A relational fatigue strength database system was developed on personal computer. The relational database management system FoxPro was used. The database system developed contains 3,018 S-N curves, 311 ε-N curves and 809 da/dN-ΔK curves. In addition, 280 fracture toughness data which are valid $K_JC$ data according to ASTM standard are contained.
Using extensive experimental strain-life curves data on 116 steels, 16 aluminium alloys and 6 titanium alloys, nearly all methods presently available for estimation of fatigue properties from simple tensile data are discussed in detail. That is, the Four-Point Correlation method, the Universal Slopes method, Mitchell's method, the modified Universal Slopes method, the Uniform Material Law by Seeger et al and the modified Four-Point Correlation method by Ong are evaluated in a quantitative manner by using new criteria proposed in this work, along with conventional error criterion. The modified Universal Slopes, Seeger's and Ong's methods, give good life and strain predictions for steels. Among them, the modified Universal Slopes method provides best results in life predictions and Seeger's method provides best results in strain predictions.
For aluminium alloys, new fatigue life prediction method from simple tensile data was proposed by optimizing the evaluation criteria. ADS Ver 2.01 was used for optimization.
A simple fatigue strength assessment system was developed. The system includes fatigue strength database and fatigue expert system for the prediction of crack initiation life of materials. The expert system is developed on the personal computer by using C language and an expert system developing tool, UNiK. With the fatigue strength assessment system developed, designers and especially, the beginner on fatigue strength assessment can easily estimate a fatigue strength.
