PSI - Issue 68

Erik Calvo-García et al. / Procedia Structural Integrity 68 (2025) 809–814 Erik Calvo-García et al. / Structural Integrity Procedia 00 (2025) 000–000

811

3

Fig. 1. The main physical properties of these shots are summarized in Table 2. Almen intensities were obtained according to SAE J443 standard. The effectiveness of the shot peening treatments was evaluated with an optical profilometer Filmetrics Profilm3D.

Table 2. Properties of the shot media and Almen intensities of each treatment. Shot medium Size (mm) Hardness (HV)

Almen intensity (mm)

Silica microspheres Alumina particles

0.1 - 0.2 0.5 - 1.0

500 - 600

0.24 A 0.31 A

> 2000

a

b

Fig. 1. Shot media used in surface treatments: (a) silica microspheres and (b) alumina particles.

Fracture tests were carried out according to the ASTM E1820 standard using a servohydraulic dynamic test Walter Bai LFV-25 machine. The aluminium alloy specimens were tested in three surface conditions: (i) non-treated, (ii) shot peened with silica and (iii) shot peened with alumina. SE(B) specimens were machined according to the dimensions given in Fig. 2. The shot peening treatments were performed in both faces of the notch surroundings.

Fig. 2. Dimensions of SE(B) specimens used in the fracture tests.

In the precrack stage of the tests, specimens were subjected to load-controlled three-point bending cyclic loading with a frequency of 2 Hz and a stress ratio of R = 0.1. The crack lengths were measured using an Epsilon model 3541 extensometer by means of the compliance method. Crack growth rates da/dN were represented as a function of stress intensity ranges Δ K , and these curves were fitted to Paris law according to expression (1), where C and m are material constants. = (∆ ) ! (1)