subjected to a static tensile load 75% of the ultimate tensile strength and left alone. If there is hydrogen embrittlement present in the test piece, it will break at the notch in several ~ 100 hours.

(3) Douglas stress ring test

Also called "Stress ring test". this is a testing method provisioned in Douglas Aircraft company's overhaul manuals. This is a delayed fracture test where a prop-bar is inserted in a ring made of high tensile steel to obtain a static load 90% of the ultimate tensile strength. The test specimen is considered as passed the test if it does not break after 200 hours of this static loading condition.
A heat treated ring 60mm dia., 2.5mm thickness, 25mm width made of high tensile steel 4340 is used. Cadmium plating is applied and baked on this ring. The ring is then deformed into an oval shape in a vise for a prop-bar called Stress Bar to be inserted. The bar statically maintains the oval shape to create a stress equal to 90% of the material's ultimate tensile strength.

Reliability of this testing method is widely argued, and no other aero-space manufacturers or the US Air Force do not recognize this method, but since the method does not require any specialized test equipment, it is considered convenient.' C Ring is shown in Fig.1.