Simulation-based optimization of laser shock peening process for improved bending fatigue life of Ti–6Al–2Sn–4Zr–2Mo alloy

• Published in: Surface & coatings technology 2013-10, Vol.232, p.464-474
• Main Authors: Bhamare, Sagar, Ramakrishnan, Gokul, Mannava, Seetha R., Langer, Kristina, Vasudevan, Vijay K., Qian, Dong
• Format: Article
• Language: English
• Subjects: Applied sciences; Bending fatigue; Computer simulation; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue; Fatigue life; Finite element method; Laser shock peening; Lasers; Materials science; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Physics; Residual stress; Residual stresses; Shot; Stress concentration; Surface treatments; Ti-6242; Titanium base alloys
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2013.06.003

Laser shock peening (LSP) induced residual stresses significantly affect the high cycle fatigue behavior of certain metals and alloys. Residual stress distribution is a function of various laser parameters (energy, laser pulse width, and spot diameter), the geometry, the material and the laser shot sequencing. Considering the wide range of parameters involved in the LSP process, a numerical approach based on 3D nonlinear finite element method has been employed to explore the relation between the processing parameters and the residual stress distribution. This methodology is applied to a thin coupon of Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) alloy, with a view towards establishing conditions for obtaining through-thickness compressive residual stresses and hence improved bending fatigue life. Material response at very high strain rates in the LSP process is effectively represented using the modified Zerilli–Armstrong material model. The numerical approach is verified by comparison with the experimental results. Effects of laser parameters and laser shot sequencing on final residual stress distribution are studied by performing full scale simulations of LSP patches constituting a large number of laser shots. Based on simulation studies, optimal set of parameters is obtained that produces through thickness compression, which leads to a substantial improvement in bending fatigue life. Fatigue testing results support the recommendations made based on simulation results. •Residual stress of Ti-6242 under practical LSP loading condition is simulated.•A modified Zerilli–Armstrong material model is developed for Ti-6242.•Systematic simulation studies on LSP processing parameters are performed.•LSP sequence can significantly affect the residual stress and fatigue life.•The simulation predictions are supported by experimental results.