A CRACK GROWTH RATE MODEL COMPATIBLE WITH THE WOHLER FIELD

摘要

In this work, a dimensionally congruent model is developed to reproduce the complete crack growth rate curve. The model considers a normalized stress intensity factor range AK~(*+) defined in the domain [0, 1] that can be interpreted as a cumulative distribution function, thus taking advantage of the statistical experience inherent to this type of functions, in particular, in what concerns the parameter estimation methods. Beside this, a relevant theorem is then recalled showing the possibility of deriving crack growth curves a-N for different stress ranges △σ and initial crack lengths a_0 from a unique reference curve. In this way, the S-N curves can be derived from the crack growth rate curves as a function of the initial crack size proving the interrelation between the stress based model and that based on fracture mechanics. The model is applied to a set of experimental data from a certain steel alloy allowing us the derivation of crack growth rate curves and S-N curves for subsequent application in the practical assessment of the fatigue life of structures and mechanical elements.