Abstract
Laser shock peening (LSP) is a surface modification technique to improve the mechanical properties of metals and alloys, where physical phenomena are difficult to investigate, due to short time scales and extreme physical values. In this regard, simulations can significantly contribute to understand the underlying physics. In this paper, a coupled simulation approach for LSP is presented. A global model of laser–matter–plasma interaction is applied to determine the plasma pressure, which is used as surface loading in finite element (FE) simulations in order to predict residual stress (RS) profiles in the target material. The coupled model is applied to the LSP of AA2198-T3 with water confinement, 3×3mm2 square focus and 20 ns laser pulse duration. This investigation considers the variation in laser pulse energy (3 J and 5 J) and different protective coatings (none, aluminum and steel foil). A sensitivity analysis is conducted to evaluate the impact of parameter inaccuracies of the global model on the resulting RS. Adjustment of the global model to different laser pulse energies and coating materials allows us to compute the temporal pressure distributions to predict RS with FE simulations, which are in good agreement with the measurements.
Highlights
Nowadays, different methods of material surface improvement are available and applied in industry, such as ultrasonic impact treatment [1], shot peening [2] or laser shock peening (LSP) [3]
Based on the identified parameter set at a peak laser intensity of 2.3 GW/cm2 (5 J laser pulse), further Laser shock peening (LSP) cases, such as 3 J laser pulse energy and different coating materials, are investigated
Due to the fact that the radiation absorption by plasma does not strongly depend on the laser intensity, when the intensity is lower than 2.3 GW/cm2 (5 J laser pulse) [27], and considering the fact that the plasma mostly consists of water particles—see Section 2.3.1— the absorption coefficient AP is assumed to remain constant for both 3 J and 5 J laser pulses and the different coating materials used in this study
Summary
Different methods of material surface improvement are available and applied in industry, such as ultrasonic impact treatment [1], shot peening [2] or laser shock peening (LSP) [3]. These techniques allow us to enhance the material performance regarding the fatigue, corrosion and wear resistance of structures and components of, e.g., aircraft or nuclear reactors [3,4]. It has been described as a process where short laser pulses with a high intensity are used to vaporize the surface layer of a target material or a coating. Due to the higher and deeper penetration depth of compressive RS, LSP is a potential substitute for conventional shot peening processes [7]
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