A load history database system and an expert system prototype for the analysis of fatigue crack growth based on the concept of crack closure were developed on personal computer. A relational Database Management System software MS Visual Foxpro ver 3.0 was used for the load history database system and also utilized for the user interface of the expert system. Computing programs for the expert system were written in Borland C++.
In the load history database system, datacode and serial number are used to identify the history data. This system have 28 tables and totally 150 attributes(fields) to describe the load history data in detail.
The expert system prototype includes fatigue crack growth assessment module based on the concept of crack closure using da/dN-$ΔK_eff$ data as well as conventional crack growth assessment module using da/dN-$ΔK$ data. To assess fatigue crack growth life based on the concept of crack closure, da/dN-$ΔK_eff$ and $U-K_max$ data are required. The da/dN-$ΔK_eff$ and $U-K_max$ data obtained at Strength Design and Database Lab., KAIST, are available.
The expert system can perform fatigue crack growth analysis for a number of situations. 12 kinds of crack shape are considered including the actual crack shape in the geometry step and various random and programmed load histories are dealt with in the load history step. Even if a user does not have the sufficient data for the analysis, she or he is asked which data are availabe during the time of fatigue crack growth assessment. At the time, the proper routines are executed in accordance with the user*s answer. Therefore any engineering designer can perform fatigue crack growth analysis successfully by utilizing this expert system.