The prediction of risk of welding defects at the procedure stage using computer knowledge based systems.

摘要

The purpose of this research was to develop a methodology to evaluate thelikelihood of defective welds as a procedure proposal is entered into a computeriseddatabase system. The approach developed was assessed for hydrogen induced coldcracking (HICC) since this defect is a major problem in welding technology. Anexpert system was used to implement the methodology.The information for the expert system knowledge base was partly gatheredfrom previous work in this area. The technique necessary to analyze and incorporateknowledge was organized in a structured form including the major area to beattacked.The final system was implemented using an expert system shell. The globaltask of analyzing a welding procedure was broken-down into three different stages. Awelding procedure specification comprised the first stage. In the second stage, aninterface between the expert system software and a database was implemented.Having proved the feasibility and advantages of integrating the expert system shellwith a relational database the remainder of the work was devoted to the developmentof a strategy for operating the expert system and in particular dealing withuncertainty.Detailed validation of the knowledge base and the system as a whole wereconfined to a single defect type in the belief that the modularity of the system wouldallow extension to other defect types and the strategies developed in the present workshould it be applicable. Results have shown that the system performs well in thespecified area. Validation trials using simulated welding conditions generated by theexpert system have shown a very good correlation with practical results for differentclasses of steels. The integration between approved welding procedure records andprocedure qualification records could be the basis for a complete welding databasemanagement. Practical application of this system could be extended for educationalpurpose and training facilities.