PSI - Issue 17

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 17 (2019) 324–330

ICSI 2019 The 3rd International Conference on Structural Integrity Fatigue crack growth behavior of laser-shock processed aluminum alloy 2024-T3 ICSI 2019 The 3rd International Conference on Structural Integrity Fatigue crack growth behavior of laser-shock processed aluminum alloy 2024-T3

C.A.R.P. Baptista a, *, M.S.F. Lima b , R. Riva b , R.H.M. Siqueira b a Escola de Engenharia de Lorena, University of São Paulo (EEL/USP), CEP 12602-810, Lorena/SP, Brazil b Photonics Division, Institute for Advanced Studies (IEAv/DCTA), CEP 12228-001, S.J. dos Campos/SP, Brazil C.A.R.P. Baptista a, *, M.S.F. Lima b , R. Riva b , R.H.M. Siqueira b a Escola de Enge haria de Lorena, U iversity of São Paulo (EEL/US ), CEP 12602-810, Lorena/SP, Brazil b Photonics Division, Institute for Advanced Studies (IEAv/DCTA), CEP 12228-001, S.J. dos Campos/SP, Brazil

Abstract Abstract

Laser shock processing (LSP) is a surface modification technique aimed at enhancing the resistance to wear, corrosion and fatigue of structural alloys. Recently, LSP without coating (LSPwC) has been gaining ground, using lasers with lower energies, shorter pulse duration, smaller laser spots and higher surface coverage per shot. In the present work, LSPwC treatment was performed in both sides of pre-cracked compact tension specimens of aluminum alloy 2024-T3. A pulsed (9 ns) Nd:YAG laser system operating in the second harmonic (532 nm) at 10 Hz repetition rate and with pulse energy of about 270 mJ was positioned with a 500 mm focal distance lens in order to conduct LSPwC with an estimated power density of 5.2 GW/cm 2 and two distinct overlapping rates: 50% and 75%. The objective of the work was to investigate the effect of the LSPwC and cyclic load condition on the crack closure and fatigue crack growth (FCG) behavior shown by the samples. Constant amplitude FCG tests were performed with two distinct load ratios: R = 0.2 and R = 0.5. A small increase in the crack closure loads (P cl  1.1-1.2 P min ) and in the number of cycles to crack propagation was evinced for the specimens tested at R = 0.2 compared to the untreated ones, whereas negligible effect was observed in the R = 0.5 tests. Besides, the obtained results indicate that the increase in overlapping rate is not effective for the adopted LSPwC conditions. Laser shock processing (LSP) is a surface modifi atio technique aimed at enha cing the resistance to ear, corrosion and fatigue of structural alloys. Recently, LSP without coating (LSPwC) has b en gaining ground, using lasers with lower energies, shorter pulse duration, smaller laser spots and higher surface coverage per shot. In the present work, LSPwC treatment was performed in both sid s of pre-cracked compact tension specimens of luminum alloy 2024-T3. A pulsed (9 ns) Nd:YAG laser system operating in the second harmonic (532 nm) at 10 Hz repetition rate and with pulse ergy of about 270 mJ was p sitioned with 500 mm focal distance lens in order to conduct LSPwC with an estimated power density of 5.2 GW/ m 2 and two distinct verlapping rates: 50% and 75%. The objective of the work was to investigate the effect of the LSPwC and cyclic load condition on the crack closure and fatigue crack growth (FCG) behavior shown by the samples. Constant amplitude FCG tests were perfor ed with two distinct load ratios: R = 0.2 and R = 0.5. A small increase in the crack closure loads (P cl  1.1-1.2 P min ) and in the number of cycles to cr ck propagation was evinc d for the specimens tested at R = 0.2 compared to the u treated ones, whereas negligible effect was observed in the R = 0.5 tests. Besides, the obtained results indicate that the increase in overlapping rate is not effective for the adopted LSPwC conditions.

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. Keywords: Laser shock processing; Fatigue crack growth; Aluminum alloy 2024. Keywords: Laser shock processing; Fatigue crack growth; Aluminum alloy 2024.

* Corresponding author. Tel.: +55-12-3159-9914; fax: +55-12-3153-3006. E-mail address: carlos.baptista@usp.br * Correspon ing author. Tel.: +55-12-3159-9914; fax: +55-12-3153-3006. E-mail address: carlos.baptista@usp.br

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 10.1016/j.prostr.2019.08.043