Patent ID: 8240209

Claim:
A non-destructive testing method for detecting a sign of failure that occurs when a high-pressure tank for storing a high-pressure fluid is filled with said fluid, said method comprising: detecting acoustic emissions generated by a deformation of a material, or by microcracks in a material, or a failure of a material in which said microcracks have grown, with an acoustic emission sensor; receiving a group of acoustic emission signals which are made up of elastic waves of the same frequency generated continuously for a short period; determining a hit rate in which said elastic waves are counted as one hit, said hit rate indicating a change in the hit over time; and measuring a pressure of the high-pressure tank and the acoustic emission signal while the high-pressure tank is filled with said fluid, wherein the sign of failure is detected by finding the change in the hit rate with respect to an internal pressure of the high-pressure tank corresponding to the hit rate, and the sign of failure is determined from a value at which the hit rate, which has been increasing in proportion to the pressure of the high-pressure tank when said pressure is less than the maximum usage pressure, does not increase further and reaches a saturation state.