AE01.pdf

After interpretation acceptance criteria are applied

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After interpretation, acceptance criteria are applied in a phase called evaluation . Reliability of Test Results When a test is performed, there are four possible outcomes: (1) a rejectable discontinuity can be found when one is present, (2) a rejectable discontinuity can be missed even when one is present, (3) a rejectable discontinuity can be indicated when none is present and (4) no rejectable discontinuity is found when none is present. A reliable testing process and a qualified inspector should find all discontinuities of concern with no discontinuities missed (no errors as in case 2 above) and no false calls (case 3 above). To approach this goal, the probability of finding a rejectable discontinuity must be high and the inspector must be both proficient in the testing process and motivated to perform with maximum efficiency. An ineffective inspector may accept parts that contain discontinuities, with the result of possible inservice part failure. The same inspector may reject parts that do not contain rejectable discontinuities, with the result of unnecessary scrap and repair. Neither scenario is desirable. Acoustic Emission Test Standards Traditionally, the purpose of specifications and standards has been to define the requirements that goods or services must meet. As such, they are intended to be incorporated into contracts so that both the buyer and provider have a well defined description of what one will receive and the other will provide. Standards have undergone a process of peer review in industry and can be invoked with the force of law by contract or by government regulation. In contrast, a specification represents an employer’s instructions to employees and is specific to a contract or work place. Many a specification originates as a detailed description either as part of a purchaser’s requirements or as part of a vendor’s offer. Specifications may be incorporated into standards through the normal review process. Standards and specifications exist in three basic areas: equipment, processes and personnel. 1. Standards for acoustic emission equipment include criteria that address transducers and other parts of a system. 2. ASTM International and other organizations publish standards for test techniques. Some other standards are for quality assurance procedures and are not specific to a test method or even to testing in general. Tables 3 and 4 list some standards used in acoustic emission testing. The United States Department of Defense has replaced most military specifications and standards with industry consensus specifications and standards. A source for nondestructive test standards is the Annual Book of ASTM Standards. 5 3. Qualification and certification of testing personnel are discussed below with specific reference to recommendations of ASNT Recommended Practice No. SNT-TC-1A. 6 Personnel Qualification and Certification One of the most critical aspects of the test process is the qualification of testing personnel. Nondestructive testing is sometimes referred to as a special process.
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  • Fall '19
  • Nondestructive testing, Acoustic Emission

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