PSI - Issue 39

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Rosa De Finis et al. / Procedia Structural Integrity 39 (2022) 528–545 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 9. Paris’-like laws obtained by using TSA-based methods (double logarithmic scale).

6. Conclusions In this work, two Single Edge Notched Tension samples have been tested under fully reversed load to study fracture mechanics behaviour. The tests were assisted by optical microscope and an infrared camera, observing opposite sides of the sample faces. The optical microscope allowed the assessment of the crack tip position. Temperature scanning of samples surfaces allowed the assessment of thermoelastic data (amplitude and phase) and second-harmonic phase data, useful to evaluate both crack tip positions and stress intensity factor ranges. Δ T 1 , φ 1 and φ 2 maps were used to obtain SIF range and CGR in order to determine a Paris’-like law using different methods: • Based on direct interpolation method to obtain SIF range from Δ T 1 data ( Stanley-Chan’ method ) and CGR considering the φ 1 and φ 2 point inversions of profiles parallel to crack growth direction and related to the opposite dissipative behaviours in the crack region where plastic zone and crack-closure effect coexist. • Based on application of the over-deterministic system of equations obtained by combining the general expression of the thermoelastic signal and Westergaard’ – Williams’ solutions, to obtain crack-tips via a trial-and-error procedure and the parameters describing the stress state near the plastic region ( ΔK I , T s , A I3 ). The outcomes of the present work, are:  for SENT samples there is a good agreement in detecting crack tip using optical microscope and TSA-based methods;  As to Δ K I , the results showed that Stanley-Chan’ method, even though less robust than ODMs, provided Δ K I values more in agreement with FEM values;  ODM seems to systematically underestimate Δ K I according to these preliminary analyses. This effect could be due to crack closure effect. However, further analyses are required to investigate such a phenomenon.