NUMERICAL AND THEORETICAL MODELS TO PREDICT FATIGUE LIFE IN AGGRESSIVE ENVIRONMENTS FROM EXPERIMENTAL DATA

摘要

Corrosion fatigue produce sensible effects in the fracture mechanics of structural materials. Aggressive environments in presence of dynamic fatigue load are indeed responsible of multiple effects, regarding crack nucleation and propagation rates. Considering Ti-6AI-4V in air, inert paraffin oil and 3.5 wt.% NaCI mixture, environmental effects are sensible in terms of acceleration of Fatigue Crack Growth Rate - i.e. da/d/V vs. stress intensity factor AK. Several literature studies dealt with the topic in the past years. However, research has been focused mainly on the FCGR description, and the prediction of number of cycles to failure in aggressive environments is not addressed. In the presented poster, a methodology to obtain a numeric model which reconstruct da/d/V vs ΔK from experimental results, including crack length and applied stress, is presented and compared against literature data. Results are related to R = 0.1 axial test involving smooth and notched flat dogbone specimens, with varying notch radius. The proposed model is used to reconstruct the number of cycles to failure of the tested specimens, resulting in a satisfactory correlation with experimental data. Comparison with other literature models highlights the necessity to develop a proper numerical model with each test case.