PSI - Issue 53

America Califano et al. / Procedia Structural Integrity 53 (2024) 185–189 Author name / Structural Integrity Procedia 00 (2019) 000–000

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characterized by a notch directed along the rolling direction and are indicated as LT1, LT2, etc. In this contribution, the results for the specimens TL1, TL2, LT1 and LT2 are shown.

Fig. 1. Schematic of the 17-4 PH rolled plate with main dimensions (in mm).

A total of six specimens was tested: two obtained from the AM material and four obtained from the wrought material. Each specimen was equipped with a CEA 06-032UW-120 Back-Face Strain-gauge (BFS) and four of them, two for each material, with a Crack-gauge (CG) as well, which was characterized by 20 filaments and by a distance of 0.254 mm between two adjacent filaments. The specimens were subjected to fatigue tension-tension tests, according to the ASTM647 standard, by means of an Instron 8502 testing machine, having a load cell of 20 kN. The applied fatigue load was characterized by Pmax = 4500 N and R = 0.1. The specimens before the tests were pre cracked with a 1.3 mm-long crack. Data collected through the BFS and the CG were compared and calibrated by means of the BFS compliance method proposed in literature (Newman et al., (2011)) for monitoring the crack-length-against-cycles valid for the standard C(T) and for a wide range in crack-length-to-width ratios. The Newman-Johnston equations can be calibrated using the data coming from the BFS and the data coming from the CG, in order to find the material’s Young modulus E . 3. Results and discussion As anticipated in the previous Sections, the selected C(T) specimens were subjected to fatigue tests which ended as soon as each specimen reached the total failure. The data collected through the BFS and the CG were used to calibrate the Newman-Johnston equations so to find the Young’s modulus for both the AM and the wrought material. It was found out that the AM material had E = 165 GPa (Califano et al., (2023)), whereas for the wrought material E was equal to 195 GPa. The crack-length vs. number of cycles curves for the specimens LT1 and TL1