THRESHOLD VALUES STATISTICAL ANALYSIS IN 2091 Al-Li ALLOY FATIGUE CRACK PROPAGATION

摘要

ΔK_(th) is a key design parameter for the material behavior characterization. In this work a statistical analysis on ΔK_(th) experimental values was performed considering 14 fatigue threshold tests. Threshold values were obtained using the "load shedding" technique. ΔK standard deviation values and ΔK mean values obtained in Paris stage and in threshold stage were interpolated with a straight line. A new definition of ΔK_(th) based on the assumption of σ_(ΔK) value equal to zero were obtained. Scanning electron microscope fracture surface analysis allowed to identify the striation forming as a leading mechanism. Striation spacings mean values were correlated with the corresponding ΔK_(th) experimental values using a linear relationship.