PSI - Issue 71

Oleg Plekhov et al. / Procedia Structural Integrity 71 (2025) 10–17

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The residual stress profiles in the depth of the specimen, obtained through the numerical modeling, are compared with the results of the experimental measurements of the residual stress magnitude by drilling holes according to the standard of the American Society for Testing Materials (ASTM E837-13a). The numerical distribution of the residual stresses at the surface of the specimen after one pass and after two passes is shown in Fig. 7.

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Fig. 7: Residual stress after LSP: (a) σ x after one pass, (b) σ y after one pass, (c) σ x after two passes, (d) σ y after two passes 6. LSP effect on fatigue life of titanium specimen with stress concentration To illustrate the LSP effect on fatigue properties, we have treated Ti-6Al-4V specimens presented in Fig. 1 (b). The treatment is carried out with a square profile of 1x1 mm in size, the pulse duration was 10 ns. Fig. 7 shows the geometry of the treated areas. The processing is carried out with a power density 20-30 GW/cm 2 . The laser spot shape was square, with side lengths varying from 1 to 3 mm. A circular laser spot with a diameter of 2 mm was also used. The spot dimensions and overlap lengths are presented in Fig. 9.

Fig. 8: LSP processing schemes for Ti-6Al-4V specimens with stress concentrator.

Fig.9: Lifetimes for different regimes of LSP treatments. Five distinct LSP schemes were applied to the stress concentrator zone, differing in laser spot size and overlap ratios: two non-overlapping configurations with 1 mm and 3 mm square spots, a combined approach using sequential 1 mm and 3 mm spots, a 2 mm circular spot with 30% overlap, and a lateral-side treatment strategy targeting the stress concentrator. Fatigue tests were conducted using a Bi-00-100 servo-hydraulic testing machine under uniaxial cyclic loading (cycle asymmetry coefficient R = 0.1, amplitude 10 kN), with crack propagation monitored via the electrical potential drop method. Results (Figure 9) demonstrated that fatigue life enhancement primarily depended on optimal treatment zone selection rather than processing parameters (power, spot shape, overlap, or layering). While parameter adjustments provided minor lifespan improvements, strategic positioning of the treated area increased specimen durability eightfold. This underscores the necessity of mathematical modeling of residual stress distributions when optimizing LSP parameters, particularly for components with complex geometries. 7. Conclusion This study presents an original experimental setup for LSP, combining conventional residual stress evaluation