Strain-Controlled Fatigue Properties of USS EX-TEN F50 Steel

A program was conducted to examine the variability of fatigue properties within a single grade of steel. Monotonic tension and strain-controlled fatigue tests were performed on longitudinal specimens from seven sheets of USS EX-TEN F50 steel obtained from five coils of three heats which ranged in thickness from 0.100 to 0.188 inch.

The results of this study showed that the slopes of the elastic strain, plastic strain, and stress versus reversals and stress versus plastic strain lines are not statistically different for the seven sheets. Also, the intercepts are the same. The results showed that EX-TEN F50 cyclically softens to strains of 0.5 percent.

This study gives no evidence that the strain-controlled fatigue properties of EXTEN F50 steel vary more among sheets from different coils than within a single sheet and, therefore, gives no evidence that sampling from more than a single sheet is necessary to estimate the fatigue properties.