PSI - Issue 75

Hayder Y Ahmad et al. / Procedia Structural Integrity 75 (2025) 245–253 Hayder Y Ahmad et al./ Structural Integrity Procedia (2025)

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This study will conduct a comparative analysis of two mechanical surface enhancement techniques: CSP and LSP. These treatments will be applied to 2024-T4 aluminium alloy to evaluate their effects on surface integrity and mechanical performance. A concise overview of both processes is provided below. 2.1. Conventional shot peening (CSP) Shot peening is one of the most effective mechanical surface treatments for inducing deep compressive residual stresses. This process involves bombarding the material surface with small, high-velocity spherical media, plastically deforming the surface layer. Fig. 1 presents a schematic representation of the core process involved in CSP, extracted from the work of (Shukla et al. 2014):

Fig. 1. Schematic representation of the shot peening process. Adapted from Shukla et al. (2014). • Generates compressive residual stress up to several hundred micrometres deep, improving fatigue life. • Introduces work hardening, enhancing wear resistance. • However, excessive peening may increase surface roughness, which can counteract its benefits. 2.2. Laser shock peening (LSP) LSP is a more advanced alternative to shot peening, producing deeper and more uniform compressive residual stresses with minimal surface roughening. The mechanism of LSP is shown in Fig. 2 extracted from the work of (Higounenc, 2014) and briefly detailed below:

Fig. 2. Schematic representation of the laser shock peening process. Extracted from Higounenc (2014). • A high-energy laser pulse is directed onto the surface, typically with a thin protective overlay (such as water or opaque coating). • Laser energy induces the formation of a plasma, which in turn generates a high-pressure shock wave that plastically deforms the surface layer of the material. This process introduces compressive residual stresses that can penetrate to depths of several hundred micrometres. 3. Experimental work This study investigates the impact of LSP and CSP on the fatigue life of 2024-T4 aluminium alloy, a material widely used in aerospace and structural applications due to its high strength-to-weight ratio. The objective is to evaluate and compare the effectiveness of these surface treatment techniques in enhancing fatigue resistance by inducing beneficial compressive residual stresses, refining the surface microstructure, and reducing crack initiation and propagation.