Development of diagnostic expert system for environmentally assisted cracking(EXENAC) and importance evaluation of knowledge in inference.

Abstract

The expert system which diagnoses the sensitivity of environmentally assisted cracking (EXENAC ; EXpert system for ENvironmentally Assisted Cracking) has been developed using the OPS83 programming language. This system is composed of three independent systems, which respectively diagnose the sensitivity of I ) stress corrosion cracking of austenitic stainless steels in a low- or high-concentration chloride solution and/or high-temperature water, II) hydrogen embrittlement of high-strength steels in various aqueous solutions and gaseous environments, and III) hydrogen attack of steel in highly pressurized high-temperature hydrogen gases. The knowledge base consists of production rules, which have certainty factors to represent the uncertainty (contribution) of each rule to environmentally assisted cracking. Applying the developed expert system to the case histories the diagnoses were accurately made. We also proposed the quantitative measure to evaluate the importance of each rule in the diagnosis through the use of the developed expert system.